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Calibration Check on Periodic Inspection of Wet-bath Simulator

Tip 27: Does the Inspector use a traceable reference thermometer, that is accurate and precise, to at least two decimal places, to verify, annually or semi-annually, that the wet-bath and any other accessory equipment continue to meet the manufacturer’s specifications?

Digital thermometer
Are police using a NIST traceable reference thermometer reliable to two or three decimal places (one more than the display) to periodically check the temperature calibration of the Guth digital simulator?

As noted in an earlier tip, the manufacturer's specification for Guth 2100 temperature stability is 34.00 ±.05° C. and not 34.0 ±.2° C.. Unless a police or other Inspector is using a traceable reference thermometer, with two decimal point or better accuracy and precision, police are not "inspecting" in accordance with the ATC best practices.

The optional yellow NIST traceable mercury thermometer that police may have purchased, as an accessory from Guth, reads to one decimal place, not two or three. Note that the image below has been significantly enlarged. Reading such a thermometer with the naked eye is very difficult.

Mercury thermometer
Image of author's NIST traceable thermometer in Guth simulator

The OPP should be commended for beginning semi-annual inspections using a reference thermometer, similar to the one pictured at the very beginning of this blog entry, with two decimal place precision. I understand that the new OPP electonic thermometers AND THEIR PROBES are traceable to NIST on a one or two year interval. It remains to be seen whether OPP continue to maintain, inspect, and re-calibrate such electronic thermometers as required.

It is important to note that it is all of the following that need to be inspected whenever a wet-bath simulator is inspected:

1. the simulator temperature stability at 34.00 ±.05° C.

2. the digital thermometer to one decimal place

3. the RS232 thermometer to two decimal places

4. any optional yellow NIST thermometer to one decimal place

In the same way that the simulator temperature stability at 34.00 ±.05° C. cannot be inspected using a one decimal place mercury thermometer, a two decimal place RS232 interface thermometer cannot be inspected using a one decimal place mercury thermometer.

Municipal police services in Ontario need to learn good best practices from the OPP.


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