Learning program: Mechanic – electrician

Name of the program: II. class Numerical systems Analog and numerical representation of

quantities

Made by: Mgr. Holman Pavel

Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002

je spolufinancován Evropským sociálním fondem a státním rozpočtem

České republiky.

To start with, I’d like to compare analog and numerical method.

If we should choose from analog (analogue) measuring device or digital measuring device, which one shall we choose?

We choose the digital one because of its undisputable advantages. If we measure for example the electric current, the pointer of the analog ammeter is proportionate to the measured voltage.

If we want to measure the result, we have to compare the position of the pointer with the scale.

The scale is divided into segments, which correspond to the certain part of the device degree. One segment corresponds to the certain value (f.e. 1 segment = 100 mA).

That’s why we have to guess the real value of the measured quantity.

If someone else measures the same figure, he may guess a different value on the scale.But if we measure the electrical current by a numerical ammeter, the current value figure is determined by the group of numbers on the digital device display.

The projection is then clear and everybody will have the same results. Another advantage of numerical devices could be an automatic setting of the best working scope and the correct projection of the measured quantity sign.

We can conclude that the numerical projection of the measured quantity is more accurate.Compared to that, the analog figure is perceived and assessed often faster. For example a time figure on the analog wrist watch can be often evaluated easier than the figure on the watch with the numerical display.

Analog quantities are continuous functions of time (f.e. voltage).It means that each analog quantity can have in any interval indefinite number of values. The signal is due to the material imperfection and the external environment distorted or degraded during its processing. Most important thing is that the value isn’t changing rapidly and has a definitive value in each moment.

Analog quantities are measured and processed via analog circuits. Analog quantities (voltage, electrical current) can be measured by numerical devices.

An analog signal has to be transferred to the numerical signal, which is then further processed.

Measured physical quantities, which can be found all around us, are almost always analog (temperature, pressure, voltage, current).

Circuits processing signals can be divided into two basic groups:1. Analog circuits2. Numerical circuits

Analog circuits - process signals, which are functions of time and are continuous in time, meaning that they are changing continuously. They are for example sound waves, light radiation, the temperature of the environment or previously mentioned voltage signal as a function of time, which is also analog.

Continuous analog signal

2. Numerical circuits- process most often double-value signals. These signals are called binary or logical.

A binary signal is determined by the combination of a number of bits so high to represent an analog signal with the adequate accuracy by a numerical signal.

The picture depicts the example of the binary signal by using four bits. We can see, that there is a definite number of levels represented by a group of nulls and ones for voltage values depiction.

Example of the numerical level signal

According to the quantity measured by measuring devices, we distinguish:

Voltmeters – measure voltage,Ammeters – measure electrical current,Ohmmeters – measure electrical resistance,Wattmeters – measure electrical power,Electricity meters – measure electrical work (energy) of the electric current,Oscilometers– measure frequency of the electric current,Phasemeters – measure (cos Φ),Galvanometers – measure very low electric currents, voltage and charges.

According to the measuring method we distinguish devices to measure:

One electrical quantity in stable stage (f.e. current, voltage, …),

An addition and a subtraction of electrical quantities (f.e. tree-phase electric meter, variance voltmeter, …)

Electric quantities product (f.e. wattmeter),

Electric quantities quotient ( f.e. ohmmeter),

Electric quantities time integral (f.e. electric meter).

galvanometr

According to the device use we distinguish:

Distributor devices – permanently attached in distributors, switching stations or in control rooms. They serve as constant measuring devices.Portable devices (assembly) – used for the workshop measuring, often constructed as universal (measure more quantities).Laboratory devices – used for the accurate measuring in laboratories and testing rooms.Standards – are the most accurate devices used for laboratory results verification.

According to the measuring device apparatus we distinguish:Magnetic-electricFerromagneticElectrodynamic and ferrodynamicInductiveElectrostaticThermicVibrational

According to the pointer type we distinguish:Analog – divergence is showed by the pointer – most commonWith the light trace – there is a light ray on the scale, which is rebound from the mirror located on the revolving device Recording (registration) – the divergence is graphically recorded by the liner on the paper stripVibratory – the divergence is realized by the oscillation of steel needles

Question for 1 000 Kč

Which device measures voltage?

a) Ammeter

b) Ohmmeter

c) Voltmeter

d) Phasemeter

Question for 2 000 Kč

What is the basic unit of electric current?

a) Ampere

b) Ohm

c) Volt

d) Watt

Question for 3 000 Kč

While processing which signal outer environment conditions cause distortion or other signal degradation?

a) Numerical

b) Binary

c) Digital

d) Analog

Question for 5000 Kč

Numerical circuits most often process signals:

a) Decimal

b) Analog

c) Binary

d) Sexagesimal

Question for 10 000 Kč

Convert: 100 mA = ??? A

a) 1,0 A

b) 0,1 A

c) 10 A

d) 0,01 A

Question for 20 000 Kč

Which measuring devices are being used for constant measuring?

a) Standards

b) Distributor

c) Laboratory

d) Portable

Question for 50 000 Kč

Quotient of electric quantities is measured by:a) Voltmeter

b) Ohmmeter

c) Wattmeter

d) Ammeter

Question for 100 000 Kč

Measured electrical quantities occurring in our surroundings are:

a) Analog

b) Numerical

c) Digital

d) Logic

Question for 200 000 Kč

Which measuring devices are the most accurate?

a) Standards

b) Distributor

c) Laboratory

d) Portable

Question for 500 000 Kč

Which measuring devices measure very low current, voltage and charges?

a) Wattmeters

b) Phasemeters

c) Galvanometers

d) Oscilometers

Question for 1 000 000 Kč

Which analog measuring devices have the divergence recorded by the liner on the paper strip?

a) Analog

b) With the light trace

c) Recording

d) Vibratory

End of the game

Sorry your answer is wrong.

Mužík, J. Management ve vzdělávání dospělých. Praha: EUROLEX BOHEMIA, 2000. ISBN 80-7361-269-7.

Operační program Vzdělávání pro konkurenceschopnost, ESF 2007 – 2013. Dostupné na: http://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro-

konkurenceschopnost ANTOŠOVÁ,M., DAVÍDEK. V. Císlicová technika.Ceské Budejovice: KOPP, 2004. ISBN 80-7232-206-0. JANSEN, H., ROTTER, A. A KOL. Informacní a telekomunikacní technika. Praha: EUROPA- SOBOTÁLES cz.,2004. ISBN 80-86706-08-7. Pecina, J. Ing. PaedDr. CSc.; Pecina, P. Mgr. Ph.d. Základy císlicové techniky. Brno: