Equipment Calibration

Equipment Calibration

Calibration is a comparison between measurements – one of known magnitude or correctness made or set with one device and another measurement made in as similar a way as possible with a second device.

In daily usage, consistent differentiation between the terms calibration and adjustment is frequently neglected.

Calibration involves ascertaining and documenting deviation of the measured value from a retraceable, highly accurate test standard. The measured value obtained from a measuring instrument is thus compared with the known value of the test standard under specified reference conditions using reproducible measuring procedures. Calibration does not involve any manipulation of the measuring instrument, which remains entirely unchanged.

Adjustment involves the correction or balancing of a measuring instrument in order to eliminate systematic measurement deviation. The measured value obtained from a measuring instrument is thus adjusted to match the known value of the test standard under specified reference conditions. Adjustment always involves manipulation, which permanently changes the measuring instrument.

Retraceability of a calibration procedure means that the calibration sequence is reproducibly documented from the individual device under test all the way up to the national standard for the respective measured quantity. Retraceability of measurement results is assured by a country’s metrological infrastructure.

Why do measuring instruments have to be calibrated?

As a standard for quality management systems, ISO 9001:2008 stipulates essential requirements for monitoring measuring instruments in section 7.6, insofar as they are used to assure compliant results, and thus uniform product quality as well. Measuring instruments must be retraced to national standards at regular intervals by means of calibration, and if necessary adjusted, and plainly labeled with their calibration status. If it is determined during calibration that the measuring instrument does not fulfill the specified requirements, the operating company must evaluate the validity of previously obtained measurement results and implement appropriate measures with regard to the measuring instrument itself, as well as all affected products.

Consequently, calibration at regular intervals assures the quality of the respective product or service on the basis of internationally comparable measurement results. This provides for legal security with respect to product liability, as well as for approval tests and audits.

Due to its assured retraceability to national test standards, Arrelic calibration is advisable for the recalibration of measuring instruments which, in turn, are used as test standards for monitoring other measuring and test equipment.

Calibration Intervals

Time between any two calibrations of measuring and test instruments is known as the calibration interval and must be established and monitored by the user in accordance with his own requirements. Essential criteria for determining the calibration interval include:

  • Measured quantity and permissible tolerance
  • The extent to which the measuring and test equipment is subject to stressing
  • Frequency of use
  • Ambient conditions
  • Stability of previous calibrations
  • Required measuring accuracy
  • Company-specific requirements specified by the quality assurance system

We recommend a calibration interval of 1 to 2 years for use under normal conditions. We recommend a calibration interval of 1 year for measuring instruments which are used on a regular basis for audits, evaluating work safety and assuring the quality of products and services, as well as under severe ambient conditions.

Arrelic has in-house competency to perform calibration of instruments ranging from Dimensional, Pressure, Flow, Temperature, Humidity, Electrical, Torque, Force and Mass.

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