# Master Thermometer Calibration Range

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### #1 Kylo

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Posted 23 August 2018 - 03:24 AM

Hi all,
Currently we would like to calibrate thermometer by external party which will use as Master thermometer to 'calibrate' the working thermometer.

The temperature working range is -35, -21, 75, 300 degree C. I understand master unit should calibrate at a wider temperature range than working temperature.
External lab suggest the calibration point is -35, -18, 0, 150, 300 degree C.

Q1-how to set the min and max limit?

Q2- should i request calibration point extend to -40 instead of -35 degree C?

Q3- Is there any equation or standard to follow?

Rgds

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### #2 beautiophile

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Posted 23 August 2018 - 04:10 AM

Hi, the aim is to determine the reliability range of you measuring equipment. In chemistry, they use calibration curve the most. The reliability (dynamic) range shall cover entire working range, the answer of Q2 is Yes.

### #3 Charles.C

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Posted 23 August 2018 - 05:03 AM

Hi all,
Currently we would like to calibrate thermometer by external party which will use as Master thermometer to 'calibrate' the working thermometer.

The temperature working range is -35, -21, 75, 300 degree C. I understand master unit should calibrate at a wider temperature range than working temperature.
External lab suggest the calibration point is -35, -18, 0, 150, 300 degree C.

Q1-how to set the min and max limit?

Q2- should i request calibration point extend to -40 instead of -35 degree C?

Q3- Is there any equation or standard to follow?

Rgds

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Hi kylo,

It totally depends on what you plan to do with the thermometer, ie what specific temperatures you likely intend to monitor.

And possibly how accurately you will need to monitor them.

Kind Regards,

Charles.C

### #4 012117

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Posted 23 August 2018 - 07:16 AM

Depends on the criticality of the thermometers. If both extreme values are critical or needed in the operation for accurate monitoring, I'll have my master calibrated with values wider than what is needed in the operation becuase I will be checking/verifying as well my thermometers wider than its operational range.

### #5 Kylo

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Posted 24 August 2018 - 01:00 PM

Hi all
Well noted with thanks.

Rgds.

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### #6 redfox

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Posted 30 August 2018 - 01:00 AM

Hello,

Our practice is we have 1 set of thermometer per working range. Though much costly but we are more confident in our thermometer verification.

regards,

redfox

### #7 Kylo

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Posted 30 August 2018 - 05:37 AM

Hi redfox,
Would you mind to explain further as I couldnt get it.

Rgds.

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### #8 redfox

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Posted 30 August 2018 - 06:19 AM

Hello,

We have set of thermometer per working temp range. Ex: pasteurizing temp range 84-88C. We primary standard, secondary standard and the working thermometer. Primary standard is sent to TPL for calibration. The secondary standard is verified/calibrated against primary standard every month. The working thermometer is calibrated daily before the production commence.

Then we have another set of thermometer for our chilling tank temperature monitoring. Range is 0-4C.

Hope this may help.

regards,

redfox

### #9 Kylo

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Posted 01 September 2018 - 05:33 AM

Dear redfox
Thank you for the elaboration.
Any specific reason to have one set 'hot thermometer (pasteurization range)', another 'cold thermometer (chilling range)'.

Secondly, may I know reason to have secondary thermometer since working thermometer can verified monthly against primary thermometer as it is calibrated externally.

I plan to have a set of master/primary thermometer calibrate externally (which will not use for daily checking). Then monthly working thermoter will verified against master thermometer.

Rgds

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### #10 Charles.C

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Posted 01 September 2018 - 10:22 AM

Hi kylo,

If you are interested in the potential significance of what the thermometer is to be used for can browse through this thread -

http://www.ifsqn.com...ence-equipment/

Kind Regards,

Charles.C

### #11 Kylo

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Posted 02 September 2018 - 04:54 PM

Hi Charles,
Many thanks.

Rgds

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### #12 redfox

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Posted 03 September 2018 - 12:11 AM

Hello,

One reason is the cost. Since we are doing daily calibration on our working thermometer, the probability and risk of damaging your expensive primary thermometer is high, We have hot tank (84-88C) and chilling tank (0-4C) working temp range. Since it is calibrated on the working range, we are very confident on the result.

If you're only doing monthly calibration on your working thermometer, it may work best for you, but the common practice is primary, secondary and working thermometer.

regards,

redfox

### #13 Kylo

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Posted 13 September 2018 - 12:19 PM

Hi redfox
Thanks, appreciate it.

Rgds

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### #14 Kylo

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Posted 07 October 2018 - 06:35 AM

Hi all
Here I would like to seek your kind advice on few questions.

Below is the calibration results on master unit infrared thermometer.

Reference Test unit. Correction. Spec +-
-40.1 -41.2 1.1 2.0
-18.2 -19.6 1.4 2.0
0.0 1.3 -1.3 2.0
149.9 151.9 -2.0 3.0
300.2 303.0 -2.8 6.0
Measurement uncertainty +- 1.5 degree C

Q1- what does Spec +- 2, 3 or 6 degree C in report means?

Q2- if my acceptance tolerance is only +-1 degree C, how to set the correction? Is it taking max value -2.8 or average all 5 correction readings?

Q3- method to calibrate working infrared thermomter. We are using it to check blast freezer and cold room temperature.
Is it shoot the master & working unit at same spot, at the same time under the cooler units ( as this area is the warmest point).
If not, what is the right method.

I understand internal daily/weekly calibration is using hot water & ice bath.
Method is: insert the master unit and working unti in hot water and ice bath. Then check any different.
For cold temperature calibration, we are inserting it in ice flakes.
I would like to know it should insert in 'ice flakes' or 'ice flakes + water'?

Q5- is it acceptable to use calibrated master digital thermometer to calibrate working dial thermometer?

All input are welcome and appreciate.

Rgds

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### #15 Kylo

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Posted 07 October 2018 - 06:43 AM

Hi all
Resend the infrared thermometer results.

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### #16 Charles.C

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Posted 07 October 2018 - 08:44 AM

Hi all
Here I would like to seek your kind advice on few questions.

Below is the calibration results on master unit infrared thermometer.

Reference Test unit. Correction. Spec +-
-40.1 -41.2 1.1 2.0
-18.2 -19.6 1.4 2.0
0.0 1.3 -1.3 2.0
149.9 151.9 -2.0 3.0
300.2 303.0 -2.8 6.0
Measurement uncertainty +- 1.5 degree C

Q1- what does Spec +- 2, 3 or 6 degree C in report means?

No idea. Maybe a suggestion related to Q2.

Q2- if my acceptance tolerance is only +-1 degree C, how to set the correction? Is it taking max value -2.8 or average all 5 correction readings?

Yr thermometer has an accuracy outside your tolerance at several points, ie it is not acceptable at those points unless you change the tolerance.

Q3- method to calibrate working infrared thermomter. We are using it to check blast freezer and cold room temperature.
Is it shoot the master & working unit at same spot, at the same time under the cooler units ( as this area is the warmest point).

Yes. IMEX the door area is the warmest point.
If not, what is the right method.

I understand internal daily/weekly calibration is using hot water & ice bath.
Method is: insert the master unit and working unti in hot water and ice bath. Then check any different.
For cold temperature calibration, we are inserting it in ice flakes.
I would like to know it should insert in 'ice flakes' or 'ice flakes + water'?

The latter. Text boooks refer "melting ice".

Q5- is it acceptable to use calibrated master digital thermometer to calibrate working dial thermometer?

Assuming that yr objective is to determine whether the value indicated by the dial thermometer complies with its tolerance then yes.

All input are welcome and appreciate.

Rgds

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Hi Kyle,

See  ^^^^^.

Kind Regards,

Charles.C

### #17 beautiophile

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Posted 08 October 2018 - 01:29 AM

Q1- what does Spec +- 2, 3 or 6 degree C in report means?

Q2- if my acceptance tolerance is only +-1 degree C, how to set the correction? Is it taking max value -2.8 or average all 5 correction readings?

Q1+Q2: In my experience, there hardly is a fixed absolute value as the tolerance of such wide range. Fixing the ratio between tolerance and nominal values makes more sense.  The greater a quantity is, the greater its tolerance should follow. The "Spec" column looks like the accepted tolerances. The "Correction" is just the difference between the test and reference reads to compare with "Spec". And "Measurement uncertainty" means the error of the measuring method.

