LIG thermometer calibration-complete immersion

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LIG thermometer calibration-complete immersion

Postby Graham Webster » 2013 Apr 23, 19:49

I recently had my dry-bulb, wet-bulb, max and min liquid-in-glass thermometers calibrated in a UKAS laboratory at 5 points across the scale. They are the sheathed/Met office type. I got a tinytag on loan from COL while my LIGs were away.
The thermometers were partially immersed to a depth of 55mm. On the certificates of calibration there is a column marked 'Emergent Column Mean Air Temp'. I think this is okay in the lab but no use in the field. The thermometers are nearly 25 years old and this is the first time they have been calibrated. Of the 4 tested, 3 were found to be outside the manufacturers tolerance of 0.2C. The 'max' had the largest error, 0.5C at 20C.

I have been doing a bit of research on this and LIG thermometers that measure air temperature are complete immersion thermometers. Partial or total immersion thermometers are used to calibrate other sensors. So, I will be returning the LIGs to the lab for re-calibration by complete immersion. The company is doing it free of charge.
The partial immersion might explain why 3 of my 4 LIGs were found to be outside the 0.2C tolerance and why the errors are not linear across the scale.
Graham Webster
 
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Joined: 2012 Sep 04, 17:11
Location: Baintown, Fife. 125m asl. Firth of Forth, 3km to south-east. Hill, 205m asl 1km to NNW.

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