eddy current tachometer / effluent

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currents are used to generate heat or electro­magnetic fields for use in such applications as induction heating, the electromagnetic sorting and testing of materials, vibration damping in spacecraft, and various types of instrumentation.

eddy current tachometer A device for mea­suring rotational speed that has been used extensively in automotive speedometers. It consists of a permanent magnet revolving in close proximity to an aluminum disk, which '. is pivoted to turn against a spring. As a mag­net revolves, it induces eddy currents in the disk, setting up torque that acts against the spring. The amount of disk deflection is indi­cated by a moving pointer that is directly coupled to the disk.

EDG Electronic dot generation; method for producing halftones electronically on scan­ners.

edge filter An interference filter that abruptly shifts from transmitting to reflecting over a narrow range of wavelengths.

EDI Electronic data interchange; computer­to- computer exchange of structured transac­tional information between autonomous computers.

edit 1. To rearrange data or information. Edit­ing may involve deleting unwanted data selecting pertinent data applying format techniques inserting symbols such as page numbers and typewriter characters applying standard processes, such as zero suppression and testing data for reasonableness and proper range. Editing is sometimes further distinguished between input editing (rear­ranging source data) and output editing (pre­paring table formats). [ISA-RP55.1-1975 (R1983)] 2. To organize data for subsequent processing on a computer.

editor 1. A routine that performs editing operations. 2. A system program for amend­ing source code programs in high-level lan­guage or assembly languages.

EDO Extended data out; high-performance dynamic random access memory (DRAM).

eductor 1. A device that withdraws a fluid by aspiration and mixes it with another fluid. 2. Using water, steam, or air to induce the flow of other fluids from a vessel. See injector.

EECS Electrical Equipment Certification Ser­vice. British certification laboratory for test­ing the equipment of different vendors to some common standard.

EES Enterprise execution system; software packages to help reconcile top-down busi­ness planning with bottom-up production execution requirements for such functions as

planning, production, and distribution issues. See MES, DES (distribution execution system).

EEx The designation for an explosion-pro­tected electrical apparatus that complies with harmonized CENELEC standards. [ANSI! lSA-12.01.01-1999]

effect A change in output that is produced by some outside phenomena, such as elevated temperature, pressure, hllmidity, or radia­tion. [ISA-RP.67.0;t02-2000]

effective add!'ess: .1.°A Modified address. 2. The address that is actually considered as being used in a particular execution of a computer instruction.

effective bandwidth An operating character­istic of a specific transmission system. It is equal to the bandwidth of an ideal system whose uniform pass-band transmission equals the maximum transmission of the real system. In addition, its transmitted power is the same as the real system for equal input signals that have a uniform distribution of energy at all frequencies.

effective cutoff frequency A transducer characteristic that is expressed as the fre­quency at which the insertion loss between two terminating impedances exceeds the loss at some reference frequency in the transmis­sion band by a specified value.

effective resistance Alternating current resis­tance. It is measured as the power in watts dissipated as heat divided by the current in amperes squared. Effective resistance includes resistance to direct current and resistance caused by eddy currents, hystere­sis, and skin effect.

effective value The root-mean-square value of a cyclically varying quantity. It is deter­mined by finding the average of the squares of the values throughout one cycle and tak­ing the square root of the average.

efficiency 1. The ratio of output to the energy input. The efficiency of a boiler is the ratio of heat absorbed by water and steam to the heat equivalent of the fuel fired. [ISA-77.41-1992] 2. In manufacturing, the average output of a process or production line expressed as a per­centage of its expected output under ideal conditions. 3. The ratio of useful energy that is supplied by a dynamic system to the energy supplied to it over a given period of time. 4. The ratio of the work done by a heat engine to the heat energy absorbed by it, also known as "thermal efficiency."

effluent Liquid waste that is discharged from an industrial processing facility or waste treatment plant.

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effluvium Waste by-products of food or chemical processing.

E format In FORTRAN, an exponential type of data conversion that is denoted by Ew.d, where w is the number of characters to be converted as a floating-point number with d spaces reserved for the digits to the right of the decimal point. For example, Ell.4 yields 000.5432E03 as input, 543.2 internally, and 0.5432E+03 as output.

EFT Electrical fast transient; burst surge . interference to electrical and digital signals. EFTA European Free Trade Association; Aus­

tria, Finland, Iceland, Norway, Sweden, Switzerland.

EGA Enhanced Graphics Adapter (or Array); video standard (for IB\1 PC in 1984); allows sixteen out of possible sixty-four colors to be used; can emulate all modes of earlier CGA, adding 320 x 200, 640 x 200, and 640 x 350 pixels wi th sixteen colors; see eGA, PGA, SVGA,UXGA,VGA,XGA.

E-glass In the construction of glass-bulb-type pH sensors, this term is used for the mem­

·branes of electrodes for processes in which : measurements are to be made in acid media. i .E-glass is suitable for use at higher process

temperatures. See G-, L-, and S-glass. EIA 1393A A user-level format and protocol

(promulgated by the Electronics Industry Association) for the bidirectional transfer of digitally encoded information in a manufac­turing environment.

EIA 485 A format and protocol of the Elec­tronics Industry Association that specifies the electrical characteristics of generators and receivers to be used in balanced digital multipoint systems.

EIA interface A serial word transfer in ASCII characters with RS-232C logic levels, as, for example, between the computer and a man­ualoperator.

EIA-SP 1907B An international building wir­ing standard issued by the Electronics Indus­try Association that formalizes cabling practices, distances, installation practices, and media types.

EIS Extended instruction set; enterprise infor­mation system. Integrated computer data­base for all aspects of corporate business including process and materials manage-

U ment functions across many plant locations. '. ejection 1. The physical removal of an object

from a specific site-such as a cast or molded product from a die cavity by hand, com­pressed air, or mechanical means. 2. The emergency expulsion of a passenger com­partment from ,!n aircraft or spacecraft. 3.

effluvium I elbow meter

The withdrawal of fluid from a chamber by the action of a jet pump or eductor.

ejector A device that utilizes the kinetic energy in a jet of water or other fluid to remove a fluid or fluent material from tanks or hoppers

ejector condenser A direct-contact condenser in which vacuum is maintained by a jet of high-velocity injection water. The condenser simultaneously condenses the steam and dis­charge~ water, condensate, and noncondens­able gases into the cHmbspliere or into the next stage ejector.

elastance The reciprocal of capacitance. elastic chamber The portion of a pres­

sure-measuring system that is filled with the medium whose pressure is being measured and that expands and collapses elastically with changes in pressure. Examples include Bourdon tube, bellows, flat or corrugated diaphragm, spring-loaded piston, or a com­bination of two or more single elements, which may be the same or different types.

elastic collision A collision between two or more bodies in which their internal energy remains constant and the kinetic energy of translation for the combination of bodies is conserved.

elastic scattering A collision between two particles, or between a particle and a photon, in which total kinetic energy and momentum are conserved. ' .

elastomer A material that can be stretched to approximately twice its original length with relatively low stress at room temperature. When the stretching force is released, the material returns forcibly to about its original size and shape.

elastomeric energized liner A resilient elas­tomeric ring under the main liner in a butter­fly valve body is compressed by the disk acting through the main liner. This generates a resilient sealing action between the disk and the main liner. [ANSI/ISA-75.05.01­2000]

elastoresistance The change in the resistance of a material when it is stressed within its elastic limit. A concept used in the design of some sensors.

elbow 1. A fitting that connects two pipes at an angle. The angle is usually 9qo, but it may be any other angle less than 100 . 2. Any sharp bend in a pipe.

elbow meter A pipe elbow that is used as a flow measurement device. A pressure tap is placed at both the inner and outer radius, and the pressure differential caused by dif-

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electrical apparatus category 'ia' / electrical pumping

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ferences in flow velocity between the two flow paths is measured.

electrical apparatus category fiat An electri­cal apparatus that is incapable of causing ignition in normal operation and when a sin­gle fault and any combination of two faults is applied. The safety factors are as follows: l.5-in normal operation and with one fault; La-with two faults. .

electrical apparatus category fib' An electri­cal apparatus that is incapable of causing ignition in normal operation and when a sin­gle fault applied, with the following safety factors: l.5-in normal operation and with one fault; La-with one fault, if the appara­tus contains no unprotected switch contacts in parts that are likely to be exposed to a potentially explosive atmosphere and the fault is self-revealing.

electrical apparatus An item that is applied as a whole or in part to utilize electrical energy. It includes, among others, equipment for generating, transmitting, distributing, storing, measuring, regulating, converting, and consuming electrical energy. It also inclvdes items for telecommunication. [ISA­12.01.01-1999]

electrical circuits low-voltage circuit A cir­cuit that involves a potential of not more than 30 volts. It is supplied by a primary bat­tery or by a standard Class 2 transformer or other suitable transforming device. It can also be supplied by a suitable combination of transformer and fixed impedance that hash output characteristics that comply with Class 2 transformer requirements. A circuit that is derived from a supply source classified as a high-voltage circuit (by connecting resistance in series with the supply circuit to limit the voltage and current) is not considered a low-voltage circuit.

electrical conductivity A material character­istic that indicates the relative ease with which electrons flow through the ma teria!. The usual units of conductivity are %IACS, which relates the conductivity to that of annealed pure copper. Electrical conductivity is the reciprocal of electrical resistivity.

electrical discharge machining A machining method in which stock is removed by melt­ing and vaporization under the action of rapid, repetitive spark discharges through a dielectric fluid flowing in the intervening space between a shaped electrode and the workpiece. It is often referred to by its abbre­viation, EDM. Process variations include electrical discharge grinding and electrical discharge drilling. Also known as "electro­

erosive machining," "electron discharge machining," and "electrospark machining."

electrical/electronic/programmable electronic systems (E/E/PES) When used in this con­text, electrical refers to logic functions that are performed by electromechanical techniques (e.g., electromechanical relay, motor-driven timers, etc.). Electronic refers to logic func­tions that are performed by electronic tech­niques (e.g., solid-s-tate logic, solid-state relay, etc.). Progrqmlf(able Electronic System refers to log·j( that is performed by program­mable or configurable devices (e.g., a pro­grammable logic controller [PLC)), single­loop digital controller [SLDC], etc.). Field devices are not included in E/E/PES. [AN~I/ISA-84.01-1996]

electrical engineering A branch of engineer­ing that deals with the practical applications of electricity, especially the generation, trans­mission, and utilization of electric power by mei:~ns of current flow in conductors.

electrical insulation There are four types of electrical insulation: 1. Basic--Insulation that is applied to live parts to provide basic pro­tection against electric shock. 2. Supplemen­tary-- Independent insulation that is applied in addition to basic insulation to provide protection against electric shock if basic insu­lation fails. 3. Protective (double)--Insulation that comprises both basic insulation and sup­plementary insulation. 4. Reinforced--A sin­gle insulation system that is applied to live parts to protect them against electric shock (it is equivalent to double insulation).

electrically alterable read-only memory (EAROM) A type of computer memory that is nor::nally unchangeable. Its contents can be changed only under special condi­tions.

electrically erasable and programmable read-only memory (EEPROM) Nonvolatile memory that may be electrically erased and reprogrammed.

electrically operated extensions Usually a highly sensitive induction-type device for signaling high or low flows or deviations from any set flow. The device consists of a sensing coil that is positioned around the extension tube of the rotameter. Moving the metering float into the field of the coil causes a low-level sisnal change that is usually amplified to a level suitable for performing annunciator or control functions.

electrical pumping The deposition of energy into a laser medium by passing either an electrical current or discharge or a beam of electrons through the material.

