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2 point vs 3 point thermometer calibration


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Jackson Tsang

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Posted 16 October 2014 - 12:22 AM

If I need to measure temperature of frozen, chill and cooking temperature, does it mean I need to calibrate 3 point of -18C, 0C & 100C?

I have heard of two point calibration may be somehow good enough, say 0& 100. Any suggestion?

Calibration of 18C need to do externally and cause hesitation...



Mike Green

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Posted 16 October 2014 - 10:30 AM

If I need to measure temperature of frozen, chill and cooking temperature, does it mean I need to calibrate 3 point of -18C, 0C & 100C?

I have heard of two point calibration may be somehow good enough, say 0& 100. Any suggestion?

Calibration of 18C need to do externally and cause hesitation...

I think the record  low temp for multiplication  of bacteria  (generally) is -15c  (Planococcus sp)- for pathogens I believe it's closer to -1.5o c (listeria sp) -though i have heard anecdotally as low as -5 (citation needed)

 

& I personally have never encountered 3 point calib. happening outside of a research lab so....(based on that) from a safety perspective-  I wouldn't worry too much about it!

 

 

Mike


I may sound like a complete idiot...but actually there are a couple of bits missing

Charles.C

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Posted 16 October 2014 - 01:51 PM

Dear Mike/Jackson Tsang,

 

(shortened version sincethe forum system just deleted my first post)(Grrr).

 

I routinely use 5 point calibration, -18, 0, 10, 90, 100 (degC).

 

Method - set up one certificated master thermometer and generate sub-masters.

 

It logically also relates to the accuracy required for the intended application. For example, IMEX most TCs have  insuffiicient accuracy  for CCPs / Validation if using 0/100 degC only and at intermediate/external values.

 

(-18degC "area"  may be required to monitor freezing capabilities / validate cold rooms)

 

Rgds / Charles.C


Kind Regards,

 

Charles.C


KTD

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Posted 24 October 2014 - 03:16 PM

I utilize both 2 and 3 point calibration checks, based on the intended device application (as Charles.C mentioned). If using a thermometer/thermocouple for a narrow temperature range (processing 'room' temp, cook temp, freezing temp) I have typically used a 2 point calibration that brackets the anticipated min/max temp range. When using a device measuring a wider range - cold and hot temps, I use a three point calibration: bracketing the extremes and then one point in or around the middle of that range. I have found this methodology supportable, ensures sufficient accuracy, and not excessively time-consuming.

 

Keith



gboskou

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Posted 04 November 2014 - 12:20 PM

better not use the same thermometer for a wide range

choose one for cold and one for hot ranges

if you are using a an accredited thermometer as reference for calibration

this is attached with an accreditation report demonstrating the temperature range of accuracy

I suggest that you prefer more practical reference temperatures, related to common practice e.g. -18 for deep freezer, 4 for refrigeration, 15 for cold cabinets, 63 for hot cabinets, 75 for pasteurization or cooking etc.

in that way your calibrated thermometer will be more related to your application

 

 

 



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