I wanted to make a post to give general guidance on whether or not you should pursue measurement devices that have NIST (National Institute of Standards and Technology) traceable data. I also want to cover some misconceptions or frequently asked questions that NIST has come across.
We get a lot of questions regarding if certain tools, sensors, measurement devices or equipment, and more have some kind of calibration certificate or not. Most of the time, it is in the context of NIST traceable data. Here are some frequently asked questions that might be able to give you some insight for evaluating if it is required.
Most Common Misconceptions Observed
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“The devices have traceability themselves.”
NIST informed me that traceability is actually on measurement results, not the product or instrument. -
“Calibration is directly tested by one lab.”
This is not accurate. Many NIST calibration customers are secondary calibration labs. These labs may send in a “standard volt” reference to NIST and have them calibrate it. If they are
accredited for those measurements, then it can be said that it is traceable through NIST. There is supposed to be a traceability chain. -
“Calibration certificates must exist if components in a device are traceable to a NIST standard.”
It is feasible that some sensors or components in devices could have measurements traceable to NIST.However, the manufacturer cannot claim traceability through NIST or other institutes unless they are accredited to do that measurement.
I am re-iterating the same point because this is a crucial detail.
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“Calibration results in the certificates mean they are fit for purpose.”
According to NIST, “not necessarily or automatically because traceability imposes no restrictions on the size of uncertainty associated with a measured value.” There isn’t a guarantee that the “measurement uncertainty is adequate for a given purpose or that there is an absence of mistakes.”
NIST Resources
There are contacts available on the NIST site if you have more questions. You can also refer to these two resources they provided that are quite helpful:
NIST Customers have to go through an incredibly detailed checklist mentioned in the FAQ above. This may be a large factor why calibration certificates aren’t common, readily available, and generally expensive to a manufacturer.
TechForum Resources
Here are more useful links that should help you in your decision process.
- General Details on Calibration Certificates
- Guide on What Does and Doesn’t Require Calibration
- Difference Between NIST and Factory Calibration
- Calibration Certificates Must Be Requested Before an Order
Last Notes
If a datasheet explicitly calls out that a calibration certificate comes with and it didn’t arrive, please let us know. Generally speaking, if a datasheet does not include a specific, orderable part number that explicitly calls out a calibration certificate, then it is very unlikely they have the same device available with said documentation. It is possible that they may have some kind of manufacturer defined calibration process, but manufacturers do not generally share this with distributors. A datasheet is supposed to define tolerances, input/output parameters, and conditions for sensors or devices. It may be best to consider this as a “calibration” document in lieu of a certificate.
Lastly, if orderable part numbers are stated in the datasheet, there is usually going to be lengthy lead times and potentially high minimum order quantities. These aren’t considered standard parts by the manufacturer.