170 _. 'W" .....

electrical resistivity / electric-resistance-type liquid-level detector

electrical resistivity A characteristic of mate­ electric chart drive A clocklike mechanism� rial that indicates that material's relative driven by an electric motor, which advances� resistance to the flow of electrons. The usual a circular or strip chart at a preset rate.� units of resistivity are ohm-m (51) or ohms electric contact Either of two opposing, elec­�per circular-mil foot (U.s. customary). It is trically conductive buttons or other shapes� the reciprocal of electrical conductivity. that allow current to flow in a circuit when�

electrical spacing There are three kinds of they touch each other. They are usually� electrical spacing. 1. Basic: Physical separa­ attached to a spring-loaded mechanism that� tion between conductive parts to provide : is mechanically or electromagnetically oper­�basic protection against electrical shock. 2. ated so as to control whether or not the con­�Supplementary: Physical separation that is tacts touch.� used in additionto basic insulation to protect electriccontroller An assembly of devices� against electric shock if the basic insulation and circuits that turns electric current to an� IIfails. 3. Protective: Increased physical separa­ electrically driven system bff and on in� tion between conductive parts to protect response to a stimulus. In most instances, the� against electric shock (equivalent to double assembly also monitors and regulates one or� insulation). more characteristics of the electric supply­�

electrical steel Low-carbon steel that con­ voltage or amperage, for example.� tains 0.5 percent to 5 percent Si or other electric/electronic extensions A system that� material. Electrical steel is produced specifi­ converts float position into a proportional� cally to have enhanced electromagnetic electric signal (either AC or DC). It may also� properties, which are suitable for making the convert float position into a proportional� cores of transformers, alternators, motors, shift or unbalance in impedance, which is� and other iron-core electric machines. Con- balanced by a corresponding shift in imped­�

. trast with electric steel. ance in the receiving instrument.� electrical terminals There are four types of electric field A condition within a medium�

electrical terminals. 1. Field-wiring terminal: or evacuated space that imposes forces on { Any terminal to which a supply circuit wire stationary or moving electrified bodies in ; is intended to be connected by an installer in direct reIa tion to their electric charges.

the field. 2. Measuring or testing terminal: electric field strength The magnitude of an� An external terminal or connector of the electric field vector.� equipment to which a connection is made to electric heating Any method for converting� serve the eqUipment's function. 3. Measuring electric energy into heat, but especially those� or testing grounded terminal: An external methods that involve resistance to the pas­�terminal of a grounded measuring or testing sage of electric current.� circuit that is internally connected to the electric hygrometer An instrument that uses� eqUipment's protective grounding system an electrically powered sensing means to� and is intended to be connected to the determine the humidity of ambient atmo­�grounded side of the external circuit to sphere.� which it is attached. 4. Protective grounding electric instrument An indicating device for� terminal: A terminal that is connected to the measuring the electrical a ttribu tes of a sys­�eqUipment's protective grounding system tem or circuit. Contrast with electric meter.� and is intended to be externally connected to electricity meter A device for indicating the� earth ground. time integral of an electrical quantity.�

electrical tests There are two types of electri­ electric meter A recording or totaliZing cal tests. 1. Routine test: A test that is per­ instrument that measures the amount of elec­formed on each piece of equipment during tric power that is generated or used as a the production process. 2. Type test: A test function of time. Contrast with electric instru­that is performed on one or more pieces of ment. equipment, which are representative of a electric-resistance-type liquid-level type, in order to determine whether the detector A device for detecting the pres­design, construction, and manufacturing ence of liquid at a given point. It consists of methods comply with the requirements an electric probe that is insulated from the according to standard side of a vessel and positioned so that the

electric boiler A boiler in which electric heat­ end of the probe is at the desired liquid level. ing means serve as the source of heat.� In operation, a small electric voltage is�

impressed between the probe and the vessel.� If liquid exists at the probe level, current�

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electric steel! electrodeposition�

flows in the circuit but does not flow if t11e liquid is below probe level. Simple electrical systems are used when the solution has a resistivity of less than 20,000 ohm-em, but electronic systems can extend the range to 20-million ohm-em. Two probes, widely sep­arated, can be used to control the level between high and low limits or to provide high-level and low-level alarms.

electric steel Any steel that is melted in an electric furnace, which allows close control of composition. Also known as electric-furnace steel. Contrast vvith electrical steel.

electric stroboscope A device that uses an electric oscillator or similar element to pro­duce precisely timed pulses of light. Oscilla­tor freqllency can be controlled over a wide range so that the device can be used to deter­mine the frequency of a mechanical oscilla­tion (for instance, the rpm of a rotating shaft or the frequency of a mechanical vibration) by determining the light-pulse frequency at which the object appears motionless.

electric tachometer An electrically powered instrument for determining rotational speed, usually in rpm.

electric telemeter An apparatus for remotely detecting and measuring a quantity, includ­ing the detector intermediate means, the transmitter, the receiver, and the indicating device. The transmitted signal is conducted electrically into the remote indicating or recording station.

electric thermometer An instrument that uses electrical means to meaSllre and indi­cate temperature.

electric transducer A type of transducer in which all inpllt, output, and intermediate signals are electric waves.

electroacoustic transducer A type of trans­ducer in which the input signal is an electric wave, and the output is a sound wave, or vice versa.

electrochemical cell or battery An electro­chemical system that is capable of storing in chemical form the electric energy it receives and can give it back by reconversion. [ISA­12.16.01-1999 (lEe 79-7 Mod)]

electrochemical cleaning The process of removing soil through the chemical action that is induced by passing an electric current through an electrolyte. Also known as "elec­trolytic cleaning."

electrochemical coating A coating that forms on the surface of a part because of the chemi­cal action that is induced by passing an elec­tric current through an electrolyte.

electrochemical corrosion 1. Corrosion of metal that is caused by current flowing through an electrolyte between anode and cathode areas. [ISA-71.04-1985] 2. Corrosion of a metal because of chemical action induced by electric current flowing in an electrolyte. Also known as "electrolytic cor­rosion."

electrochemical machining (ECM) A machining method in which stock is re!U~ved 1?y ~lect.~~~xt.~~. dissolution when aI! . u.ri.derelectric c~rreht tlows through an elec­trolyteflowing in the space between a tool cathode and the workpiece. Also known as "electrochemical milling" and "electrolytic machining."

electrochemical recording A type of record­ing system in which a signal-controlled elec­tric current passes through a sensitized recording medium, usually in sheet form. This induces a chemical reaction in the medium.

electrochemical transducer A device that uses a chemical change to measure an input parameter and produces an output electrical signal that is proportional to the input parameter.

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1 REFERENCE

GAS IN SIDE ~

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Electrochernical Oxygen Sensor

electrode An electrically conductive member that emits or collects electrons or ions or tha t controls the movement of electrons or ions in the interelectrode space by means of an elec­tric field.

electrode characteristic The relation between electrode voltage and electrode amperage for a given electrode in a system, with the volt­ages of all other electrodes in the system held constant. The electrode characteristic is llSU­ally shown as a graph.

electrode force The force that tends to com­press the electrodes against the workpiece in electric-resistance spot, seam, or projection welding. Also known as "welding force."

electrodeposition Any electrolytic process that reslllts in the deposition of a metal from

172�

electrode voltage I electromechanical transducer

a solution of its ions. It includes processes Most ELs that are used in control systems are such as electroplating and electroforming. ACTFEL devices. Also known as "electrolytic deposition." electrolytic cleaning See electrochemical clean­

electrode voltage The difference in electric mg. potential between a given electrode and the electrolytic corrosion See electrochemical cor­system cathode or a specific point on the rOSlO11.

cathode. The latter is especially applicable electrolytic deposition See electrodeposition. when the cathode is a long wire or filament. electrolytic etching The process of engraving

electrodynamic instrument An electrical a pattern on a metal surface by electrolytic instrument having that has a fixed and a dissolution. movirigcoil, both of which carryall or part of electrolytic grindip.g A combined grinding the current to be measured. If the coils are . and electrochemical tn:ach.ining operqtion in connected in series, the interaction of the which an electrically conductive grinding Ifields induced by the coils produces a torque wheel is made the cathode and the work­that is proportional to the square of the cur­ piece is made the cathode. An electric current rent (as in an AC voltmeter). If the coils are is impressed between them in the presence of connected in parallel, a torque is produced a chemical electrolvte. that is proportional to the product of the two electrolytic hygrometer An apparatus for coil currents (as in an AC ammeter). In both determining the water vapor content of a gas cases, the indication is an effective (rms) by directing it at a known flow rate through a value. Tefion™ or glass tube whose inside has been

electroemissive machining See electrical dis­coated with a thin film of P20S (phosphorus. charge machining. pentoxide), which absorbs water from the

electroforming The process of shaping a flowing gas. The water is dissociated by a component of a thick metal plate on a con­ DC voltage that is impressed on a winding ductive pattern through electrodeposition. embedded in the hygroscopic film. The The part may be used as formed or it may be resulting current represents the number of

I sprayed with molten metal or other material molecules dissociated. A calculation based , on the back to increase its strength. on flow rate, current, and temperature yields

I I. 'electrogalvanizing Coating a metal with the water concentration in ppm.

electrodeposited zinc. electrolytic machining See electrochemical electrograph 1. A tracing that is produced on machining.

prepared sensitized paper or other material electrolytic pickling Removing scale and

I by passing an electric current or electric surface deposits by electrolytic action in a spark through the paper. 2. A plot or graph chemically active solution.

• that is produced by an electrically controlled electrolytic powder A metal powder that is l. stylus or pen. produced directly or indirectly by elec­

electrohydraulic actuator A device that con­ trodeposition. verts electrical energy into hydraulic pres­ electromagnet Any magnet assembly whose sure and into motion. [ANSI/ISA-75.0S.01­ magnetic field strength is determined by the 2000] magnitude of an electric current passing

electroless plating The deposition of a metal through some portion of the assembly. from a solution of its ions by chemical reduc­ electromagnetic 1. Pertaining to phenomena tion. The deposition is induced when the in which electricity and magnetism are basis metal is immersed in the solution, with­ related. 2. When used as a third Modifier per out the use of impressed electric current. standard ISA-37.1-1975 (R1982), electromag­

electroluminescent displays (ELf netic refers to the conversion of a change of ELD) Devices that emit phosphorous glow measurand into an output induced in a con­when they are excited with a small voltage. ductor by a change in magnetic flux, in the Electroluminescent displays are the only absence of excitation. [ISA-37.1-1975 (R1982)] completely solid-state type of liquid crystal electromechanical actuator A device that displays (LCDs) and typically come in two converts electrical energy into motion. versions. Direct-current thick-film devices [ANSI/ISA-75.05.01-2000] are usually used as lamps behind LCDs, and electromechanical transducer A type of alternating-current thin-film ELs (ACTFEL) transducer in which the input signal is an devices are more suitable for high-perfor­ electric wave and the output signal is mance, high-information content displays. mechanical oscillation, or vice versa.

