EC2351- MEASUREMENTS AND INSTRUMENTATION
TWO MARKS QUESTIONS AND ANSWERS
UNIT I
BASIC MEASUREMENT CONCEPTS
1. Define – Measurement ( May / June 2013)
The measurement of a given quantity is essentially an act or the result of comparison between the
quantity (whose magnitude is unknown)...
EC2351 MEASUREMENTS AND INSTRUMENTATION VI SEM ECE
EC2351- MEASUREMENTS AND INSTRUMENTATION
TWO MARKS QUESTIONS AND ANSWERS
UNIT I
BASIC MEASUREMENT CONCEPTS
1. Define – Measurement ( May / June 2013)
The measurement of a given quantity is essentially an act or the result of comparison between the
quantity (whose magnitude is unknown) and predefined standard.
2. Mention the basic requirements of measurement.
The two basic requirements of measurement are
The standard used for comparison purposes must be accurately defined and should be
commonly accepted.
The apparatus used and the method adopted must be provable.
3. How are the methods of measure ment classified? (May/Jun 2013)
The two methods of measurement may be broadly classified into two categories:
Direct method
Indirect method.
4. Write the two major functions that can be performe d by all branches of engineering.
Design of equipment and process
Proper operation and maintenance of equipment and process.
5. What is meant by direct method of measure ment? (Nov/Dec 2012)
In direct method of measurement, the unknown quantity is directly compared against the
standard. The result is expressed as a numerical number. The standard, in fact is a
physical embodiment of a unit.
6. What is meant by indirect method of measure ment? (Nov/Dec 2012)
Prepared by A.DEVASENA., ASSOCIATE PROFESSOR/ECE Page 1
,EC2351 MEASUREMENTS AND INSTRUMENTATION VI SEM ECE
Measurement by direct methods is not always possible, feasible and practicable. These
methods in most of the cases are inaccurate because they involve human factors. They are
also less sensitive. Hence direct methods are not preferred and are rarely used. We are often
using indirect methods for measurement purposes.
7. Define − Measurement (May/Jun 2013)
Measurement is an act or the result of comparison between an unknown quantity
and a predefined standard.
8. Define – Instrume nt ( May / June 2012)
It is defined as a device for determining the value or magnitude of quantity or variable.
9. List out the types of instruments.
The three types of instruments are
Mechanical instruments
Electrical instruments
Electronic instruments.
10. Give the classification of instruments.
There are many ways in which instruments can be classified. Broadly instruments are
classified into two categories. They are
Absolute instruments
Secondary instruments.
11. What are absolute instrume nts?
Absolute instruments give the magnitude of the quantity under measurement in terms of
physical constants of the instrument. The examples of this class of instruments are, tangent
galvanometer and Rayleigh’s current balance.
12. What are secondary instruments?
These instruments are so constructed that the quality being measured can only be
measured by observing the output indicated by the instrument. These instruments are
Prepared by A.DEVASENA., ASSOCIATE PROFESSOR/ECE Page 2
,EC2351 MEASUREMENTS AND INSTRUMENTATION VI SEM ECE
calibrated by comparison with an absolute instrument or another secondary instrument which
has already bee n calibrated against an absolute instrument.
13. What are the two modes of operation of secondary instruments?
The two modes of operation of secondary instruments are:
Analog mode and
Digital mode.
14. How are the instrume nts classified based on the results presented by the m?
Instruments can be classified into two categories as deflection and null types depending
upon the way they present the results of measurements.
15. What is meant by null type instrume nt?
In a null type instrument, a zero or null indication leads to determination of the
magnitude of measured quantity. The null condition is dependent on some other known
conditions.
16. What are the various functional elements of measure ment systems?(May/June 2012)
The various functional elements of measurement systems are
(i) Primary sensing element
(ii) Variable conversion element
(iii) Variable manipulation element
(iv) Data transmission element
(v) Data presentation element.
17. What is the function of the data presentation element in an instrumentation system?
When the elements of instruments are physically separated, it becomes necessary
to transmit data from one to another. This function is performed by the data presentation
stage.
18. List out the characteristics of the measure ment system.
Prepared by A.DEVASENA., ASSOCIATE PROFESSOR/ECE Page 3
, EC2351 MEASUREMENTS AND INSTRUMENTATION VI SEM ECE
The characteristics of the measurement system can be divided into two types. They are
Static characteristics
Dynamic characteristics.
19. Give the function of variable manipulation element.
The function of variable manipulation element is to manipulate the signal presented to it
preserving the original nature of the signal.
20. Compare null type and deflection type instruments.
Null type instruments are more accurate than deflection type instruments.
Null type instruments can be highly sensitive as compared with deflection type
instruments.
21. Mention the applications of measurement systems.
The applications of measurement systems are
Monitoring of processes and operations
Experimental engineering processes.
22. List out the functions pe rformed by instruments.
Three main functions are performed by the instruments. They are
Indicating function
Recording function
Controlling function
23. What is meant by signal conditioning?
Prepared by A.DEVASENA., ASSOCIATE PROFESSOR/ECE Page 4
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