Hi folks,
I have a couple of questions please. I have to provide advice to a space simulation vibration lab that is contractually required to have their test equipment calibrated to a 17025 Accredited level by an accredited facility.
1. If the pressure standard they are using to calibrate their accelerometers is calibrated at a "17025 accredited" lab, if they then use it to calibrate accelerometers locally does the accreditation transfer? My thinking is that it does not because their lab is not accredited, etc.
2. Does anyone know where I can find a good web link or a really good metrology reference book that talks about transference? I'd like to brush up on the specifics of:
How the transferrence occurs.
What qualifies a standard as a transfer standard, etc. :?
I know that you have to use a standard of greater accuracy, etc. but I really need something in writing with "specifics" as I am setting policy for a large facility and want to make sure that I am "correct" without any doubts.
I care about doing a quality job.
Thanks for your inputs and have a great weekend!
Opera Diva! :-)
As to 1. I don't believe it will, as I am understanding your statement the facility in question has an accredited standard, that's nice however they are not accredited (or at least they are not accredited to test accelerometers). That is to say they cannot issue documents with certain logo on it generally accepted as evidence compliance to whatever.
There are provisions for exceptions, for instance we have some equipment that we cannot get accredited but we were able to verify all equipment that was used to test it was accredited so we were able to use it.
Can't comment on the other.
My two cents is that if the requirement is to have their test equipment cal'd to ISO17025, it must be done by an accredited lab. A calibration is only considered ACCREDITED when done by an accredited lab within their scope of accreditation.
You can use an accredited standard to do a cal, and depending on what the letter of the contract is, it may or may not be sufficient. But it is definitely not an accredited cal unless under the above accredited conditions.
QuoteWhat qualifies a standard as a transfer standard, etc.
In my opinion, stability. If you have an instrument that is repeatable for the duration of your transfer, then you have a good transfer standard. It doesn't even necessarily need to be accurate. Precise, yes. But repeatability and reproducibility are what you need to transfer any measurement from a standard to a UUT.
QuoteA calibration is only considered ACCREDITED when done by an accredited lab within their scope of accreditation.
Agreed!
This answer is actually simpler than everyone is thinking.
The is no such thing as an "accreditation transfer" The closest thing any 17025 AB allows is if a Company purchases an pre-exisiting accredited lab. And that is a very temporary situation.
With 17025 you are either accredited, or not. There are no funny if, and, but, rules. If it is not on "YOUR" scope, than it is not accredited. It does however allow for calibration of in house standards, but those calibrations will be a part of your next assesment, and must fully comply with all of 17025 anyways, so you may as well just get accredited.
Your last few questions on the forums leads me to beleive that you should take a serious look at calling up a 17025 consultant.
When using a transfer standard, you must also have direct access to a reference standard. Both of the transfer situations you have mentioned do not fit this requirement. You can not transfer the accuracy of a reference you do not have on hand. Transfers usually are only used in situations where the reference, and the unkown cannot, or should not be directly connected. Transfers also generally have very short stability times as in less than 24 hours. Most are used within minutes of the reference measurement.
I have quite a bit of experience going through the process of accreditation as QA manager of a commercial calibration laboratory. I would be happy to lend any assistance.
Mike Frisz
(407) 706-0328
Hi Guys,
Thanks for all of your great inputs! I appreciate your time very much!
?? Does anyone know of some type of reference/reading material that refers to
Standards, how transfer standards work, and/or the Principles of Metrology?
I have an old Fluke "Calibration-Philosophy in Practice hand book and some old Navy Elec. tech books, but nothing more as reference material.
Can anyone suggest anything?
Do any of the old PMEL books cover this? Perhaps I can find them at the government publication stuff.
Thanks for any input.
OperaDiva :-)
QuoteDoes anyone know of some type of reference/reading material that refers to Standards, how transfer standards work, and/or the Principles of Metrology?
I would recommend you get a copy of "The Metrology Handbook" from ASQ. Vaisala also puts out an easy to read "Calibration Book" (DOC 213538) that you can order or download online at http://www.vaisala.com/instruments/calibrationbook.html
Hey Dave,
Thanks for the input! I've got the Measurement and Calibration Handbook from Keesler, but the other reference materials you talked about will be such a further help!
I appreciate your input!
Have a great day!
Opera Diva :-)
OD1-
If you are a member of NCSLi, you may want to check out the Recommended Practices (RP's) Library. There is extensive information there of the metrological concern. My team and I are using the RP's to help align our lab to Z540.3 requirements.
Good tip Rocket. I forgot all about those resources. They are quite helpful.