Newsletter: Accredited Cal Certs |FAQ's
Quite simple ...
an accredited CalCert can be issued only by ISO 17025 calibration laboratories with validated and audited calibration procedures, e.g. international acknowledge standards. The competence of the laboratory to perform validated calibration procedures for specific dimension (SI units) is audited by the one and only national accreditation body, in Germany the DAkkS (Deutsche Akkreditierungsstelle GmbH).
This is to make sure that all results captured with calibrated measuring instruments are traceable to the international standards of metrologie (ILAC and the national metrologie institutes like PTB).
In chapter 220.127.116.11.2 the requirement for external laboratories is stated as follows: "External, commercial or independent testing laboratories shall be either [...] accredited to ISO / IEC 17025 or a comparable national standard - the relevant test, measurement or calibration service being included in the scope of the accreditation (of the certificate). The calibration certificate or test report shall bear an accreditation mark (a seal) of the national accreditation society. [...] "
Accreditation of a calibration laboratory follows the international standard DIN EN ISO 17025, which states the requirements in regard to the management and competence of the entire organisation. In Germany some 442 calibration laboratories are accredited by DAkkS. (Oktober 2017)
The most comprehnsive listing can be found in the DAkkS database.
Whether the laboratory of your choice is able to deliver a traceable and accredited calibration certificate, can be sorted out by answering the following questions. (All neccessary information can be found in the accreditation certificate of your laboratory.)
The Accreditation Certificate always shows the measurands and sometimes also the objects the calibration laboratory is accredited for.
The annex to the accreditation certificate lists the standards and procedures under which the calibration is carried out in the column Messbedingungen/Verfahren (measuring conditions / procedures). You may find this reference on the second page of your calibration certificate. These clear standards and procedures should ensure that calibration certificates from different laboratories can be compared.
The column Messbereich/Messspanne (measuring range / measuring span) shows the lowest and highest value, traceble to the national metrology institute. E.g. calibration of force gauges with a nominal capacity F(nom)=10 N, can be performed in laboratories accredited with 2 N minimum load only.
If your instrument is stated with a measuring tolerance of 0,1% and the best measurement capability of the laboratory is 0,1% also, the certificte may not show the conformity of your measuring instrument with the technical datas and your requirements. Therefore you always should make sure that the BMC of the laboratories equipment and procexdures is much better, than the tolerance of your measuring instrument.
The so called ISO-Calibration-Certificate is a marketing term for a non-accredited certificate. These calibration procedures and the calculation of uncertainty are not specified in acknowledged standards and are not audited by independend experts of the national accreditation body. Even if the calibration laboratory is accredited according EN ISO 17025, does a non-accredited ISO-calibration certifate not meet the requirements according IATF 16949:2016.
No! As long as the caliberation procedures are identically, the expenditure to performe the calibration and to issue the calibration certificate is solely depending on the efficiency of the laboratory and organisation. Additional costs result by the frequent auditing by experts of the accreditation body only.
These costs are usually added. Calibration laboratories issuing many certificates for a specific measurand are in most cases insignificantly more expensive then non-accredited calibration certificates without ILAC seal, as long as the calibration procedures are the same.