Calibration is the comparison of two measurement devices or system, one is the reference standard and the other is the unit under calibration. Instrument calibration is intended to eliminate or reduce bias in an instrument’s readings over the range for all continuous values. For this purpose, reference standards with known values for selected points covering the range of interest are measured with the instrument in question. Then a functional relationship is established between the values of the standards and the corresponding measurements. This process which involves the verification of the operational integrity of instruments is to be carried out periodically in-house under controlled conduction or onsite.
Traceability
The standards used in calibration has to be calibrated with another reference standard of better accuracies. This process goes up as a chain – called the Traceability Chain, up to the highest level of standards, maintained by a National Laboratory. Thus Traceability means that there is a documented link between the accuracy of an instrument and the National Standards. In India all primary standard are maintained by National Physical Laboratory (NPL), New Delhi.
