Inspec Insights

7 Key Differences Between NIST and ISO Certification

NIST Traceable (National Institute of Standards and Technology) – a NIST certification means that a product has been tested against NIST’s Standard Reference Materials (SRMs) and meets the organization’s exact specifications. 

The measurement is made using a standard reference artifact (in most cases a gage block) that NIST has certified to be a specific size.  Theoretically, this provides for an unbroken chain of measurement reference all the way back to a primary national standard.  It does not, however, consider how that measurement is made.  This gives rise to several questions:

  1. Is the measurement made in a controlled environment, where temperature and humidity are tightly controlled within the tolerances required to make accurate measurements?
  2. Have both the standard reference artifact and the product being measured been allowed to equilibrate in the measurement environment to ensure that both are stable at the time of measurement?
  3. Is there a procedure for making the measurements?
  4. Has the procedure been demonstrated to be repeatable in an R&R study?
  5. Is the technician performing the measurement trained to operate the equipment properly?
  6. Is the technician periodically tested to demonstrate continuing proficiency?
  7. Is it possible to contact the company that supplied the traceable certificate to obtain a more detailed report certifying that the measurement is accurate?

VS.

ISO Certified (International Standards Organization) - ISO 17025 certification means not only that it has been tested against NIST’s (in the US, or other countries Standards Institutes) SRM through an unbroken chain of calibrations, but also that the technician is qualified to perform this calibration using an accepted method of calibration and is monitored by an effective Quality Management System, and indicates the equipment used to perform this calibration (the equipment also having been calibrated through an unbroken chain to the SRMs).

This measurement is also made using a gage block or other standard reference artifact however, the measurement takes place in an ISO 17025 accredited calibration laboratory.  In addition, that laboratory is periodically audited by an ISO 17025 accrediting body to ensure all ISO 17025 requirements are being met.  ISO 17025 requires that all calibration laboratories adhere to the following:

  1. Measurement is made in a controlled environment, where temperature and humidity are tightly controlled within the tolerances required to make accurate measurements.
  2. Both the standard reference artifact and the product being measured are allowed to equilibrate in the measurement environment to ensure that both are stable at the time of measurement.
  3. There is a written procedure for making the measurements.
  4. The procedure has been demonstrated to be repeatable in an R&R study.
  5. The technician performing the measurement is trained to operate the equipment properly.
  6. The technician is periodically tested to demonstrate continuing proficiency.
  7. The accredited calibration laboratory supplies a traceable certificate, with detailed report, certifying that the measurement is accurate.

All ISO certificates of calibration adhere to ISO 17025:2005 standards, including: trace numbers, date of calibration, CMC data (Calibration Measurement Capability) and certified inspector signature. 

ISO 17025 Certifications are generally more expensive, but it is because of all the additional requirements to provide the confidence of results as indicated above.

Now that you understand the difference between the NIST and ISO you can decide what is best for your situation.  If you have questions regarding the type of calibration certificate your company requires, they can best be answered by your internal ISO auditor or talking with us here at Inspec.

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