6.2.6 Where appropriate, measurement equipment having a significant influence on the results of the inspection shall be calibrated before being put into service, and thereafter calibrated according to an established programme.
6.2.7 The overall programme of calibration of equipment shall be designed and operated so as to ensure that, wherever applicable, measurements made by the inspection body are traceable to national or international standards of measure¬ment, where available. Where traceability to national or international standards of measurement is not applicable, the inspection body shall maintain evidence of correlation or accuracy of inspection results.
In an inspection body, the inspectors use thermometers to measure the ambient temperature or to measure the temperature of raw milk in a cisterna or the temperature of hot water used to sterilize equipment in a slaughterhouse.
The inspection body gives its thermometers to a related accredited testing laboratory for calibration. The calibration is performed by means of an internal reference thermometer, which is calibrated by an external accredited calibration laboratory. Acceptance criteria are set by the testing laboratory but there is no indication of measurement uncertainties.
The result of the testing laboratory is a report of confirmation that the individual thermometer can be used again for above stated purposes.
Question: Is this approach acceptable. If not, why?
March 2017
There are certain aspects to be regarded:1. The Inspection procedure shall clarify whether the temperature measurements have significant influence (ISO/IEC 17020:2012, clause 6.2.6 and ILAC P15 §6.2.6 n3)
2. Calibration needs to calculate calibration uncertainties. If this is not done, it is not a calibration.
3. Acceptance criteria need some information about calibration uncertainty.
4. External calibration has to follow rules from ILAC P10: Calibration by NMI or accredited calibration laboratory has to be preferred.
5. Internal calibration using a traceably calibrated reference thermometer is allowed. The internal calibration procedure shall be assessed by a competent person of the accreditation body. Remarks:
a. The mentioned related test laboratory is certainly not entitled to sell accredited calibrations.
b. The “related accredited testing laboratory” might be a part of an internal calibration procedure. In this case the calibration has to be assessed by the accreditation body. This would be ok.