173

electromagnetic compatibility (EMC) / electronic engineering

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electromagnetic compatibility (EMC) An agreement taking effect January 1, 1996, to ensure that no electronic system sold in any member country will generate a electromag­netic field large enough to disturb nearby systems. It also stipulated that all electronic systems would have to be immune from the electromagnetic fields generated by other systems that comply with those same regula­tions. The EMC directive covers frequencies between 9 KHz and 1 GHz. It was initially intended to control the electromagnetic sen­sitivity of virtually all electric and electronic industry products from any EV member or countries included in the European Eco­nomic Area (EEA), with the goal of reducing nontariff barriers to trade. The EMC directive does not mandate a single law for all coun­tries but sets guidelines, which are conse­quently open to interpretation.

electromagnetic field sensitivity The maxi­mum output of a transducer in response to a specified amplitude and frequency of a mag­netic field. It is usually expressed in gauss, equivalent to a stated fraction of 1 g. [ISA­RP37.2-1982 (R1995)]

electromagnetic instrument Any instrument in which the indicating or recording means is positioned by mechanical motion that is con­trolled by the strength of an induced electro­magnetic field.

electromagnetic interference See interference, electromagnetic.

electromagnetic pulse (emp) A type of dis­turbance that leads to noise in radio-fre­quency electric or electronic circuits.

electromagnetic radiation An all-inclusive term for any wave that has both an electric and a magnetic component. The spectrum of electromagnetic waves includes-in order of increasing photon energy, increasing fre­quency, and decreasing wavelength-radio waves, infrar~d, visible light, ultraviolet, x-rays, gamma rays, and cosmic rays.

electromechanics The technology that is associated with mechanical devices and sys­tems that are electromagnetically or electro­staticallv actuated or controlled.

electromagnetic wave A wave in which both the electric and magnetic fields vary periodi­cally, usually at the same frequency.

electrometallurgy The technology that is associated with the recovery and processing of metals using electrolytic and electrical methods.

electrometer An instrument for measuring electric charge, usually by means of the

forces that are exerted on one or more charged electrodes in an electric field.

electrometer tube A high-vacuum tube that can measure extremely small DC voltages or amperages because of its exceptionally low conductance of its control electrode.

electromigration A phenomenon in solid-state microcircuits in which atomic-scale hills and valleys carrying electronic information grow in the microcircuits' thin metal conductors. This problem is more acute with smaller, more densely packed chips.

electron An elementary subatomic particle that has a rest mass of 9.107 x 10-28 g and a negative charge of 4.802 x 10-10 statcoulomb. Also known as a "negatron." A subatomic particle of identical weight and positive charge is termed a "positron."

electron beam A narrow, focused ray of elec­trons that streams from a cathode or emitter and can be used to cut, machine, melt, heat­treat, or weld metals.

electron-beam instrument Any instrument whose operation depends on the use of vari­able electric or magnetic fields, or both, in order to deflect a beam of electrons. The elec­tron beam may be of constant intensity or it may vary in intensity according to a control signal.

electron-beam tube Any of several types of electron tubes whose performance depends on the formation and control of one or more electron beams.

electron device Any device whose operation depends on conduction by the flow of elec­trons through a vacuum, gas-filled space or semiconductor material.

electron emission The ejection of free elec­trons from the surface of an electrode into the adjacent space.

electron gun An electron-tube subassembly that generates a beam of electrons and may additionally accelerate, control, focus, or deflect the beam.

electronic commerce (EC) A business envi­ronment that integrates electronic transfer and automated business systems.

electronic data interchange (EDI) A com­puter-to- computer exchange of structured transactional information between autono­mous computers.

electronic data processing (EDP) Data pro­cessing that is largely performed by elec­tronic equipment.

electronic engineering A branch of engineer­ing that deals chiefly with the design, fabri­cation, and operation of electron-tube or transistorized equipment. Such equipment is

174

electronic heating / electrostatic lens

used to generate, transmit, analyze, and con­ electro-optic effect A change in the refractive trol radio-frequency electromagnetic waves index of a material under the influence of an or similar electrical signals. electric field. Kerr and Pockels effects are,

electronic heating Producing heat by using respectively, quadratic and linear in electric radio-frequency current generated and con­ field strength. trolled by an electron-tube oscillator or simi­ electron volt Abbreviated eV (preferred) or lar power source. Also known as EY. A unit of energy that is equal to the work "high-frequency heating" and "radio-fre­ done in accelerating one electron through an quency heating." electric potential difference of one volt.

electronic mail The use of a large centralized electropainting The electrodeposition of a computer to store messages for user~ of the thin lay~r .Qf paint on metal parts that are electronic mail network. '. . made anodic. Also kn'own as "electro­

electronic measuring equipment Equipment phoretic painting.;' Ithat uses electronic devices to measure or to electrophonic effect An aUditory sensation observe quantities or to supply electrical that results when AC electric current of a cer­quantities for measuring purposes. Elec­ tain amplitude and frequency passes tronic devices are parts or assemblies of parts through an animal's tissues. that use electron or hole conduction in semi­ electrophotography The image transfer sys­conductors, gases, or a vacuum. [ISA-82.03­ tems used in copiers to produce images 1988] using electrostatic forces.

electronic photometer See photoelectric pllO­electroplating The .electrodeposition of a thin tometer. layer of metal on th~ surface of a part that is.

electronic printing Any technology that in contact with a solution or an electrolyte reproduces pages without the use of tradi­ that contains ions of the deposited metal. In

.. tiona I ink, water, or chemistry. most electroplating processes, the part to be ; electronic switch A circuit element that plated is the cathode. The concentration of

causes a start-and-stop or a switching action metal ions in the solution is maintained by electronically, usually at high speeds. placing a sacrificiql anode of the deposited

, electronic transition A transition in which metal in the electrolyte. the electron in an atom or molecule moves electropneumatic controller An electrically from one energy level to another. powered controller in which pneumatic

electron metallography The use of an elec­ devices perform some or all of its basic func­tron microscope to study the structure of tions. metals and alloys. electropolishing Smoothing and polishing a

electronmicroprobe analysis A technique for metal surface by closely controlled electro­determining the concentration and distribu­ chemical action much as in electrochemical tion of chemical elements over a microscopic machining or electrolytic pickling. area of a specimen by bombarding it with electroscope An instrument for detecting an high-energy electrons in an evacuated cham­ electric charge by observing the effects of the ber. X-ray fluorescent analysis is then per­ mechanical force that is exerted between two formed of the secondary X-radiation emitted or more electrically charged bodies. by the specimen. electrospark machining See electrical dis­

electron microscope Any of several designs charge machining. of apparatus that use diffracted electron electrostatic field interference A form of beams to make enlarged images of tiny interference that is induced in the circuits of objects. a device because of the presence of an elec­

electron multiplier tube A type of electron trostatic field. It may appear as com­tube that uses cascaded secondary emission mon-Mode or normal-Mode interference in to amplify small amperages. the measuring circuits. [ANSI/ISA-51.1-1979

electron spectroscopy for chemical analysis (R1993)] (ESCA) An analysis method that measures electrostatic instrument Any instrument the energies of X-ray-induced photoelectrons vvhose operation depends on the forces of emitted from a sample. electrostatic attraction or repulsion between

electron tube Any device whose operation charged bodies. depends on conduction by the flow of elec­ electrostatic lens A set of electrodes arranged trons through a vacuum- or gas-filled space so that their composite electric field acts to within a gastight envelope. focus a beam of electrons or other charged

particles.

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electrostatic memory / elevation

electrostatic memory A memory device that retains information by means of electrostatic charge, usually involving a special type of cathode ray tube and its associated circuits.

electrostatic -microphone An electroacoustic transducer for converting sound into an elec­trical signal by means of the variation in the electrostatic capacitance of the active trans­ducer element.

electrostatic painting A spray-painting pro­cess in which the paint particles are charged by spraying them through a grid of wires . that is held at a DC potential of about 100 kV The parts being painted are connected to the opposite terminal of the high-voltage circuit so they attract the charged paint particles. The process yields more uniform coverage than conventional spray painting, especially at corners, edges, recesses, and oblique sur­faces.

electrostatic precipitator A device for remov­ing dust and other finely divided matter from a flowing gas stream by electrostatically charging them and then passing the gas stream over charged collector plates, which attract and hold the particles.

electrostatic voltmeter An instrument for measuring electrical potential by means of the electrostatic forces between elements in the instrument.

electrostriction transducer A device that con­sists of a crystalline material that produces elastic strain when subjected to an electric field or that produces an electric field when strained elastically. Also known as "piezo­electric transducer."

electrothermal process Any process that pro­duces heat by means of an electric current­using an electric arc, induction, or resistance method-especially when the process requires temperatures higher than those obtained by burning a fuel.

electrothermal recording A form of electro­chemical recording in which chemical change is induced by thermal effects associ­ated with the passage of electrical current.

electrothermic instrument Any instrument whose operation depends on the heating effect associated with the passage of electric current.

element [Comp] 1. A component of a device or system. [ANSl/lSA-51.1-1979 (R1993)] 2. In data processing, one of the items in an array. [Sci] 3. In science, a substance that can­not be decomposed by chemical means into simpler substances.

element, final controlling The forward con­trolling element that directly changes the

value of the manipulated variable. [ANSI/ ISA-51.1-1979 (R1993)]

element, primary The system element that quantitatively converts the measured vari­able energy into a form suitable for measure­ment. Note: For transmitters that are not used with external primary elements, the sensing portion is the primary element. [ANSl/ISA-51.1-1979 (R1993)]

element, reference input The portion of the controlling system that changes the refer­ence-input signal in response to the setpoint. [ANSl/ISA-51.1-1979 (R1993)]

element, sensing The element that is directly responsive to the value of the measured vari­able. It may include the case that protects the sensitive portion. [ANSl/ ISA-51.1-1979 (R1993)]

elementary In object-oriented programming (OOP), something that consists of a Single object, not a compound.

elements of measurement and control systems Functional units or integrated combinations of functional units that ensure the transducing, transmitting, or processing of measured values, control quantities or variables, and reference variables. A valve actuator together with a current-to-pressure transducer, valve positioner, or a booster relay is considered an element that receives the standard pneumatic transmission signal or standard electric current transmission sig­nal. [ANSl/ISA-7.0.01-1996]

elements of process control systems Elements that ensure the transducing, trans­mitting, and processing of measured values, control quantities, controlled variables, and reference variables (transmitters, indicators, controllers, recorders, computers, actuators, signal conditioners). [ANl/ISA-50.1-1982 (R1992)]

elements, feedback Those elements in the controlling system that act to change the feedback signal in response to the directly controlled variable. [ANSl/ISA-51.1-1979 (R1993)]

elements, forward controlling Those ele­ments in the controlling system that act to change a variable in response to the actuat­ing error signal. [ANSI/ISA-51.1-1979 (R1993)]

elevated range See range, suppressed-zero. elevated span See mnge, suppressed-zero. elevated-zero range See mnge, elevated-zero. elevation Vertical distance above a reference

level, or datum, such as sea level. See range, suppressed-zero.

176

Ielevation error / emission characteristic

i.

