Precise setting of a measured value by professional intervention in the measurement system. For balances: Either with an external test weight using the adjustment function (CAL or CAL key), or with the automatic internal adjustment or adjustment control. This is necessary following changes in temperature, changed environ-mental conditions, change of location, etc. daily routine checks are recommended. The term “calibrating” was formerly also used for adjusting., but today it means something else (see above).
Calibration is the testing and determination of the precision of a measure value without intervention in the measurement sys-tem. The calibration certificate contains the measured value with information on the relevant measuring uncertainty. If appli-cable, a statement can be made as to whether this is within tolerance limits. Industry requires calibration of measuring devices, in order to, for example, be able to connect parts manufactured at different locations without encountering problems. Calibrations must be repeated at appropriate time intervals, for which the user is responsible. KERN recommends that, with intensive (daily) use, you recalibrate the measuring devices every 6 months and with normal (weekly) use, every 12 months.
Confirmation of the achievement or compliance of a predetermined standard, such as a DIN standard such as DIN EN ISO 9000 ff. (Quality management) or DIN EN ISO/IEC 17025 (Accreditation), or a build-type approval for balances.
Every body experiences a relatively small loss of weight in air (buoyancy). This must be taken into account for accurate weighing procedures. In order to avoid this “distortion” in daily use, all weights are adjusted to the unit specifications as given in R111 OIML recommendation. (air pressure 1.2 kg/m³ and material density 8000 kg/m³)
DAkkS calibration is carried out for measuring devices, reference materials and material measures for particular measurement sizes and measurement ranges, which are defined individually for every laboratory as part of their accreditation. The issued DAkkS calibration certificates are proof of the metrological traceability to national and international standards, as required, for example, by the DIN EN ISO 9000 and DIN EN ISO/IEC 17025 standards. DKD calibration has no legally regulated period of validity. The operator is responsible for observing an appropriate time for recalibration. Usually the recalibration period is approx. 1 year.
Factory calibration certificates
The testing of measuring devices for accuracy in accordance with a recognised, but not accredited, process – this is the difference when compared with DAkkS calibration. ISO calibration certifi-cates are also referred to as factory calibration certificates.
International validity of DAkkS calibration certificates
DAkkS is represented in the EA (European co-operation for Accreditation) as well as in the ILAC (International Laboratory Accreditation Cooperation). This ensures that DAkkS calibration and DAkkS calibration certificates are recognised and valid almost anywhere in the world.
It is determined for each balance according to a precisely given test method and documented in the Calibration certificate. It depends on various factors, both internal and external. The measuring uncertainty of a measuring device is an objective measure of its accuracy and is therefore an accurate statement for its appropriate use.
Monitoring checking equipment
This is a mandatory requirement of quality Management Systems.
OIML (Organisation Internationale de Métrologie Légale) has representatives from almost 100 states who work on unified build and test regulations for all measuring devices. In the OIML certification system the certificates issued by the member states certify that a particular measuring device build type is in accor-dance with the OIML recommendations. In this way, a build type which was tested and approved in one country, can be approved in another country without having to repeat the test. (Excerpt from PTB). The OIML R111 guideline defines the construction-related characteristics for test weights, such as material, upper surface texture, markings, construction, shape etc.
The pre-requisite for all perfect measurement is the complete, continuous proof, that a measuring device can be traced to international or national standards. The most important standards demand that all check ing equipment (e.g. test weights) meets the national or international standards in accordance with defined tolerances. In weighing technology, these standards are the test weights. They are traced back to the national test weight in the PTB (Physikalisch Technische Bundesanstalt) in Braunschweig, which in turn is derived from the original kilogram in Paris. In this way, incorrect measurements through inaccurate checking equipment is avoided.
A verification, called "evaluation of conformity" for new conceptuality, means the official examination of the accuracy of dimensions, weights, balances and measuring tools according to the law of dimensions and weight. The verification is required by the state and protects consumers. Only balances with approved design and only weights according to OIML of classes E2, F1, F2 and M1 can get a conformity assessment.