questions RE: instrument calibration

Does anyone know the procedures for certification of testing equipment so as to maintain ANSI, MIL, ASTM, NIST, and ISO standards? Are there any crossovers so that if one is ISO and MIL, that one is also automatically ASTM, etc.?

For example, what is the schedule for calibration of equipment? Does it need to be done by an independent, or can I utilize strict procedures and thoroughly train someone to do this in-house? We want to do it right and the annual expense is somewhat unreal.

Thanks.

 

[AJohnson]

There is no direct and easy answer to your question. Somtimes qualifying to one code or organization allows qualification to another code, but not always. Historically, MIL specs were usually the most stringent, and qualification to a MIL spec calibration procedure would meet the requirements of NIST, ASTM, ISO 9001 etc..., but just because you met the stringent MIL specs didn't mean you got the other qualifications...you still had to show the other organizations that you had already achieved qualification to a more stringent standard and ask for their approval of your system. Sometimes all it would take was a letter, other times not.

With the changes brought about by MIL spec reform in the early 90s, many MIL specs have adopted commercial specs that were in use and just added a couple of extra qualification items. In other cases some MIL specs were adopted by industy, e.g. ASTM, and became the industry norm. The main goal was to reduce the amount of government expense at maintaining a vast standards library that was often times already repeated in industry.

You can see some MIl specs at

http://astimage.daps.dla.mil/quicksearch/

Go there and type in 38793 in the document number block to get a manual on how to write your calibration manual.

Also try 1839 to get MIL-STD-1839 and MIL-HDBK-1839, which deal with standard practice for calibration and measurement requirements. Andy

 

[Ron]

One approach you should consider is to write your own internal calibration manual that gives the frequency and level of calibration of your equipment. Different equipment, depending on level of use, type of equipment, specification tolerances and other variables, will require calibration at different intervals.

One key to a valid calibration program is its traceability. For instance, all calibrations should be traceable to a recognized standard, such as NIST.

ASTM and other standards organization usually provide performance, not calibration requirements. As an example, they might dictate the physical dimensions of a piece of test or measurement equipment, with allowable tolerances, but not the calibration method or requirements.