Temperature and Humidity Effects on Measurement Devices

[CaliperJim]

Our calibration process is subject to NAV04 Calibration. Items 7.a asks "Where [a controlled environment] is not possible are the environmental effects monitored and recorded to correct measurements results?". I'm struggling to find the coefficient for thermal expansion for devices such as calipers and micrometers. Does anyone have experience in determining the effects of temperature and humidity on common measurement devices? I seriously doubt Florida summer weather is enough to require compensating corrections for calipers but I need to know for sure. Thanks.

 

[John C. Abnet]

Good day caliper Jim;
Instead of determining the thermal expansion for devices (even then, different materials, manufactures, etc...will of course, all be different), I would suggest including a study as part of your MSA. Since the goal is always to determine if the correct device has been selected and it is providing the intended results, why not develop a study comparing results during various conditions to see exactly how much variation is being realized so that your organization can make the proper decision based on that data?

My thoughts.
Be well.

 

[greif]

There is inherent uncertainty in expansion coefficients (due to material variation). In uncertainty calculations, 10% potential error is often used for the stated coefficient of expansion. So, a general valuer for steel, for aluminum, for soda lime glass, etc. is often good enough. Most users consider measuring a steel part with a steel tool , good enough to not require thermal calculations (assuming acclimation).

 

[jerry bambach]

The effect of thermal expansion is the temperature Delta of a Micrometer made of steel and an Artifact made of steel is the same, so if you have a
1 deg F delta, then you would have a 6uin per inch error. For other materials, you need to look up their expansion in the engineer's Handbook
Jerry Bambach

 

[CaliperJim]

The effect of thermal expansion is the temperature Delta of a Micrometer made of steel and an Artifact made of steel is the same, so if you have a
1 deg F delta, then you would have a 6uin per inch error. For other materials, you need to look up their expansion in the engineer's Handbook
Jerry Bambach

Thanks. Which Engineer's Handbook?

 

[jerry bambach]

This may help as it is a table. The Handbook would cost about $200, but you may find it in the library. Thermal Expansion Coefficient - Table this is online and you can find and it Free

Jerry B

 

[dwperron]

Our calibration process is subject to NAV04 Calibration. Items 7.a asks "Where [a controlled environment] is not possible are the environmental effects monitored and recorded to correct measurements results?". I'm struggling to find the coefficient for thermal expansion for devices such as calipers and micrometers. Does anyone have experience in determining the effects of temperature and humidity on common measurement devices? I seriously doubt Florida summer weather is enough to require compensating corrections for calipers but I need to know for sure. Thanks.

I am including a link to a public A2LA document on the calculating measurement uncertainty for several basic dimensional tools. They give an overview of how to handle the uncertainty contributors, including temperature for hand tools with some assumptions added for ease of calculation, and they also give a specific example for calipers.

Enjoy.

https://a2la.qualtraxcloud.com/ShowDocument.aspx?ID=5658