.,

.. r i' "

..',

~•..

elevation error A type of error in tempera­ture-measuring or pressure-measuring sys­tems that incorporate capillary tubes partly filled with liquid. The error is introduced when the liquid-filled portion of the system is at a different level than the instrument case. The amount of error varies with the dis­tance of elevation or depression.

ELF Extremely low frequency radiation in CRT- based video monitors; see VLF.

elinvar An iron-nickel-chromium alloy that also contains varying amounts of manganese and tungsten, has low thermal expansion, and has almost invariable Modulus of elas­ticity. Its chief uses are for chronometer bal­ances, watch balance springs, instrument springs, and other gauge parts.

ellipsometer An optical instrument that mea­sures the constants of elliptically polarized light. It is most often used in thin-film mea­surements.

elliptically polarized light Light in which the polarization vector rotates periodically, changing in magnitude with a period of 360' so it describes an ellipse. The result of two plane polarized beams of light (each approxi­matelya sine wave) being perpendicular to each other and having a constant phase dif­ference. The resultant planes' polarized wave in the direction of the common beams will describe an ellipse. A special case called "cir­cular polarization" occurs when the ampli­tudes of the two planes' polarized waves are equal, and the phase difference is an odd multiple of _/2.

elliptically polarized wave Anyelectromag­netic wave whose electric or magnetic field vector, or both, at a given point describes an ellipse.

elongation Axial plastic strain. It is usually expressed as a percentage of the original gauge length in a uniaxial tension test to fracture.

ELSI Extra large-scale integration. Integrated circuits that contain more than one million components on a chip.

elute To wash out or remove by dissolving. elutriation The separation of fine, light parti­

cles from coarser, heavier ones by passing a slow stream of fluid upward through a mix­ture so the finer particles are carried along with it.

E-mail Electronic mail; a method for trans­mitting text messages and files digitally over communication links, such as the phone sys­tem.

embedded software Software that is part of the system supplied by the vendor and that

the end user cannot access to Modify. Embedded software is also referred to as "firmware" or "system software." [ANSI/ ISA-84.01-1996]

embedding 1. The process of completely encasing any electrical device by pouring a compound over it in a mold. The enclosed device is then removed from the mold after the compound solidifies. [ISA-12.23.01-1998 (lEC 79-18 Mod)] 2. In OLE (Object Linking and En;tbedqing), embedding means storing an object of one typ~ 'HIe in a file of another type and optionally maintaining linkage from the second file to the file that originally contained the object. An example is an Excel spreadsheet embedded in a WordPerfect document.

embrittlement cracking A form of metal fail­ure that occurs in steam boilers at riveted joints and at tube ends. The cracking is pre­dominantly int~r<;:rystalline.

EMD Equilibrium mode distribution; steady modal state of multimode optical fiber in which the relative power distribution among modes is independent of fiber length.

emergency maintenance An urgent need for repair or upkeep that was unpredicted or not previously planned work. See corrective main­tenance.

emergency shutdown system (ESS) Instru­mentation and controls that are installed for the purpose of taking the process, or specific equipment in the process, to a safe state. This does not include instrumentation and con­trols that are installed for nonemergency shutdowns or routine operations. Emergency shutdown systems may include electrical, electronic, pneumatic, mechanical, and hydraulic systems (including those systems that are programmable). Other common terms used for emergency shutdown systems include "safety instrumented system" (SIS), "safety shutdown systems" (SSD), "protec­tive instrument systems," and "safety inter­lock systems." [ANSI/ISA-91.01-1995]

emery An abrasive material composed of pulverized, impure corundum. It is used in various forms, including cloth or paper, and combines an adhesive-bonded layer of emery grains and compacted, emery-binder mixtures that are shaped into cakes, sticks, stones, grinding wheels, and other imple­ments.

emission characteristic The relation between the rate of electron emission and some con­trolling factor-the temperature, voltage, or current of a filament or heater, for instance-

I

177

emissivity / enclosure

for a specific element of a system, all other factors being held constant.

I

emissivity 1. A material characteristic that is determined as follows. The ratio of radi­ant-energy emission rate that is solely a result of temperature for an opaque, polished surface of a material is divided by the emis­sion rate for an equal area of a blackbody at the same temperature. 2. The rate at which electrons are emitted from a solid or liquid surface when additional energy is imparted to the system by radiant energy, such as heat or light, or by energetic particles, such as a beam of electrons.

EMI susceptibility The level or degree to which a device is vulnerable to electromag­netic interference.

emittance An alternative term for emissivity. emulate To imitate one system with another

such that the imitating system accepts the same data, executes the same programs, and achieves the same results as the imitated sys­tem.

emulator 1. A device or program that emu­lates, usually by microprogramming the imi­tating system. Contrast with simulate. 2. A computer that behaves very much like another computer by means of suitable hard­ware and software.

emulsifier A substance that can be mixed with two immiscible liquids to form an emulsion. Also known as "disperser" and "dispersing agent."

emulsion characteristic curve A graph of the relative transmittance of a developed photo­graphic or radiographic emulsion versus exposure. Alternatively, a graph of a function of transmittance versus a function of expo­sure.

enable 1. To restore a computer system to ordinary operating conditions. 2. To "arm" a software or hard ware element to receive and respond to a stimulus. 3. To allow the pro­cessing of an established interrupt. 4. To remove a blocking device, that is, a switch, to permit operation. Contrast with disable. See also arm.

enamel 1. A type of oil paint that contains a finely ground resin and that dries to a harder, smoother, glossier finish than other types of paint. 2. Any relatively glossy coating, but especially a vitreous coating on metal or ceramic, which is obtained by covering it with a slurry of glass frit and firing the object in a kiln to fuse the coating. Also known as "glaze" and "porcelain ename!."

encapsulated body All surfaces of the body are covered by a continuous surface layer of

a different material, usually an elastomeric or polymeric materia!. [ANSI/ISA-7S.0S.01­2000]

encapsulated body liner In a butterfly valve body, all the surfaces of the body are covered by a continuous surface layer of a different material, usually an elastomeric or plastic material. A soft elastomer behind a harder encapsulating material may be used to pro­vide interference for disk and stem sealing areas. [ANSI/ISA-7S.0S.01-2000]

encapsulation [Safe] 1. 1;0 safety contexts, an international term that describes a type of pro­tection in which the parts that could ignite an explosive atmosphere by either sparking or heating are enclos~d il} an encapsulant so this ignition canno~occur. CENELEC refers to this type of protection as "Ex m" in draft standard ENS0028. Note: Encapsulation is the potting or casting of electrical components with epoxy, elastomer, silicone, asphaltic, or similar compounds for the purpose of excluding moisture or vapors. Encapsulated compo­nents are not necessarily hermetically sealed. [ANSI/ISA-12.00.01-1999 (IEC 60079-0 Mod)] 2. The process of applying the compound to enclose any electrical device(s) by suitable means such as embedding or potting. [A SI/ ISA-12.23.01-1998 (lEC 79-18 Mod)] 3. In object-oriented programming (OOP), the inclusion of data structures and procedures in a single entity and the isolating (or hiding) of those workings. This leaves interfaces clean and defined for Modularity. 4. A pro­cess of transmitting network traffic that encloses one protocol within another.

encapsulation "m" A type of protection in which the parts that could ignite an explo­sive atmosphere by either sparking or heat­ing are enclosed in a compound in such a way that this explosive atmosphere cannot be ignited. [ANSI/ISA-12.23.01-1998 (IEC 79­18 Mod); ANSI/ISA-12.01.01-1999]

encipher See encode. enclosure 1. A part that protects equipment

against certain external influences and, in any direction, protection against direct con­tact. It may also provide protection against the spread of fire. [ANSI/ISA-82.02.01-1999 (IEC 1010-1 Mod)] 2. All the walls that sur­round the live parts of electrical apparatuses, including doors, covers, cable entries, rods, spindles, and shafts. These enclosures ensure the degree of protection that is provided by the enclosure of the electrical apparatus. Note 1: This definition differs from that of IEC 60079 ISA-12.00.01 (IEC 60079-0 Mod) because it recognizes that an intrinsically

178 ___ cT'

enclosure type I endothermic reaction

r safe apparatus may not be in a single enclo­ encrustation The buildup of slag, corrosion sure and that it is not dependent on its enclo­sure for primary protection. Note 2: The enclosure may not be physically the same for protecting an apparatus from live parts ver­sus protecting it from the ingress of solid for­eign bodies and liquids. Note 3: Designating the surfaces that form the boundaries of the enclosure is the responsibility of the manu­facturer. [ISA-12.02.01-1999; lSA-12.00.01­1999 (IEC 60079-0 Mod)] 3. A framework or shell, .or a combination of these, that pro­vides the environment for containing the control equipment and instrumentation that constitute a control center.

enclosure type A North American system of rating the standard levels of protection pro­vided to electrical apparatus by enclosures. The levels of protection by these enclosure types are to (1) persons against contact with live or moving parts inside the enclosure, (2) the apparatus against the ingress of solids and/or liquids, (3) the apparatus against the deleterious effects of corrosion, and (4) the apparatus against the damage caused by the formation of external ice. This enclosure type is in addition to (and not an alternative to) the types of protection needed to safeguard against ignition in hazardous (classified) locations. Definitions of these enclosure types are found in UL 50 or NEMA 250. See

I also degree of protection. [ISA-12.01.01-1999]

i encode 1. To apply a code, frequently one that consists of binary numbers, to represent individual characters or groups of characters in a message. Synonymous with "encipher." 2. To represent computer data in digital form. 3. To substitute letters, numbers, or charac­ters for other numbers, letters, or characters, usually in order to intentionally hide the meaning of the message except to certain individuals who know the enciphering scheme.

encoder 1. A device that is capable of trans­la ting from one method of expression to another method of expression. For example, an encoder might translate a verbal message, "add the contents of A to the contents of B," into a series of binary digits. Contrast with decoder. 2. A device that transforms a linear or rotary displacement into a proportional digi­tal code. 3. A hardware device that converts analog data into digital representations. .'. ~t·

I encoding/decoding The process of organiz­ing information into a format suitable for transmission and then reconverting it after the transmission.

179

products, and biological organisms such as barnacles or other solids on a structure or exposed surface.

encryption The process of converting data into codes that cannot be read without a key or password.

end In computer programming, a word tha t indicates the completion of a program struc­ture.

end around carry A carry from the most-sig­nificant digit place to ttl€ least-significant digit place:

end connection The configuration that is pro­vided in order to make a connection with the pipe. [ANSI/ISA-75.05.01-2000]

end connections, flanged End connections that incorporate flanges that mate with the corresponding flanges on the piping.

end connections, split-clamp End connec­tions of various proprietary designs that use split clamps in order to apply gasket or mat­ing surface loading.

end connections, threaded End connections that incorporate threads, either male or female.

end connections, welded End connections that have been prepared so they can be welded to the line pipe or other fittings. Such connections may be butt weld (BW) or socket weld (SW).

end device The last device in a chain of devices that performs a measurement func­tion. The end device is the one that performs the final conversion of a measured value into an indication, record, or control-system input signal. See transducer.

