Characteristics of Measurement

Characteristics of Measurement

Essentially the instruments used for measurement have  characteristics such as accuracy, repeatability, sensitivity, display.


Basically, accuracy is defined as the difference between the instrument's reading and its actual reading or measured value. and is expressed as a percentage of the top scale value regardless of where the scale reading is taken.


The repeatability of an instrument means that the instrument will give the same reading on the scale regardless of how the measurement point is reached. It means fast or slow, high or low. If the instrument reads 49 instead of 50 on the upper scale, it should read the same on the downscale reading. If it reads 51 units, the error is called hysteresis, which is caused by frictional losses.


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


The ability to read the instrument for days, weeks and months of performance without a change in accuracy is critical. Functionality means that the equipment must be made of materials that will not corrode, that will show little worse, and that will not change the physical characteristics.