Characteristics of Measurement

Table of Contents

The instrument used for measurement should have static and dynamic characteristics as mentioned below.


Accuracy is the difference between the instrument’s reading and its actual values ​​that are measured. Accuracy is expressed as a percentage of the top scale value regardless of where the scale reading is taken. Let us assume that the range of a device is 0-100 units. If you are applying 50 units and the meter is reading 49 units, the error is -1 units. Similarly if the meter reading is 51 then the error is +1 unit. Therefore the error can be + or – if the accuracy of an instrument is specified as 1%, this means that the meter can read more or less 1 unit per range.


The repeatability of an instrument means that the instrument will read the same reading on the scale regardless of how the point of measurement is reached. It means fast or slow, upscale or downscale. If the instrument is reading 49 on the upscale scale instead of 50 it should read the same on the downscale reading. If it is reading 51 units then the error is called hysteresis, which is due to frictional losses.


The sensitivity of an instrument is the ability to respond to a small change in the value being measured. This is the smallest change that will cause the effective motion of the measuring element. The sensitivity must be several times higher than the accuracy and is largely determined by friction and other damages on the moving mechanical parts of the equipment.


The ability to read an instrument without a change in accuracy for performance days, weeks and months, is important. Performance means that the equipment must be made of a material that will not corrode, that will show slightly worse, and that will not alter physical characteristics.

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