ENDEC Encoder/decoder; term used in the disk industry for digital circuitry that per­forms manipulations similar to those a video codec does for video signals, in bits going to and from disk drive. See cadee.

end element In process control, a device that causes a change in a process, such as a valve, motor drive unit, silicon-controlled rectifier (SCR), and the like. Also finnl deviceJinnl con­trol device.

end instrument See end device and transducer. end-of-file (EOF) A magnetic marker on a

reel of magnetic tape that signifies where a data file ends.

end of tape (EOT) A unique reflective marker near the end of a reel of magnetic tape to warn the computer that the end is approaching.

endothermic reaction A reaction that occurs with the absorption of heat.

ena play I ennancement, senal aata

II

end play Axial movement in a shaft-bearing assembly as a result of clearances within the assembly.

end points 1. The outputs at the specified upper and lower limits of the range. Note: Unless otherwise specified, end points are averaged during anyone calibration. [ISA­37.1-1975 (R1995)] 2. The limits of a full-scale calibration curve.

end-scale value The value of an actuating electrical quantity that corresponds to the high end of the indicating or recording scale on a given instrument.

endurance limit The maximum stress below which a material can presumably withstand an infinite number of stress cvcles. If the stress is not completely reversed, the mini­mum stress also should be given. See also fatiguc strength.

end point In titration, an experimentally determined point, close to the equivalence point, that is used as the signal to terminate titration. The end point is used instead of the equivalence point in most calculations, and corrections for the error between the end point and equivalence point usually are not applied.

end-point control The exact balancing of pro­cess inputs that is required to satisfy stoichio­metric demands.

end-point line The straight line between the end points. [ISA-37.1-1975 (R1995)]

end-point linearity The linearity of the object, taken between the end points of cali­bration.

end-to-end dimension See face-tolace dimen­sion and ccnter-to-end dimension". [ANSI/ISA­75.05.01-2000]

end-user interface A device through which computer application program(s) and lor instrumenL1tion and measurement device(s) provide information to the appropriate peo­ple. See also CUI.

energized Electrically connected to a source of potential difference. [ISA-12.01.01-1999]

energize to trip Circuits of a safety instru­mented system (SIS) in which the outputs and devices are deenergized under normal operation. The application of power (e.g., electricity or air) causes a trip action. [ANSI! ISA-84.01-1996]

energy The capacity of a body for doing work or its equivalent. Energy may be classified as potential or kinetic, depending on whether it is associated with bodies at rest or bodies in motion. It mav also be classified as chemical, electrical, ele~tromagnetic, electrochemical, mechanical, radiant, thermal or Vibrational,

or any other type, depending on its source or nature.

energy balance The balance that relates the energy in and energy out of a process. In a distillation column, the energy balance manipulative variables are reflux and boilup.

energy beam An intense ray of electromag­netic radiation, such as a laser beam, or of nuclear particles, such as electrons. An energy beam can be used to test materials or to process them by cutting, drilling, forming, welding, or heat tre'a:ting.

energy density Light energy per unit area, expressed in joules per square meter. Equiva­lent to the radiometric term irradiance.

energy exchanger A generic term for any of several devices whose primary function is to transfer energy from one medium to another. Examples include heat exchangers, boilers, and electrical transformers.

engine A machine whose chief purpose is to convert various forms of energy, such as heat or chemical energy, into mechanical power, and to perform work by imparting mechani­cal force and motion to other mechanisms.

engine block See cylinder block. engine lathe A manually operated lathe

whose headstock is driven by a gear train, by a stepped pulley mechanism, or by a combi­nation of gears and pulleys.

engineering analysis system A system that performs computer-based analyses for the purpose of evaluating CAD (computer-aided design) deSigns and Models.

engineering plastics Plastics rna terials tha t are suitable for making into structural mem­bers and machine elements.

engineering time The total machine down­time that is necessary for routine testing (good or bad), for machine servicing as a result of breakdowns, or for preventive ser­vicing measures. This includes all test time (good or bad) after a breakdown and the sub­sequent repair of preventive servicing. Syn­onymous with "servicing time."

engineering units Terms of data measure­ment, such as degrees Celsius, pounds, ~rams,

and so on. [ISA-TR50.02, Part 9-2000] Engler viscosity A standard time-based vis­

cosity scale used primarily in Europe. enhancement, serial data A method whereby

a continuous string of logical ONEs or ZEROs is Modified to introduce bit transi­tions that make it possible to synchronize bits for recording purposes. Serial data enhancement also preserves bandwidth. For example, in an incoming serial data stream, a number of words are all logic ZEROES and

180

Enhanced Performance Architecture (EPA) / entry point

, are therefore a DC level that the bit synchro­ ratus, considering faults and applicable fac­nizer cannot synchronize on. The data are enhanced by making the least-significant bit of the words a logic ONE.

Enhanced Performance Architecture (EPA) EPA is an extension to MAP (Manu­facturing Automation Protocol) that makes possible low-delay communication between nodes on a single segment.

ENlAC Electronic Numerical Integrator and Computer; repu.ted to be the first electronic

i

1 t computer. Introduced at the University of

Pennsylvania in 1945 by John W. Mauchly and J. Presper Eckert Jr. Mauchly had visited

:1 John V. Atanasoff in 1941 to examine his 1939 prototype electronic vacuum-tube computer, which was the first to use the binary system and could solve equations containing twenty-nine variables. ENIAC consisted of ,. 30 tons of 18,000 vacuum tubes, 500,000 sol­

,~ dered joints, 70,000 resistors, and 10,000 ;~ capacitors. I" ENQ A control character that is used to ~iI~ request the identification or the status of a ';t .' remote device.Ii .enter key The key on a computer terminal k that is pressed to enter data into a computer. Ii enterprise 1. An organization that coordi­111 nates the operation of one or more sites. :s :1' [A SI/ISA-88.01-1995] 2. Any undertaking, '. venture, initiative, or business organization

with a defined mission. [ANSI/ISA-95.00.01­, 2000]

.".. . enthalpy The sum of the internal energy of a system plus the product of the system's vol­ume multiplied by the pressure exerted on the system by its surroundings. Also known as heat content, sensible hent, and "total heat."

entities Design elements at the lowest stage of complexity, such as lines or arcs, which are joined to make symbols or groups. See also primitives.

entity 1. A particular thing, such as a person, place, process, object, concept, association, or event. [ISA-TR50.02, Part 9-2000] 2. An active element within an OSI layer (e.g., Token Bus MAC is an entity in the Layer 2).

entity concept A concept that allows an intrinsically safe apparatus to be intercon­nected with an associated apparatus that has not specifically been examined in such a combination. The criteria for interconnection is that the voltage (Vmax) and current (lma,) that intrinsically safe apparatuses can receive and remain intrinsically safe, considering faults, must be equal to or greater than the voltage (VDC or VI) and current (Isc or It) levels that can be delivered by the associated appa­

tors. In addition, the maximum unprotected capacitance (C;) and inductance (L;) of the intrinsically safe apparatus, including inter­connecting wiring, must be equal to or less than the capacitance (C ) and inductance (La)athat can safely be connected to the associated apparatus. If'these criteria are met, then the combination may be connected without com­promising intrinsic safety. Additional infor­mation on the entity <:;oFlcept is provided in ANSI/ISA-RPI2.6-1995.. fANSI/ISA­12.01.01-1999] II

entity evaluation A method for determining acceptable combinations of intrinsically safe apparatuses and associated apparatuses that have not been investigated in such combina­tions. [ISA-12.02.01-1999; ANSI/ISA-RPI2.6­1995] See rntity collcept.

entrainment The process by which steam conveys particles of water or solids from the boiler water.

entropy [Comm] 1. In communications, a measure of the absence of information about a situation or, equivalently, the uncertainty associated with the nature of a situation. [Sci] 2. In scientific contexts, entropy is a function of the state of a thermodynamic system whose change in any differential reversible process is equal to the heat that the system absorbs from its surroundings divided by the absolute tem­perature of the system. Also known as "ther­mal charge."

entry Any item of computer data that is to be stored and processed.

entry, direct A method for connecting an electrical apparatus to the external circuits by means of the connecting facilities that lie inside the main enclosure or in a terminal compartment that has a free opening to the main enclosure. (lEV 426-04-07) [ISA­12.01.01-1999]

entry, indirect A method for connecting an electrical apparatus to the electrical circuits by means of a terminal box or a plug-and­socket connection that is external to the main enclosure. (lEV 426-04-08) [ISA-12.01.01­1999]

entry conditions The initial data and control conditions that must be satisfied in order for a given routine to execute successfully.

entry data The initial data that is required for a given routine to execute successfully. See entry conditions.

entry name The alphanumeric name given to an entry point. See entry point.

entry point In a routine, any place to which control can be passed.

181

envelope / equipment entity

envelope Generally, the boundaries of an enclosed system or mechanism. Specifically, the glass or metal housing of an electron tube, or the glass enclosure of an incandes­cent lamp. Also known as bulb.

environment The ambient conditions (including temperature, pressure, humidity, radioactivity, and corrosiveness of the atmo­sphere) surrounding the valve and actuator. Also, the mechanical and seismic vibration that is transmitted through the piping or the

". ' .. heat that is radiated toward the actuator from the valve body. [ANSI/ISA-75.05.01­2000]

~ environmental area See area, environmental.

I environmental conditions The specified f external conditions (shock, vibration, tem­.

I ,

perature, etc.) to which a transducer may be exposed during shipping, storage, handling, and operation. [ISA-37.1-1975 (R1982)]

environmental conditions, operating The

I environmental conditions in which a trans­ducer must perform in some specified man­ner. [ISA-37.1-1975 (R1982)]

environmental engineering A branch of engineering that deals with the technology for controlling the surroundings humans live in, especially the control or mitigation of the contamination or degradation of natural resources such as air quality and water purity.

environmental influence See operating influ­ence.

environmental test Any laboratory test that is conducted under conditions that simulate the expected operating environment in order to determine the effect of the environment on a component's operation or service life.

EOF marker In data processing, a code that is written after the last record of a file to indi­cate the end of that file. See end-of-file and end of tape.

EP lubricant "Extreme-pressure lubricant." An oil or grease that contains additives that enhance the ability of the lubricant to adhere to a surface and reduce friction under high bearing loads.

epoxy adhesive An adhesive made of epoxy resin.

EPP Enhanced parallel port; digital communication that communicates in both directions.

Eppley pyrheliometer A thermoelectric device for measuring direct and diffuse solar radiation. Radiation is directed onto two con­centric silver rings, the outer covered with magmesium oxide and the inner covered with lampblack. A thermopile is used to

determine the difference in tempera ture between the two rings.

EPRI Electric Power Research Institute; research consortium of 660 member utilities in the United States.

EPS Encapsulated PostScript; format for sav­ing bit-mapped graphics in electronic mem­ory; used for exchanging data between computers.

