Calibration certificates can be confusing, especially if you aren’t familiar with metrology. The calibration certificate documents the quality and accuracy of the measurement device, so it’s important to understand the terminology and what the random numbers mean to you.
The document includes various information about the device, as well as the details about the calibration laboratory and the standards they adhere to. One particularly critical piece of information to pay attention to is the “uncertainty” of the calibration performed, a value required for ISO 17025 standard.
Simply put, the number associated with the “uncertainty” indicates how reliable the measurement is. Every measurement comes with some uncertainty, or doubt, due to a variety of factors including the tools used, the person performing the calibration, and the method used. This number is an indicator as to whether or not this measurement is appropriate for use.
It’s important to keep in mind that “error” is not the same as “uncertainty” and has no meaning without the “uncertainty” of the measurement. Error is the difference between the reference standard and the “uncertainty” of the measurement.
Using a MadgeTech calibration certificate as an example, 0.039 number is the uncertainty of the calibration measurement performed.
For the statement “expressed at 95% confidence level using coverage factor k=2”, this is how MadgeTech reports its uncertainty. The statement of uncertainty is reported with a coverage factor of k=2, which indicates approximate 95% confidence. This means that if you were to make 100 measurements, you could be confident that (at least) 95 of them would be accurate within the stated uncertainty.
MadgeTech offers a scope of calibration services at its in-house ISO/IEC 17025 accredited laboratory. For more information on standard and custom calibrations, call us at (603) 456-2011 or email [email protected].