Posted May 21st, 2018 by Harwood Engineering & filed under News.
Pressure testing equipment calibration is important in ensuring that you collect accurate and reliable data through your work. While different devices and systems will require different calibration techniques, all calibration depends on either a primary or secondary (otherwise known as “transfer”) standard. But what, exactly, is the difference between primary vs secondary standards?
To put it simply, a primary standard is a factual universal measurement while a secondary standard is a device directly calibrated previously by the primary standard.
What is a Primary Standard?
A primary standard is a standard based only on one’s knowledge of the only three fundamental units:
Mass
Length
Time
What is a Secondary Standard?
A secondary standard is any measuring device that has been calibrated against a primary standard.
In pressure work, the error band on the primary standard is generally so many percent of reading – the error is the summation of the uncertainty in the weight measurement plus the uncertainty of the piston measurement; secondary devices are usually reported as +/- a percent of full scale. For most production work, that is sufficient. However, if the device being calibrated is, itself, going to be used as a standard to calibrate others, it should have a primary calibration.
Harwood Engineering has been providing high pressure testing services more than 65 years. Contact us today with any questions you may have about primary vs secondary standards or your pressure testing needs.
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