At Transcat, we believe in calibrating items properly, and in documenting our calibrations as accurately as possible. We are also passionate about metrology in general, and we occasionally get a chance to review competitive calibration certificates. While reviewing, certs may sound like as much fun as having a root canal, this is what we do and, believe it or not, we’re glad to do it. Really!
Most often, the certs we review are done well. Sometimes, though, we find examples of calibration results that seem to make no sense whatsoever. This is one such example. Below, you will find the actual cert (we removed the item, competitor and customer information) and what Transcat's experts have determined about the individual results.
In this case, there are almost too many inconsistencies to list. Perhaps it will help you to think of it as a “Where’s Waldo” game. Have fun!
Transcat has designed a tool that allows you to visualize risk. It works on the basis of False Accept and False Reject decisions. It also quantifies any risk that is present so that you can create decision rules to handle the amount of acceptable risk in your measurement processes. However, when a calibration service provider (CSP) applies the wrong tolerances to your instrument calibration, this risk tool cannot help you until the correct tolerances are applied.
In the example shown in the figures, the actual values from the 3458A calibration were used. This calibration was reported to be a full calibration to manufacturer’s specifications.
As an example of what wrong tolerances can mean, here are the results of the AC Voltage test for 10V @ 100 kHz: