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Measuring instrument – calibration or legalization?

Calibration and legalization – these terms still cause much confusion and are misused. Their meaning has been defined in the VIM International Dictionary of Metrology Terms to match international standards. How do these processes differ from each other?

What is calibration?

Calibration is the process of determining the relationship of the values indicated by a calibrated device to a standard. The standards of a unit of measurement are usually determined by a higher grade device of very high accuracy, calibrated by a calibration laboratory with appropriate authorization.

Calibration device

What is the result of calibration?

The result of a calibration determines the deviation from the standard and the uncertainty of measurement of a measuring instrument. The calibration of a measuring instrument determines whether the instrument meets the specified metrological requirements and is suitable for performing the measurement.

Calibration certificate

A calibrated measuring instrument receives a calibration certificate. It is issued in accordance with the template developed by the Accreditation Center. The certificate contains the table of the performed measurements, measurement error and uncertainty estimation and information about used standards and the date of the test. It does not specify the validity date of the calibration, because it is determined by the user of the measuring instrument.


Calibration or adjustment?

Calibration is often mistakenly referred to as alignment, which is the adjustment of an instrument to restore the values specified by the manufacturer. This operation is correctly called adjustment. It is best done in a service or calibration laboratory of the manufacturer.

Calibration of measuring instruments – how often?

Main Office of Measures and calibration laboratories recommend calibration every 1-2 years. However, these recommendations may vary depending on the manufacturer of a particular instrument.

Label applied to calibrated device

The frequency with which a measuring instrument should be calibrated depends on, among other things:

  • relevance of the measurement accuracy for the instrument user

  • exposure to mechanical and chemical contamination

  • exposure to conditions of extremely high temperature and humidity

Legalization of measuring instruments

What is legalization? These are activities which include checking, stating and certifying with a verification certificate that the instrument meets the measurement requirements specified by the Minister of Economy. Instruments used in the protection of health, safety, environment and consumer rights, as well as those used for fee collection or customs control are legalized.

What measuring instruments require legalization?

These include:

  • water meters
  • conversion factors for gas meters
  • heat meters for water of nominal volume not exceeding 500 m3
  • gas meters
  • automatic and non-automatic weighing instruments
  • exhaust gas analysers
  • electronic taximeters

Legalization of water meters - what does it involve?

One of the instruments that requires regular legalization is the water meter. Legalization of a water meter is carried out every 5 years at points designated by the Central Office of Measures. When the device is found to be in working order, it receives a special marking, such as a burnt symbol, sticker or seal.

Legalization of scales - how long are they valid?

Legalization of new scales remains valid for 2 consecutive calendar years without the last month. The second and subsequent re-legalization should be performed before the expiration of 25 months, counting from the 1st of the month in which the re-legalization was performed. The expiration date is determined by the markings on the scales.

Calibration of JUMO measuring instruments

At JUMO, you can calibrate your measuring instruments. We offer services such as:

Calibration of temperature sensors

We offer, among others, the calibration of thermometers, Pt100/Pt1000 sensors, K- and J-type thermocouples. Moreover, we calibrate temperature sensors at any measuring point chosen by the customer - either on-site or in our calibration laboratory.

Calibration of humidity sensors

We offer calibration of hygrometers for direct humidity measurement, also with a transmitter and a data logger.

Calibration of pressure transmitters

In our laboratory we measure negative overpressure and positive overpressure in the range from -1 to +10 bar.

Calibration of pressure gauges

Directives and standards, e.g. ISO 9001, require manufacturers to calibrate pressure gauges. You can order a pressure gauge with a calibration certificate from JUMO. We also calibrate pressure gauges from -1 to +10 bar.

Need more information?

When you got questions about calibration, you can contact us and ask your questions through this form.

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About the Author

My name is Saskia van der Laan, I have been working for JUMO for over 33 years. Since 2012 I have been working with great enthusiasm in the marketing department. It is my passion to use written text to translate technology into practice with the aim of informing and inspiring the reader.


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