Mercury in Glass Thermometer Uncertainty Budget

[Silverhill]

Hi All,

Can anyone assist me in a simple example of an uncertainty budget for a mercury in glass thermometer calibration against another mercury in glass thermometer already calibrated?

I would be most grateful for any help as this is the first time I have had to produce an uncertainty budget in the laboratory

Thanks in advance

 

[Hershal]

Silverhill,

This is not a comprehensive answer, just a basic one. A comprehensive one would require a lot of space.

The first thing about uncertainty budgets is to understand what the influences are and how they affect the measurement.

On a liquid in glass comparison to liquid in glass, the obvious biggest contributor is temperature control. It is not the only one of course. Soak time, how the items are handled, micro-cracks, even the medium (the liquid itself) are contributors. What equipment is used to effect the comparison, different techs, different times of the day all can have an effect.

Once the influences are identified, then try to quantify them. You may not succeed with all of them.

The calculation is done after the influences are identified and quantifed. I recommend downloading the Measurement Uncertainty Calculator version 3.2 available from the Agilent website. It is no-cost, and is a good program.

You can of course look at the GUM (Guide to the Expression of Uncertainty in Measurement), in the U.S. sold as ANSI/NCSL Z540-2-1997. If you manage to stay awake past the first three pages, let everyone know.....you might be the first.

Hope this helps.

Hershal