And now, let us define Verification.
As per JCGM 200:2012,” verification is the provision of objective evidence that a given item fulfills specified requirements”
Verification includes fulfillment of specified requirements, it means a check to confirm if a given measured value (DUT output) is within the specified requirements we set or follow. The specified requirements I am referring to is the ‘acceptance criteria, the ‘tolerance limit’ or the Maximum Permissible Error (MPE). There are other requirements but this is what we always focus on for measurement results.
verification of a pressure gauge using its accuracy class as the basis for a ‘tolerance limit’ to determine a ‘pass’ or ‘fail’ results where the ‘error’ is taken from calibration results.
Our main goal here is to determine if the DUT fulfills the specified requirements and if the output display is within (or outside) the required specifications.
“While calibration is the comparison of DUT reading with the Reference Value, Verification is the confirmation of the DUT reading if it is within the range of the “Tolerance Limit”.
Once we confirm that the output of the DUT is within its tolerance limit, a ‘Pass’ or ‘Fail’ decision is made. This is where a ‘decision rule’ is also implemented.
This is why verification gives more meaning to the result of calibration.
A simple verification process includes:
Using a traceable reference standard to get the output reading of the DUT. The result is the measured value based on a verification procedure.
Set the tolerance limit or MPE.
Check if the measured value is inside the tolerance limit.
Then based on the result, decide if it is a Pass or a Fail.
Record in a verification report and determine disposition.
Take note that the process of gathering data for verification is the same as calibration. We are still using a reference standard, which means we have an expected value that is from a reference standard before we take the reading of the DUT- a comparison stage.
It is important to use a calibrated and traceable check standard. This is because we cannot ensure the confidence of our verification result if the accuracy of our check standard is questionable
But there are times when the reference standard or check standard used for verification is not necessarily calibrated regularly as long as it is properly controlled and used only for the purpose of verification.
Another important requirement for verification is the tolerance limit, we should know first the tolerance limit before performing verification.
The tolerance limit can be based on ‘acceptance criteria’, Maximum Permissible Error (MPE), or ‘accuracy’, which mostly comes from manufacturer specifications.
During verification, we need the measurement results from the calibration we performed, specifically the “error” and “uncertainty” values.
