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Calibration Range for Measuring Equipment


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#1 jeremyyap

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Posted 28 September 2010 - 10:00 AM

Hi , i would like to know if the measuirng equipment calibration range has been established for the Thermometer from -20°C to 350°C. During the audit, found that the result of calibration range was from -18.95°C to 349.15°C. Is this accepted as the calibration was not carried up to the specified requirement of -20°C and 350°C?

Kindly advise.

Thanks & Best Regards,
Jeremy Yap


#2 DebD

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Posted 28 September 2010 - 03:12 PM

Hello Jeremy,

I would say that this would be acceptable as long as the temperatures you are measuring are within the calibrated range. I would be interested to know other opinions on this as this is what I have worked to in the past!

Also is there anything on the calibration certificate that states if there is a tolerance on the specified requirements?

regards,

DebD

Hi , i would like to know if the measuirng equipment calibration range has been established for the Thermometer from -20°C to 350°C. During the audit, found that the result of calibration range was from -18.95°C to 349.15°C. Is this accepted as the calibration was not carried up to the specified requirement of -20°C and 350°C?

Kindly advise.

Thanks & Best Regards,
Jeremy Yap



#3 Charles.C

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Posted 28 September 2010 - 08:59 PM

Dear jeremy,

I am no statistical expert but I think you are possibly over-simplifying the situation. The "acceptability" depends on a combination of factors.

For example, one can calibrate any thermometer at 0degC but most text books will recommend rejection of the thermometer if the necessary correction exceeds +/- 1 or sometimes +/- 0.5degC. Similarly for weighing instruments.

Although you refer to a range, i presume the actual calibration was done at certain fixed points accessible to the official calibration instrument (sometimes people also use blackbox electronic temperature simulators, not sure if this is allowed in official procedures though).

I think, at a minimum, if you are "quoting" a range, the calibration procedure is strictly required to include the actual intended temperature of usage. Additionally, for example, if your instrument is calibrated at 0degC / 100degC and you are using it at 50degC the appropriate required correction will be rather uncertain, the uncertainty depending on the absolute correction factors (CF) at each end. It is rare to find the CF equal so it is common to specify a further calibration point close to 50degC in such circumstances.
Nonetheless, i seem to recall experiencing the same problem as you indicate at -20degC due to the official procedure simply not having access to such a temperature or a nearby colder value. If so, presumably an auditor will hv to accept unless the absolute correction at -18.95degC is astronomic (?)

The usability of calibrated measuring equipment thus depends on overlapping items such as -

Approximate temperature to be measured
Required accuracy for the measurement
necessary correction at defined points as per the calibration procedure
validity of calibration, eg probability data generated by calibration, traceability of utilised calibration equipment

Rgds / Charles.C


Kind Regards,

 

Charles.C


#4 AS NUR

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Posted 29 September 2010 - 01:22 AM

Hi , i would like to know if the measuirng equipment calibration range has been established for the Thermometer from -20°C to 350°C. During the audit, found that the result of calibration range was from -18.95°C to 349.15°C. Is this accepted as the calibration was not carried up to the specified requirement of -20°C and 350°C?

Kindly advise.

Thanks & Best Regards,
Jeremy Yap


Dear Jeremy..

IMO.. After calibrate your thermometer, ussualy the calibration body will state the uncertainty of your thermo .. as your data i guess your uncertainty is ± 0.95 C.. so.. you have to compare to your standard.. if your standard range bigger then your uncertainty.. you can accept that calibration..but if your range lower then uncertainty you cant accept it..

i.e your temp. standar range is 100 ± 1 C and the uncertainty is ± 0.95 C.. thats mean your thermometer is capable and accurate to measure the temp. so you can accpet it.

Hope can help you..:thumbup:

rgds

AS Nur

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