Calibration is a verification process on the accuracy of measuring equipment by given reference standards. The reference standard is a device ,..vith the measurements is known or assigned correctness. The measuring equipment is the unit under test. test instrument. or any of several other names forte device being calibrated. Two metrological concepts with direct linkage to calibration are the measurement traceability and measurement uncertainty.

Measurement results are considered valid only if they are linked to establishing national or international measurement standards. and this linkage is called the measurement traceability. ,vi ich is to ensure the results is valid.