errror nithya2

Session 2

Session Name: Errors in Measurement System

Author Name: Nithya V.

Department: Electronics and Communication

Engineering

Subject/Course: Measurements and

Instrumentation

Ver:1.0 Errors in Measurement System Nithya V., MAM College of Engineering

Session Objectives At the end of this session, the learner will be able to:

Define Measurement.

Define errors in measurements.

Write the classification of errors.

Illustrate the different types of errors.

Teaching Learning Material

Black Board and Chalk

Errors in Measurement System Page 3 Nithya V., MAM College of Engineering

Session Plan

Time (in min)

Content Learning Aid

and Methodology

Faculty Approach Typical Student Activity

Learning Outcomes (Blooms + Gardeners)

10 Recap: Instruments and its Classification

Rapid-fire Questions

Conducts

Participates Recalls Answers Listens

Remembering Interpersonal Intrapersonal Verbal

05 Introduction to Measurement

Learning from Example

Facilitates Introduces

Answers Relates

Analyzing Intrapersonal Logical Verbal-Linguistic

10 Errors in Measurement and its Classification

Chalk and Talk Explains Listens

Remembering Intrapersonal Linguistic

25 Different Types of Errors

Brainstorming Chalk and Talk

Facilitates Explains

Listens Participates Discusses Identifies

Analyzing Intrapersonal Interpersonal Logical Verbal-Linguistic

10 Conclusion Buzzer Round

Conducts Guides Encourages

Participates Recalls

Analyzing Interpersonal Logical Verbal-Linguistic


Session Inputs

Recap: Instruments and its Classification

We shall begin the session by asking questions on the topic which

was taken in the previous session- Instruments and its

classification.

Suggested Activity: Rapid-fire Questions

We can select six learners and form three teams of two learners each. To

each team, 5 or 6 questions can be asked. The answers should be given

quickly.

Sample questions:

What is an instrument?

Name any two types of instrument.

What is the advantage of digital instruments?

Give an example for deflection instrument and null instrument.

Give an example for absolute instrument.

An instrument is a device used to measure an unknown variable

or quantity.

Classification of instrument:

Absolute and secondary instruments

Analog and digital instruments

Advantage of digital instruments: high accuracy, high speed,

elimination of human errors.

Example for deflection type instrument: Permanent moving coil

ammeter.

Example for null type instrument: DC potentiometer.

Example for absolute instruments: Tangent Galvanometer.


Introduction to Measurement

The term measurement can be introduced with the help of an

analogy.

Suggested Activity: Learning from Example

Facilitator: If fever strikes a human body, how will you find out?

Learners: Using thermometer.

Facilitator: How will you confirm fever using a thermometer?

Learners: If the temperature of human body is above 98.6 degree

Fahrenheit, then we can conclude that the body is suffering from fever.

Facilitator: Yes We compare the measured variable with the threshold value. If the measured temperature is higher than the normal human body

temperature, then we conclude that the person has fever. By using this analogy we can define measurement.

By relating the above said analogy, we can define measurement

as the act, or the result of a quantitative comparison between a

predetermined standard and an unknown magnitude.

Errors in Measurement and its Classification

After introducing the concept of measurement, we can discuss

the errors in measurement and its classification.

Errors:

Errors and uncertainties are inherent in the process of making any

measurement and in the instruments with which the

measurements are made.

The study of error is important as a step in finding ways of

reducing them, and also as means of estimating the reliability of


final results.

Classification of errors:

Gross Errors

Systematic Errors

Instrumental Errors

Environmental Error

Observational Error

Random Errors

Different Types of Errors

Having seen the classification of errors, the different types of errors

can now be explained with the help of an activity.

Suggested Activity: Brainstorming

1. We can divide the learners into five groups, give a clue or hint about

each type of error and give each group 10 minutes time to discuss

about the different types of error. The learner has to say what that error

is and how it occurs.

2. After the allotted time, responses from the learners of each group can

be listed on the board by the facilitator. (This should be repeated for

each type of error.)

3. After listing the responses on the board, we can remove the irrelevant

responses after providing appropriate explanation.

4. Finally, we can consolidate the remaining responses, add the missing

points and provide the correct explanation.

Samples:

Facilitator my give a clue for gross error as error due to people like us.

Responses from learners: human errors; noticed the readings wrongly; we

will see one reading in an instrument, but while writing we will write some

other reading; due to carelessness, etc.


Gross Errors: These errors occur due to human mistakes in reading

instruments and recording and calculating results of

measurement. Although it is probably impossible to eliminate the

gross error completely, yet one should try to anticipate and

correct them. The mathematical analysis of gross errors is

impossible since these may occur in different amounts. While

some gross errors may be easily detected, others may go

unnoticed.

Systematic Errors: The systematic errors are repeated consistently

with the repetition of the experiment and are caused by such

effects as Sensitivity Shift, Zero-offset and known non-linearity.

Instrumental Errors: These errors arise due to

Inherent short comings of the instruments.

Misuse of the instruments.

Loading effects of the instruments.

Environmental Errors: These errors are due to conditions

external to the measuring device (e.g. effects of

pressure, temperature, humidity, dust, vibrations, external

magnetic or electrostatic fields, etc.).

Observational Errors: These errors are due to carelessness

of operators. Even when an instrument is properly

selected, carefully installed and faithfully calibrated,

shortcomings in the measurement occurs due to certain

failings on the part of the observer.

Random Errors: The random errors are accidental, small and

independent. They vary in an unpredictable manner. The

magnitude and direction of these errors cannot be predicted

from knowledge of measurement system; however these errors

are assumed to follow the law of probabilities.

Conclusion

We can conclude this session by asking questions to the learners

on the topics covered.


Suggested Activity: Buzzer Round

Divide the learners into groups of five each. Start the quiz by asking a

question to group1. Group1 has to answer the question and ask a question

to group2. The question asked by group1 should be related to the answer

given by them. Group2 has to answer this question and ask another

question to Group3 based on their answer and so on. The scores for correct

answers can be written on the board by the facilitator.

Sample Questions:

1. What is measurement?

2. Define errors in measurement system.

3. What are the types of errors?

and so on


Summary

In this session, we learnt to:

Define Measurement.

Define errors in measurements.

Write the classification of errors.

Illustrate the different types of errors.


Assignment

1. Discuss how errors in measurement can be minimized.

2. Identify the different sources of errors.


References

Albert.D.Helfrick, William.D.Cooper, Modern Electronic Instrumentation and Measurement Techniques.

R.K. Rajjput, Electronic Measurements and Instrumentaion.

Documents

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