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  Measurement, Test and Calibration
  Calibration temerature and humidity requirements

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Author Topic:   Calibration temerature and humidity requirements
pooldude44646
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posted 14 December 2000 01:31 PM     Click Here to See the Profile for pooldude44646   Click Here to Email pooldude44646     Edit/Delete Message   Reply w/Quote
I am involved in coordinating calibration procedures for calipers, micrometers, etc. One question that arises...what is the temperature and humidity requirements for performing calibration on mechanical types of equipment? Is it 68-75 degrees F and 35 +/-5%? Other than contacting the manufacturers of the equipment, how can I determine the proper parameters? I thank you in advance for your help.

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Jerry Eldred
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posted 14 December 2000 02:09 PM     Click Here to See the Profile for Jerry Eldred   Click Here to Email Jerry Eldred     Edit/Delete Message   Reply w/Quote
One simpler method would be 'benchmarking' some accredited labs who do dimensional calibrations with equivalent or narrower critical parameters.

I am not a dimensional guru. I can keep up with the best of them on the basic dimensional calibrations, but take my reply in that context.

Another method would be to use the critical tolerances and temperature gradients on the most sensitive standard. You can intuitively divide your standards and workload into those most sensitive to environmental changes and those that are not. gage blocks are a good example of a critical parameter. Depending on what level of accuracy you are using them for will determine how much temperature gradient you can allow. That's an oversimplified answer, and there are probably some better informed answers out there who are gurus in that area.

Hope this is of at least some help.

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Alf Gulford
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From:Portland, OR
Registered: Aug 2000

posted 14 December 2000 02:18 PM     Click Here to See the Profile for Alf Gulford   Click Here to Email Alf Gulford     Edit/Delete Message   Reply w/Quote
I'm probably even less informed than most people posting replies here but thought I'd pass along that we've written our procedures to allow for calibration under a variety of circumstances and locations. I think the intent is that the mikes/calipers/gage pins/etc. can be calibrated or certified in the same settings in which they're used. Not very elegant but it seems pretty practical.

This has survived ISO 9001 registration and several subsequent audits.

Alf

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Ken K
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From:Wisconsin, USA
Registered: Jun 2000

posted 15 December 2000 01:08 PM     Click Here to See the Profile for Ken K     Edit/Delete Message   Reply w/Quote
Recommended temperature/humidity levels are 68 +/-1 degree F and humidity not to exceed 45%.
This was quite the issue during our last audit. This is the recommended temp/humidity for calibration labs, but for material testing, GM require's 23 +/-2C and 50 +/- 5% and Ford 21 +/- 2C and 50 +/- 5%.
Since most of our time is spent testing materials, we keep our lab at about 21.5C and 48%, which is above the recommended calibration levels.
Our auditor went over 6 years of temp/humidity data which we record two times per day. This data was from 3 different locations the lab has been in. (we move alot) He spent well over an hour trying to pin us with a nonconformance. The funny thing is, he all of a sudden dropped it and moved on to a different subject.
The main thing is to document the temp/humid levels of your lab. Take a reading in the morning and one in the afternoon.
Hope this helps somewhat. I'm sure your situation might differ.

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Patrick.Riordan
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From:Hattiesburg Mississippi
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posted 01 February 2001 03:52 PM     Click Here to See the Profile for Patrick.Riordan   Click Here to Email Patrick.Riordan     Edit/Delete Message   Reply w/Quote
Depending on your application the most important requirement is temperature. The specified temperature of measurement is 68 degrees F or 20 degrees C. The requirements for dimensional checking are at 20 +/- 1 degree C. This can have a major impact if you are measuring gage blocks, pin gages or operating a CMM without temperature compensation. For everyday instrumentation like dial calipers this is nt as critical. The constraint on humidity is impacted if the materials that you are measuring are impacted by humidity and dimensions could be changed by additional moisture. Beyond that you really don't want to run a lab on the dry side because you don't want to generate static electricity and zap delicate electronic gages. At the same time you don't want sweat dripping off the calibration tech caused by maintaining a tropical environment. If humidity is not critical to your process this can be covered by keeping it at a setting you feel personally comfortable with.

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