All manufacturing companies that get audited require some or all of their calibration certificates to specify the calibration uncertainty. At a minimum, some manufacturers only need certified uncertainty for gauges that are reference standards used to calibrate other gauges. Those companies usually send their reference standards to an outside calibration source for certification, but it would be convenient to know how to certify your own gauges.

For example, you might need to calibrate some pin gauges, but perhaps you don’t have a certified micrometer because you don’t send micrometers out. For those companies, as well as companies that must certify all of their calibrations, this article will use popular software to show what steps are required to do your own uncertainty certifications.

Basics: the bias study

The first step is to measure repeatability on a reference standard and calculate the difference between the average measurement and the reference value. This difference is called “bias,” and therefore the study is usually called a “bias study.” Sometimes, you may see it referred to as a “repeatability study” or a “type 1 study.”

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