•. equal-percentage .characteristic An inherent flow character.istic which, for equal incre­ments of rated,tr~",:el, will ideally give equal percentage changes of the flow coefficient (Cv or KJ. [ANSI/ISA-75.05.01-2000]

equalization Compensation for the increase of attenuation with frequency. Its purpose is to produce.a..f.lat frequency response.

equalizer 1. A device that connects the parts of a boiler so as to equalize pressures. 2. The electronic circuit in a tape reproducer whose gain across the spectrum in question com­pensates for the unequal gain characteristic of the record/reproduce heads. This com­pensation provides "equalized" gain across the band.

equilibrium state Any set of conditions that results in perfect stability. Examples include mechanical forces that completely balance each other and do not produce acceleration, or a reversible chemical reaction in which there is no net increase or decrease in the concentration of reactants or reaction prod­ucts.

equipment 1. An assembly of electrical or electronic components or circuits that is intended to perform a complete function apart from being a substructure of a system. 2. A generic term for any apparatus, assem­bly, mechanism, or machine; for a group of units constructed Similarly; or for a group of units that perform similar functions.

equipment class A means for describing a group of equipment that has similar charac­teristics for the purposes of scheduling and planning. [ANSI/ISA-95.00.01-2000]

equipment compatibility The characteristic of computers by which one computer may accept and process data prepared by another computer without converting or Modifying codeMod.

equipment control The equipment-specific functionality that provides the actual control capability for an equipment entity, including procedural, basic, and coordination control, and that is not part of the recipe. [ANSI/ISA­88.01-1995] See recipe.

equipment entity A combination of physical processing and control equipment and

182 - K':'l

. ....

equipment failure I error

equipment control that is grouped together ERA ERA Technology Ltd. (Britian); British so as to perform a certain control function or certification laboratory for testing the equip­set of functions. [ANSl/ISA-88.01-1995] ment of different vendors to some common

equipment failure A fault in the equipment, standard. excluding all external factors, that prevents erasable programmable read-only memory continued performance. (EPROM) A read-only memory in which

equipment Module A functional group of stored data can be erased by ultraviolet light equipment that can carry out a finite number or other means and reprogrammed bit by bit of specific, minor processing activities. Note with pulses of the appropriate voltage. 1: An equipment Module is typically cen­ erasable storage 1. A storage device whose tered around a piece of process equipment (a data can be altered during the course of a weigh tank, a process heater, a scrubber, etc.). cqmputatio~)or' exam-ple,.magnetic tape, This term applies to both the physical equip-" drum, and cores. 2. An area of storage used Iment and the equipment entity. Note 2: for temporary storage.. Examples of minor process activities are dos­ erase [Comp] 1. In computing, to change all ing and weighing. [ANSl/ISA-88.01-1995] the binary digits in a digital computer stor­

equipment operation An operation that is age device into binary zeros. [Eng] 2. In engi­part of equipment control. [ANSl/ISA-88.01­ neering, to remove recorded material from 1995] magnetic tape by passing the tape through a

equipment phase A phase that is part of strong, constant magnetic field or through a equipment control. [ANSl/ISA-88.01-1995] high-frequency alternating magnetic field.

equipment procedure A procedure that is erg The unit of energy in the centimeter­part of equipment control. [ANSl/ISA-88.01­ gram-second (CGS) system. It is the amount 1995] of energy that is consumed (work) when a

·equipment test A test to verify that individ­ force of one dyne is applied through a dis­ual instrument items operate in accordance tance of one centimeter. with the assembly drawings. Note: This test ergonomic design Equipment or a work does not include signal direction or calibra­ environment that is designed to suit human tion. capabilities and psychology.

equipment unit procedure A unit procedure ergonomics The science of designing that is part of equipment control. [ANSl/ machines and work environments to suit the

. , ISA-88.01-1995] needs of people. equivalence point The point on the titration EROM Erasable read-only memory; entire

curve at which the acid ion concentration memory can be erased with exposure to equals the base ion concentration. ultraviolet light so that a new program can

equivalent binary digits The number of replace an old. binary digits that are required to express a erosion 1. Deterioration by the abrasive number in another base to the same preci­ action of fluids, usually accelerated by the sion. For example, it takes approximately 3 presence of solid particles in suspension. 1/3 binary digits to express in binary form [ISA-71.04-1985] 2. The wearing away of each digit of a decimal number. For binary­ refractory or metal parts by gas- borne dust coded decimal notation, the number of particles. 3. The progressive destruction of a binary digits required is usually four times structural member by the abrasive action of a the number of decimal digits. moving fluid, often one containing solid par­

equivalent evaporation Evaporation that is ticles in suspension. If the fluid is a gas, ero­expressed in terms of the pounds of water at sion may be caused by liquid droplets a temperature of 212°F that are evaporated carried in the moving gas stream. into dry saturated steam at 21tE erosion-corrosion The progressive destruc­

equivalent network A network that can per­ tion of a structural member by the combined form the functions of another network under effects of corrosion and erosion acting simul­certain conditions. The two networks mav be taneously. of different forms-one mechanical and ~ne erosion-resistant trim Valve trim that has electrical, for instance. been designed with special surface materials

equivalent volume For a gas enclosed in a or geometry to resist the erosive effects of the rigid cavity the volume that would give the fluid flow. [ANSl/ISA-75.05.01-2000] same acoustical input impedance as that of error 1. In process instrumentation, the alge­the piezoelectrical sound-pressure trans­ braic difference between the indication and ducer. [ISA-37.10-1982 (RI995)] the ideal value of the measured signal. It is

183

error, environmental/error-correcting code�

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the quantity that when algebraically sub­tracted from the indication gives the ideal value. Note: A positive error denotes that the indication of the instrument is greater than the ideal value: error = (indication) - (ideal value). See ANSI/ISA-S51.1-1979 (R1993). [ANSI/ISA-67.04.01-2000; ISA-RP67.04.02­2000] 2. The algebraic difference between the indicated value and the true value of the measurand. Note 1: Error is usuallv expressed in terms of the percentage of the

. full-scale output, but sometimes in terms of the percentage of the output reading of the transducer. Note 2: A theoretical value may be specified as true value. [ISA-37.1-1975 (R1982)] 3. Error is the general term that refers to any deviation of a computed or a measured quantity from the theoretically correct or true value. 4. That part of the error that is caused by a particular identifiable cause, for example, a truncation error or a rounding error. In a restricted sense, error is that deviation that is caused by unavoidable random disturbances or by the use of finite approximations to what is defined by an infinite series. 5. In a single automatic control loop, the set point minus the controlled variable measurement.

error, environmental An error that is caused by a change in a specified operating condi­tion from a reference operating condition. See operating influence. [ANSI/ISA-51.1-1979 (R1993)]

error, frictional The error in a device that is caused by the resistance to motion presented by contacting surfaces. [ANSI/ISA-51.1-1979 (R1993)]

error, hysteresis See hysteresis. error, inclination The change in output that

is caused solely by an inclination of the device from its normal operating position. [ANSl/ISA-51.1-1979 (R1993)]

error, mounting strain The error that results from the mechanical deforma tion of an instrument when it is being mounted and connected to other devices. See also error, inclination. [ANSl/ISA-51.1-1979 (R1993)]

error, position The change in output caused by mounting or setting an instrument in a position different from that at which it was calibrated. See also error, inclination. [ANSl/ ISA-51.1-1979 (R1993)]

error, span The difference between the actual span and the ideal span. Note: It is usually expressed as a percentage of ideal span. [ANSI/ISA-51.1-1979 (R1993)] Span error, when displayed on an input/ output calibra­tion graph, is represented by an as-found line

that is not parallel to the ideal line, that is, the slopes of the two lines are different.

error, systematic When a number of mea­surements are made under the same condi­tions of the same value for a given quantity, a svstematic error either remains constant in absolute value and sign or varies according to a definite law when the conditions change. [ANSl/ISA-51.1-1979 (R1993)]

error, zero In process instrumentation, the error of a device that-i-s.operating under specified conditions-oJ use, when the input is at the lower-range ~alue. It is usually expressed as percentage of ideal span. [ANSl/ISA-51.1-1979 (R1993)] Zero error, wh~n·.disp~aye~ on an input/ output calibra­tion graph, IS r~prisented by an as-found line that is parallel to the ideal line. The zero error may produce a constant offset through­out the range of the instrument.

error band The band of maximum deviations of the outplit values from a specified refer­ence line or curve because of factors attri.but­able to the transducer. Note 1: The band of allowable deviations is usually expressed as "± [number] percent of full scale output," whereas in test and calibration reports the band of maximum actual deviations is expressed as "+ [number] percent, - [num­ber] percent of full-scale output." Note 2: To include repeatability, the error band should be specified as being applicable over at least two calibration cycles and verified accord­ingly. [ISA-37.1-1975 (R1982)]

error burst In data transmission, a sequence of Signals that contains one or more errors but is counted as only one unit in accordance with some specific criterion or measure. An example of such a criterion is that if three consecutive correct bits follow an erroneous bit, an error burst is terminated.

error checking A form of data quality assur­ance that is usually attempted by calculating some property of the data block before trans­mission. The resulting property or check character is also sent to the receiver, where it may be inspected and compared with a recal­culated value based on the received data.

error control An arrangement that detects the presence of errors. In some systems, refine­ments are added that will correct detected errors, either by performing operations on the received data or by requesting retrans­mission from the source.

error-correcting code 1. A code that is stored along with data in a semiconductor memory to help detect and correct errors. 2. A code in which each acceptable expression conforms

184

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to specific rules of construction, which also define one or more equivalent and accept­able expressions. The result will be one of its equivalents, and thus the error can be cor­rected.

error curve A graphical representation of errors that is obtained from a specified num­ber of calibration cycles. [ISA-37.1-1975 (R1982)J

error-detecting code A code in which each expression conf~rms to specific rul~s of con­struction. If certain errors occur in an expres~

sion, the resulting expression will not conform to the rules of construction, and thus the presence of the errors is detected. Synonymous with "self-checking code."

error detection and correction A term that is sometimes used for "self-correcting mem­ory" (code, transmission). Software that looks for specific rules of construction, detects expressions that do not conform, and substitutes an equivalent form. See self-cor­recting memory.

error-detection routine A routine that is used . to detect whether or not an error has

. occurred, usually without special provision to find or indicate its location.

error indication Ideal value. ~rror maximum (data processing) The maxi­.� mum error ("EMAX") of the analog sub­

system. It is defined as the deviation that exists between the true value of the input sig­nal and the particular output reading within the distribution of output readings that is furthest displaced from the true vahle. [ISA­RP55.1-1975 (R1983)J

error message 1. An audible or visual indica­tion of a software or hardware malfunction, or a nonacceptable data entry attempt. 2. In com­puting, some terse, baffling remark used by programmers to place blame on users for the shortcomings of a program.

error range 1. The range of all possible values of the error of a particular quantity. 2. The difference between the highest and the low­est of these values.

error ratio The ratio of the number of data units in error to the total number of data units.

error signal The output of a comparing ele­ment. See "signal, error."

error squared A control technique in which the square of the error is introduced in the error term of a linear algorithm so as to pro­duce a nonlinear correction.

ESC "Escape." A digital communication con­trol character that is used to provide addi­tional control functions. It alters the meaning

error curve / Ethernet lOBase5

of a limited number of continuously follow­ing bit combinations, usually to take control of a computer away from a program or to stop a program.

escape key A key on a computer keyboard that returns the operator to the prior step in a command sequence.

escapement A ratchet device that permits motion only in one direction. An example is the device that controls mot'on in the works of a mechanical watch or clock.

•. :.~escutcbeon A"aecorat-i\'e' shield, flange, or" border around a panel-mounted part such as a dial or control knob. Also known as an "escutcheon plate."

Etalon A type of Fabry-Perot interferometer in which the distance between two highly reflecting m;rrors is fixed. It is used to sepa­rate light in different wavelengths when the wavelengths are closely spaced.

etch cleaning &e~Oving soil by electrolytic or chemical action; which also removes some of the underlying metal.

etch cracks Shallow cracks in the surface of hardened steel caused by the hydrogen embrittlement that sometimes occurs when the metal comes into contact with an acidic environment.

etching 1. The controlled corrosion of a metal surface so as to reveal its metallurgical struc­ture. 2. The controlled corrosion of a metal part so as to create a design. The design may consist of alternating raised and depressed areas, or it may consist of alternating pol­ished and roughened areas, depending on the conditions and corrodent used.

Ethernet A popular local area network (LAN) design, invented by Robert Metcalfe of Xerox Corporation in the mid-1970s, and used as a standard by DEC and Intel. Characterized by 10 Mbps baseband transmission over shielded coaxial cable and employing CSMA/CD as the access control mechanism. The Ethernet is standardized in the IEEE specification IEEE 802.3. Ethernet uses error­detection procedures but no error correction, but unlike IEEE 802.3 it has Signal quality error /heartbeat signal from transceiver to node. Ethernet allows audio and video infor­mation to be carried as well as computer data.

Ethernet lOBASE2 An implementation of the IEEE 802.3 standard, known as "thinnet." It operates over thin coaxial cable at 10 Mbps baseband.

Ethernet lOBASE5 An implementation of the IEEE 802.3 standard, known as "standard

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Ethernet" or "thicknet." It operates over thick coaxial cable at 10 Mbps baseband.

Ethernet lOBASEFL An implementation of the IEEE 802.3 standard that is designed to operate over fiber-optic cable at 10 Mbps baseband.

Ethernet lOBASET An implementation of the IEEE 802.3 standard that is designed to oper­ate over unshielded twisted -pair (UTP) cable at 10 Mbps baseband.

ETX The control character used to request the identity or status of a remote device.

ED Engineering unit [ISA-TRSO.02, Part 9­2000]; European Union; group of European countries banded together for common secu­rity and defense policies; includes the coun­tries of European Community (EC) but not to be confused with that organization. See EC.

European Workshop on Industrial Computer Systems (EWICS) The European indus­trial computer control standards group.

eutectic 1. A process by which a liquid solu­tion undergoes isothermal decomposition in order to form two homogeneous solids-one richer in solute than the original liquid, and one leaner. 2. The composition of the liquid that undergoes eutectic decomposition and possesses the lowest coherent melting point of any composition in the range in which the liquid remains single-phase. 3. The solid that results from eutectic decomposition, which consists of an intimate mixture of two phases.

eutectoid A decomposition process that has the same general characteristics as a eutectic, but takes place entirely within the solid state.

evaluation kit A small microcomputer sys­tem that is used for learning the instruction set of a given microcomputer. It usually includes light emitting diodes, a keyboard, a monitor / debugger in ROM, a small amount of RAM, and some input-output ports.

evaporated makeup Distilled water that is used to supplement returned condensate for boiler feedwater.

evaporation The change of state from a liquid to a vapor.

evaporation gauge See atmometer. evaporation rate The number of pounds of

water that are evaporated in a unit of time. evaporative cooling 1. Lowering the temper­

ature of a mass of liquid by evaporating part of it, using the latent heat of vaporization to dissipate a significant amount of heat. 2. Cooling ambient air by evaporating water into it. See vaporization cooling.

evaporator Any of several devices where a material undergoes a change of state from

liquid to gas under relatively low tempera­ture and low pressure.

evaporimeter See atmometer. even parity A data verification technique

used by "dumb" terminals in which each character must have an even number of "on" bits.

event [Cont] 1. In process control, the occur­rence of some action within a process, which can affect another process. Examples include a variable reaching some threshold of Modu­lating value, the (0inp'letion o( a sequence step, the change ofstate of a discrete switch (manually or automatically), or a point going into or coming out of alarm condition. An event is generally not connected to a time frame but serves to mark the beginning and completion of activities or conditions and to relate activities to one another. 2. An instan­taneous occurrence that is significant for scheduling the execution of an algorithm. Note: Alerts also' have algorithms that are scheduled based on events. [ISA-TRSO.02, Part 9-2000]

event-driven programming The ability of a program to respond to events rather than fol­low traditional, sequential code.

event-oriented Pertaining to a physical occurrence.

event recorder An instrument that detects and records the occurrence of specific events, often by recording on-df information against time, to show when an event starts and stops and how often it recurs.

EWMA Exponentially weighted moving average; method of SQC/SPC suited for con­tinuous process production.

Ex A designation for an explosion-protected electrical apparatus. [ISA-12.01.01-1999]

ExCA Exchangeable Card Architecture; extension to the PCMCIA specification added by Intel to ensure PCMCIA card interoperability on host systems using Intel CPUs.

Ex cable entry A cable entry that is tested separately from the apparatus enclosure but is evaluated as apparatus and which can be fitted to the apparatus enclosure during installation without further evaluation. [ISA­12.00.01-1999 (IEC 60079-0 Mod))

exception handling Those functions that deal with plant or process contingencies and other events that occur outside the normal or desired behavior of batch control. [ANSI! ISA-88.01-1995]

exception reporting An information system that reports on situations only when actual results differ from planned results. When

186

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excess air Air supplied for combustion in excess of theoretical combustion air,

Effect of Excess Air on Temperature

excess loss In a fiber-optic coupler, the opti­cal loss from that portion of light that does not emerge from the nominally operational ports of the device.

exchange A unit established by a common carrier for the purpose of administering a communications service.

excimer laser A laser in which the active medium is an "excimer" molecule-a diatomic molecule that can exist only in its excited state, The internal physics are condu­cive to high powers in short pulses, with wavelengths in the ultraviolet.

excitation 1. The external supply that is applied to a device for its proper operation, Note: It is usually expressed as a range of supply values. [ANSI/ISA-51.1-1979 (R1993)] 2. The external electrical voltage and/or current that is applied to a trans­ducer for its proper operation. Note 1: When referring to excitation in the sense of a physi­cal quantity to the measured by a transducer, use measurand. Note 2: Usually expressed as range of voltage and/or current values. Note 3: Also see excitation, maximum". [ISA-37.1­1975 (RI982)] 3. A oltage supplied by a signal conditioner to certain types of physical mea­surement transducers (bridges, for example),

excitation, maximum 1. The maximum value of the excitation voltage or current that can be applied to the transducer at room condi­tions without causing damage or perfor­mance degradation beyond specified tolerances, [ISA-37.1-1975 (RI982)] 2. The maximum allowable voltage (current) applied to the potentiometric element at room conditions while maintaining all other

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performance characteristics within their lim­its. Note: The excitation value is particularly associated with temperature. [ISA37.6-1982 (RI995)]

excitation voltage A precision voltage applied to transducers. When pressure, strain, or the like are sensed by the trans­ducer, a small portion of this voltage appears on the signal lines. The value of this signal voltage is propo.rtional to the stimulus

,.appliec;l. . ..•� exclusions See exclilsive- OR.� exclusive OR A logical operator that has the

property that if P and Q Me two statements, then the statement P*Q (where the * is the exclusive OR operator) is true if either P or Q (but not both) are true and false if P and Q are both false or both true.

exclusive-use resource A common resource that only one user can use at any given time. [ANSI/ISA-88.01-1995]

ex component A part of an electrical appara­tus for potentially explosive atmospheres. It is not intended to be used alone in such atmospheres and must receive additional evaluation and certification when it is incor­porated into electrical apparatuses or sys­tems for use in potentially explosive atmospheres. [ISA-12.00.01-19999IEC 60079­oMOD); ISA-12.01.01-1999; ISA-12.23.01­1998 (IEC 79-18 MOD)]

executable statement The constituent of a program that specifies the action of the pro­gram. It is contrasted with a nonexecutable statement, which describes the use of the program, the characteristics of the operands, editing information, statement functions, or data arrangement.

execute 1. To interpret machine instructions or higher-level statements and perform the indicated operations on the specified oper­ands. 2. In computer terminology, to run a program.

execution The process of carrying out a sequence of operations specified by an algo­rithm. Note: the sequence of operations to be executed may vary from one invocation of a function block instance to another. This vari­ance will depend on the rules specified by the function block's algorithm and the cur­rent values of the variables in the function block's data stmcture. [ISA-TR50.02, Part 9­2000]

execution of an instruction The set of ele­mentary steps that the computer carries out to produce the result specified by the opera­tion code of the instruction.

187

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execution time / expanding

execution time 1. The time required to exe­cute a program. 2. The period during which a program is being executed. 3. The time at which the execution of a program is initiated. 4. The period of time that is required for a particular machine instruction. See also instruction time.

executive 1. Short for "executive routine." See routine, executive. [ISA-ISA-RP16.4-1960-1960] 2. The controlling program or set of routines in an operating system. The executive coo~di­nates all activities in the system, including II o supervision, resource allocation, program execution, and operator communication. See also monitor.

executive Mode A central processor Mode that is characterized by the lack of memory protection and the relocation of all defined instruction codes by the normal execution.

executive program A program that controls the execution of all other programs in the computer based on established hardware and software priorities and real-time or demand requirements.

executive software That portion of the opera­tional software that controls online, response-critical events and responds to urgent situations as specified by the applica­tion program. This software is also known as the "real-time executive."

executive system An integrated collection of service routines for supervising the sequenc­ing of programs by a computer.

exfoliation corrosion A type of corrosion that proceeds parallel to the surface of a material, causing thin outer layers to be undermined and lifted by corrosion products.

exhaust 1. The discharge of working fluid from an engine cylinder or from turbine vanes after it has expanded to perform work on the piston or rotor. 2. The fluid dis­charged. 3. A duct for conducting waste gases, fumes, or odors from an enclosed space, especially the discharge duct from a steam turbine, gas turbine, internal combus­tion engine, or similar prime mover. The movement of gas may be assisted by fans.

exhaust-gas analyzer An instrument that measures the concentrations of various com­bustion products in waste gases to determine the effectiveness of combustion.

exhaust steam The steam that is discharged from a prime mover. See prime mover.

exhaust stroke The portion of the cycle in an engine, pump, or compressor that expels working fluid from the cylinder.

exhaust valve A valve in the headspace of a cylinder that opens during the exhaust

stroke to allow working fluid to pass out of the cylinder.

exit The time or place at which the control sequence ends or transfers out of a particular computer program or subroutine.

exothermic reaction A reaction that occurs with the evolution of heat. Such reactions can be difficult to control.

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Exothermic Reactor Temperature Control

exotic fuels High-energy fuels, especially the hydroborons, which have higher calorific values than the corresponding hydrocar­bons. At one time exotic fuels were proposed for use in high-performance aircraft and mis­siles.

expanded joint The pressure-tight joint that is formed by enlarging a tube end in a tube seat.

expanded memory The ability to add usable memory to a computer.

expanded metal A form of coarse screening that is made by lancing sheet metal in alter­nating rows of short slits, each offset from the adjacent rows. The sheet is then stretched in a direction transverse to the rows of slits so that each slit expands to give a roughly diamond-shaped opening.

expanded plastic A light, spongy plastics material made by introducing air or gas into solidifying plaStic to make it foamy. Also known as "foamed plastic" and "plastic foam."

expanded type In the typographical compo­sition of screen displays and printing, a type font whose width is greater than the size used for other similar elements.

