The relationship between ISO 17025 vs. ANSI Z540-1



I am confused as to the relationship between ISO 17025 and ANSI Z540-1. We are looking to out-source our calibration activity and while some of our customers require that any company performing calibrations must comply [or in some cases, accredited] with ISO 17025, others cite ANSI Z540. Are there any substantive differences between the two documents and, if so, what are they?

As a background, our calibration needs include routine dimensional gaging, thrust load cells, pressure transducers, electronic instruments and chemical analysis instrumentation.

Jimmy Olson

Hi Paul,

Generally the 17025 standard is the perfered choice in the calibration industry as it is the newest one. ANSI Z540-1 was published in 1994 and is basically a compilation of MIL-STD-45662A and ISO Guide 25 (the old ISO standard for calibration). This publication was actually superseded by 17025 when it was published in 1999. I've heard rumors that the Z540 spec will dissapear, but I'm not positive on that. I hope this helps.


Ryan Wilde

ISO 17025 is the replacement for ISO Guide 25. It is less lax and adds several new requirements. ANSI/NCSL Z540-1 is ISO Guide 25 (with very few mild changes, otherwise it is word for word) with two sections added to the end to address requirements of MIL-STD-45662A, which is obsolete.

The Z540-1 is still a very active document, however. Government Agencies and their contractors still require compliance to Z540-1, because ISO 17025 does not address some of the issues in MIL-STD-45662A. Z540-1 is now very close to being reaffirmed (the vote has been taken) and will be a viable document until 2007, even though no realignment to ISO 17025 was made.

ISO 17025 is much more rigorous document, and those that are accredited by a competent accreditation body to ISO 17025 are nearly always in compliance with Z540-1 (it only takes a few minor additions to the 17025 quality system to comply with Z540-1). On the other hand, those that state compliance with Z540-1 rarely will be in compliance with ISO 17025, because the additional requirements are major, such as uncertainty calculation, method verification, software verification, etc.

Hope this clears it up a bit more,

Top Bottom