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Thermometer Calibration for -70 freezer


Julie D.

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I am looking for suggestions on how to calibrate thermometer'sfor my department ultra- low freezer. I say that I should test my NIST and testthermometer in the same medium (i.e. glycol) but my laboratory managerdisagrees. My other question is what is the acceptable difference between mytraceable NIST and my test thermometers at -70?:confused:

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I have been placing my NIST thermometer into the freezer with the thermometer I'm qualifying for use, and use a +/- of 1C as my acceptability parameter. It has worked so far. It does take a little while to get from room temp to the -70C range but it does work. We are in the process of converting to a wireless monitoring system which sends us NIST validated probes on an annual basis. That will save a lot of time.

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We just finished the install with Checkpoint wireless. I'm still working on getting the probes placed in the appropriate spots so that we can get a consistent temperature reading. We are about a month away from starting our validation of the system.

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  • 2 weeks later...

(Please note I am the Operations Director and Deputy Quality & Technical Manager for ISO/IEC 17025:2005 at Tempsys which makes the CheckPoint Wireless Monitoring System)

As has been mentioned, having a new or re-calibrated NIST traceable probe sent to you is the simplest solution and definitely worth $40. Calibrating probes in an ice bath for 0C is fine however I don't recommend trying to perform comparative measurements for -70C unless you're familiar with measurement uncertainty and calibration procedures. Our probes are spec'd at +/- 0.5C although Dan's +/- 1.0C should be fine since most departments set their low/high alarms at -80/-60.

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