Expander The tool tha t is used to expand tubes.

expanding Increasing the diameter of a ring-shaped or cylindrical part. This is usu­ally done by placing it over a circular seg­mented die and forcing the segments to

188 -_....

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move radially in a controlled manner to stretch the part circumferentially.

expansion 1. Increasing the volume of a working fluid, with a corresponding decrease in pressure and usually with an accompanying decrease in temperature, as in an engine, turbine, or other prime mover. 2. Generally, any increase in volume or dimen­sion that causes a body to occupy more phys­ical space.

expansion factor (Y) The correction for the' .. change in density befween two pres­sure-measurement stations in a constricted flow.

expansion joint The joint that permits move­ment caused by expansion without undue stress.

experience Of an employee or potential employee, a background of applicable work in design, construction, pre-operational and start-up testing activities, operation, mainte­nance, on-site activities, or technical services. Observing how others perform work in these areas is not experience. Such experience can be obtained during start-up or actual opera­tions in a nuclear facility, in fossil power plants, in other industries, or in the military. [ANSI/ISA-67.14.01-2000]

expert system 1. Software that provides a knowledge base (i.e., the symbolic represen­tation of the knowledge and reasoning of experienced human experts in a particular field) and a rule interpreter, or inference engine, to analyze problems and recommend solutions. 2. A computer program that uses stored data to reach conclusions, unlike a database which presents data unchanged.

explosion Combustion that proceeds so rap­idly that a high pressure is generated suddenly.

expansion / exposed junction

explosion door A door in a furnace or boiler setting that is designed to be opened by a predetermined gas pressure.

explosion-proof Used of an enclosure or apparatus, to describe its ability to withstand the explosion of a specified gas or vapor that may occur within it. Also entails the capacity of the enclosure to prevent the ignition of a specified gas or vapor surrounding it by sparks, flashes, or explosion of the gas or vavor within the enc.l.osure. Finally, explosion-proof also refers to the enclosure's capacity to operate at such an external temperature that . a surrounding flammable atmosphere will not be ignited. (See National Electric Code standards for definitions of explosion-proof) (See also flameproof enclosure.) [ISA-12.01.01­1999]

explosion-proof enclosure An enclosure that is capable of withstanding an explosion of a gas or v?por within it and of preventing explosive 'g~s or vapor that may surround from igniting. Such an enclosure can operate at so high an external temperature that a sur­rounding explosive gas or vapor will not be ignited. This type of enclosure is similar to a flameproof enclosure. [ISA-12.00.01-1999 (IEC 60079-0 Mod)]

explosive atmosphere A mixture with air, under atmospheric conditions, of flammable substances in the form of gas, vapor, mist, or dust. After ignition of this atmosphere, com­bustion spreads throughout the unconsumed mixture. See also ha:ardolls (classified) loca­tion. [ANSI/ISA-12.01.01-1999]

explosive gas atmosphere A mixture with air, under atmospheric conditions, of flam­mable substances in the form of gas, vapor, or mist, in which after ignition, combustion spreads throughout the unconsumed mix­ture. [ISA-12.00.01-1999 (IEC 60079-0 Mod)]

explosive test mixture A specified explosive mixture that is used to test electrical appara­tuses for potentially explosive atmospheres. [ISA-12.00.01-1999 (lEC 60079-0 Mod)]

exponent In floating-point representation, one of a pair of numerals that represent a number that indicates the power to which the base is raised. Synonymous with charac­terist ic.

exponential notation A way to express very large or small numbers in data processing.

exponentiation A mathematical operation that denotes increases in the base number by a previously selected factor.

exposed junction A form of construction of a thermocouple in which the measuring junc­tion is fully exposed to the process being

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measured. Used to provide the fastest response time if contamination is minimal.

exposure 1. For a photographic or radio­graphic emulsion, the product of the incident radiation intensity and the interval of time the radiation is allowed to impinge on the emulsion. 2. A term loosely used to indicate time of exposure in photography.

exposure time The elapsed time during which radiant energy is allowed to impinge on photographic or radiographic emulsion.

expression 1. A combination of operands and operators that a computing system can eval­uate to a distinct result. 2. Any symbol that represents a variable (or a group of symbols that represent a group of variables) that may be combined by symbols that represent oper­ators according to a set of definitions and rules. 3. In computer programming, a set of symbols that can have a specific value.

Ex Scheme An international system of certifi­ca tion for explosion-protected electrical apparatuses administered by the IECEE (lEC System for Conformity testing and Certifica­tion of Electrical Equipment) and described by IECEE-04. The eventual goal of this scheme is that a manufacturer of hazardous location electrical apparatus would be able to obtain a single 'Ex' certificate of conformity from one certification laboratory and then provide that product in any participating country without legal or technical obstacles and without the need to get it recertified locally. [ISA-12.01.01-1999]

Extended Binary Coded Decimal Interchange Code (EBCDIC) 1. An 8-bit code used pri­marily by IBM equipment that contains alpha, numeric, and control characters. 2. An 8-bit code that represents an extension of a 6-bit BCD code, which has been widely used in computers of the first and second genera­tions. EBCDIC can represent up to 256 dis­tinct characters and is the principal code used in many of current computers.

extension 1. A device for translating float motion into a useful secondary function, for indicating, alarming, transmitting or for other secondary functions. An extension usually consists of an extension tube, an extension housing, and the necessary adaptor to the pri­mary rotameter. But an extension may also be any auxiliary device fixed to the rotameter that performs specific functions. [ISA-RP16.4­1960] 2. An abbreviated code at the end of a file that tells the user what kind of informa­tion that file contains. For example, the extensions .bat, .com, .exe contain applica­

tions; .tif, .wmf, and .eps contain illustrations, and .doc and .txt contain word files.

extension bonnet A bonnet with a packing box that is extended above the usual height in order to maintain the temperature of the packing within its operating limits. [ANSI! ISA-75.05.01-2000]

extension furnace See dutch oven. extensions, controlling A controller that

derives its input from the motion of the float and <;an be inst~lled within the extension housing. (ISA~ISNRP16.4-1960-1960]

extensions, integrating An integrator that derives its input from the motion of the float and can be installed within the extension housing. [ISA-ISA-RP16.4-1960-1060]

extensions, recording The recorder is attached directly to the meter body, with the recorder pen positioned by the metering float through a magnetic coupling. [ISA-ISA­RP16.4-1960-1960j

extension spring A tightly coiled helical spring that is designed to resist a tensile force.

extensometer 1. An apparatus for studying seismic displacements by measuring the change in distance between two reference points that are separated by 20 to 30 meters or more. 2. An instrument for measuring minute elastic and plastic strains in small objects under stress, especially the strains prior to fracture in standard tensile-test spec­imens.

external communication The exchange of data between the safety instrumented system (SIS) and a variety of systems or devices that are outside the safety instrumented system. These include shared operator interfaces, maintenance j engineering interfaces, data acquisition systems, host computers, and so on etc. [ANSljISA-84.01-1996]

external graphic On the Internet, a digital graphic that must be downloaded from the Web instead of being vievved directly from a Web page. See inline graphic.

externally applied maximum voltage, Urn The maximum voltage, r.m.s., a.c., or d.c. (as specified by the manufacturer), that can be applied to the connection facilities of the apparatus without invalidating the type of the protection powder filling. [ISA­12.25.01-1998 (IEC 79-05 MOD)]

externally fired boiler A boiler in which the furnace is essentially surrounded by refrac­tory or water-cooled tubes.

externally quenched counter tube A radia­tion counter tube that is equipped with an

190

external circuit that inhibits reignition of the counting cycle by internal ionizing events.

external memory See external storage. external-mix oil burner A burner that has an

atomizer in which the liquid fuel is stmck, after it has left an orifice, by a jet of high­velocity steam or air.

external multiplexors Devices such as switching temperature indicators that permit several signals to be input on one computer input channel.

external party line (XPL) A logic level from telemetry equipment that causes the buffered data channel to switch input ports (to merge time, for example).

external sampling The rate of measurement in the digitizing process (through sampling that process) is controlled by a multiplied tachometer signal. The result is a stationary display of vibration as the speed changes. External sampling is useful for analyzing variable-speed machine.

external start (XST) The hardware-generated pulse that causes the system to start receiv­ing data (concurrent with word 1 of a frame, and often frame 1 of a subframe).

external storage 1. The storage of data on a device that is not an integral part of a com­puter but in a form prescribed for use by the computer. 2. A facility or device that is not an

'i integral part of a computer, on which data usable by a computer is stored, such as off-line magnetic tape units or punch-card devices. Synonymous with "external mem­ory" and contrasted with internal storage.

external treatment The treatment of boiler feedwater prior to its introduction into the boiler.

external trigger In vibration measurement, the beginning of each time block is controlled by an external signal. This is typically a point on the rotating system that is sensed as it passes by a fixed detector (see Keyphasor).

extract instruction An instruction that requests the formation of a new expression from the selected parts of given expressions.

extractive distillation A distillation tech­nique (employing the addition of a solvent) that is used when the boiling points of the components being separated are very close (within 3'e [SoF]) or when the components{.

"� are constant boiling mixtures. In extractive distillation, which is a combination of frac­tionation and solvent extraction, the solvent is generally added to the top of the column and recovered from the bottom prod uct by means of subsequent distillation. The cherni­

external memory / E-zines

cal added is a solvent only to the less volatile components.

extra hard temper A level of hardness and strength in nonferrous alloys and some fer­rous alloys that corresponds approximately to a cold-worked state one-third of the way from "full hard" to "extra spring temper."

e~tra spring temper A level of hardness and strength for nonferrous alloys and some fer­rous alloys that corresponds to a cold­worked state above. "f.ull hard." Beyond this level hard'ness ~nd strength cannotbe' rrie<i~ surably increased by further cold work. - ..

extreme (operating) specifications Environmental conditions that equipment qrA$,¥.stem will operate in but that may degrade their performance and/or life span. See operating speCifications and storage speCifications.

extrinsic loss In an optical fiber interconnec­tion, that portion of loss that is not intrit'lsic to the fiber but is related to imperfect joining, which may be caused by a connector or splice.

extrusion 1. A process for forming elongated metal or plastic shapes of simple to Moder­ately complex cross section by forcing duc­tile, semisoft solid material through a die orifice. 2. A length of product made by this process.

extrusion billet A slug of metal, usually heated into the forging temperature range, that is forced through a die by a ram in an extrusion process.

eyebar A metal bar that has a hole through an enlarged section at each end of the bar.

eyebolt A bolt that has a loop formed at one end in place of a head.

eyelet A small ring or barrel-shaped piece of metal that is used to reinforce a hole, espe­cially in fabric.

eyeleting Forming a lip around the rim of a hole in sheet metal.

E-zines "Electronic magazines." Generally found on the Internet, these publications are accessed via computer over some network and contain pictures, articles, sound bites, and video clips often focusing on very spe­cialized topics. Their advantage is that infor­mation can be published on line right away rather than postponed for later publication in a print edition.

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