CALIBRATION STUDY

  

CALIBRATION STUDIES   

Chapter 8

Accuracy

Bias :

            Bias is the difference between the observed average of the measurement and the true value.

True value is measured from an instrument with higher precision.

Note :
Bias ( or error ) is mentioned in the instrument calibration report.

Bias,  Linearity and stability are under calibration study.
Repeatability and Reproducibility are under Gauge R & R study.

Linearity :

" Linearity is the difference in Bias value over the expected operating range of the measurement gauge".
 eg. Vernier Calliper
" Linearity is a measure of any change in Accuracy and Precision over the range of Instrument Capability "

Stability :

Stability is the variation ( differences ) in the average over extended periods of time using the same gauge and appraiser to repeatedly measure the same part.

Note : True value is theoretically correct value.It is measured by a Instrument with very high precision and high accuracy by a perfect operator.

Discrimination :

Discrimination is fineness of scale divisions of an instrument.

If , finest division = 0.001"
Discrimination = 0.001"

Discrimination is not the same as accuracy or repeatability but is an indication of smallest unit of measure on the scale.

Discrimination is also called Resolution.