I understand internal daily/weekly calibration is using hot water & ice bath.

Method is: insert the master unit and working unti in hot water and ice bath. Then check any different.

For cold temperature calibration, we are inserting it in ice flakes.

I would like to know it should insert in 'ice flakes' or 'ice flakes + water'?

The importance is to keep the isothermal state in your bath. Therefore, you can add ice flakes as long as you stir the mixture well.

Q5- is it acceptable to use calibrated master digital thermometer to calibrate working dial thermometer?

Yes, when you prove the reliability of the master, no matter what its mechanism or its technology is.

Hope this help.

Edited by beautiophile, 08 October 2018 - 01:30 AM.

### #18 012117

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Posted 08 October 2018 - 04:53 AM

Hi all
Here I would like to seek your kind advice on few questions.

Below is the calibration results on master unit infrared thermometer.

If you could snip shot of the calibration, would be better to assist, IMO :)

Reference Test unit. Correction. Spec +-
-40.1 -41.2 1.1 2.0
-18.2 -19.6 1.4 2.0
0.0 1.3 -1.3 2.0
149.9 151.9 -2.0 3.0
300.2 303.0 -2.8 6.0
Measurement uncertainty +- 1.5 degree C

Q1- what does Spec +- 2, 3 or 6 degree C in report means?

In above, if you could give snip of the certificate, may assist you better :)  It could also be the preciseness of the value obtained at that point.

Q2- if my acceptance tolerance is only +-1 degree C, how to set the correction? Is it taking max value -2.8 or average all 5 correction readings?
Do you have as found and as left data? It seems your error already exceeds your tolerance. Normally for the correction, you do extrapolation from the curve you obtained from your calibration. If you have third party or in-house you may also want to discuss with them on how determine suitability of your measuring instrument.

Q3- method to calibrate working infrared thermomter. We are using it to check blast freezer and cold room temperature.
Is it shoot the master & working unit at same spot, at the same time under the cooler units ( as this area is the warmest point).
If not, what is the right method.

There is normally a "black box" for calibrating infra red thermometer. If you have calibrated it using the "black box" ( if that is what you referred to by the master) and you may want to clarify if you meant calibration and not verification. If you want to verify that they execute the same reading, then what you describe is correct.

I understand internal daily/weekly calibration is using hot water & ice bath.
Method is: insert the master unit and working unti in hot water and ice bath. Then check any different.
For cold temperature calibration, we are inserting it in ice flakes.
I would like to know it should insert in 'ice flakes' or 'ice flakes + water'?

the 2nd one. Air may affect your reading since you typically wont have the tight fitting "block".
Q5- is it acceptable to use calibrated master digital thermometer to calibrate working dial thermometer?
To verify the reading of all other working dial thermometer, yes. There are  some "rules" in calibration that the master should be about 4:1 with your other instrument. Should this not be critical to your process, then, yes.

All input are welcome and appreciate.

Rgds

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### #19 Kylo

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Posted 08 October 2018 - 09:56 AM

Dear all
Thanks for the advice. I would need to digest first.
Btw, today we did the working unit calibration.
Results like this.

Ice water:
Master unit readings= 2.9, 0.2, 0.3, 3.3
Working unit readings = 2.2, -1.3, -1.3, 2.7
May i know how to calculate the differences?

Is it (2.9-2.2)+(0.2- (-1.3))+(0.3-(-1.3)+(3.3-2.7), then divide by 4?

We took 4 readings per unit.

Sorry, this question may sound silly.
Thanks again.

Rgds

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### #20 Charles.C

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Posted 09 October 2018 - 11:44 PM

Hi Kylo,

It is usually recommended/stipulated that a unit intended to be a master thermometer be calibrated/documented by a 3rd Party using equipment traceable to NIST etc and under standard lab.environment.

Theoretically the temperature of "standard" melting ice should be 0.0 degC. Frequently it is not under yr setup.

So you have 2 errors to consider, that in the intended master and that in intended sub-master. Many quality thermometers offer a zeroing facility which the 3rd party will set upon request at one chosen point of interest.

Kind Regards,

Charles.C

### #21 Kylo

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Posted 11 October 2018 - 01:44 PM

Thanks to all.

Rgds

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