Various Static Characteristics

1. Accuracy :-

It is a degree of Closeness with which the reading on the instrument approaches to the true value of the quantity to be measured.

eg. :- Suppose you have a conductor which diameter is of 3.325 mm exactly. now when you measure it by a micrometer whose least count is of 10 micro meter or a 0.01 mm, then you may get the reading as 3.32 mm which is somewhat correct, but not accurate. so to measure it you need a micrometer whose least count should be 1 micro meter(0.001 mm) or a 5 micro meter(0.005 mm ) then you can get more accurate readings.

2.Sensitivity:-

Sensitivity is defined as a response of the instrument to the smallest change in the input variable.

It is also defined as a ratio of change in the output of an instrument to the change in the value of the quantity to be measured.

mathematically :-

Sensitivity :- change in Output / change in input.

eg. :- suppose you have a thermocouple which can measure a temperature from 0 degree Celsius to 45 degree Celsius, and which can give a maximum output reading as 5 volt for maximum input variation.

so the sensitivity of the instrument is now :-

maximum output variation / maximum input variation.

= 5/45 = 0.11 volt/degree Celsius.

3. Precision:-

The Precision is refereed as the closeness of the measurement to each other. or it is defined as the quantity, condition or fact of being exact.

You may define the precision as the degree to which the repeated measurements under the unchanged condition shows the same results.

Note :-  A measurement system cant be accurate and precise at the same time. 

eg :- suppose you are checking the voltage of a battery and taken the readings are like 12.15V, 12.18V, 12.14V,12.16V, 12.17V, 12.16V.

now you can see the readings on voltmeter are not same but nearly close to each other. so we can say the readings are precise.

4. linearity:-

Linearity is nothing but the consistency of the accuracy over full range of measurements.

eg:-Suppose you are getting the same change in output measurement for every change in the input quantity then it is called linearity of instrument.

This property of instrument is very very useful in the scientific work.

5. Reproducibility:-

Reproducibility of the system or the instrument is its ability to produce same output if the same input is given to it.

Note :- The Reproducibility does not focus on the, Location of measurement, Surrounding climatic conditions, and the person who is taking measurement.

6. Repeatability :-

Repeatability is defined as the variation in the repeated measurement over a same subject under the same identical conditions over a short period of time.

Note :-  In this characteristic, measurement are taken - on same measurement location, same place, same measurement procedure, same observer, same measurement instrument, and measurement repetition are taken over a short period of time.

7. Resolution:-

Ability of the measurement system to detect and faithfully indicate small changes in the characteristics of the measurement results.

8. Threshold :-

Threshold is the amount of measurement change required before a measurement instrument react to a change in measurement output or produce a specific result.

Note :- 

Resolution :- it is a minimum change in input quantity measured by instrument.

threshold :- it is a minimum input measured by an instrument.

9. Drift:-

Drift is a gradual shift in the indication or record of the instrument over an extended period of time, during which the true value of the variable does not change.

Drift is a undesirable quantity in the instrument.

10. Stability :-

It is the ability of the instrument to maintain a certain physical property at a constant value, while rejecting any disturbances in the environment.

11. Tolerance :-

Tolerance refers to the total allowable error with in the instrument for a input.

12. range or span of the instrument:-

Span or the range of the instrument is defined as the algebraic difference between the lower and upper range values of instrument.