Understand everything about the calibration of measuring instruments

Expert advice from LAB SERVICES

Measuring devices are at the heart of many industries. The accuracy of these instruments is fundamental. Entrusting the calibration and control of measuring instruments is an option that interests many professionals. Do you need to have your measuring instruments calibrated? Are you looking for a calibration service provider? Here is the advice of Lab services experts that will allow you to clearly identify the guarantees and guarantees of quality of your calibration service provider. 

What is calibration?

Calibration compares a number of readings from the instrument to an (inter)national standard. The determination of deviations can be made by a direct comparison with the (inter)national standard but is also possible using a series of comparisons with derived standards. If there is a chain between the calibration of your measuring instruments and the (inter)national standard, the calibration of your instrument is traceable to the (inter)national standard.

Examples of international standard standards are the official kilogram and meter, both kept in Paris.

Euro-Index reference standards are all calibrated in a traceable way, so that the calibration of your measuring instrument is traceable to (inter)national standard standards. The deviation is mentioned on the calibration certificate so that you know exactly the measurement uncertainty of the instrument compared to the true value.


The first manipulation performed (if feasible) is the precalibration. The deviation of the measuring instrument is noted for the period closing that of the last calibration. It is determined whether the deviation is acceptable (calibration). If the instrument is within specifications, it can be assumed that this was the case throughout the previous period.

Example of pre-calibration:

A 2.00000 bar pressure standard is connected to the instrument and it displays 1.928 bar. The difference is 0.072 bar. This is outside the specs of the device.

Adjustment and post-calibration

If it appears during precalibration that the deviations are larger than specified, then an adjustment of the instrument is necessary. In addition, it is also necessary to take into account the fact that the deviation observed is applicable to the measurements carried out previously with this instrument. 

Adjustment means that the instrument must be adjusted in order to measure as accurately as possible in accordance with the manufacturer’s specifications. Not all calibration laboratories are always able to do this! There is often a lot of specific knowledge and software, as well as spare parts and training needed to do this. An authorized service centre, such as EURO-INDEX, has this knowledge.

Calibration in a nutshell

The calibration of a measuring instrument is an operation consisting of measuring the same quantity with the equipment to be calibrated and the standard equipment, and comparing the indications of the two instruments, then using the results of this comparison.

Its use makes it possible, by applying systematic corrections, to reduce the uncertainty associated with the measurements. Calibration generates a numerical result.

The result of a verification makes it possible to verify that the means of measurement satisfies or does not meet previously fixed requirements. Satisfying the requirements authorizes the commissioning (or re-commissioning) of the measuring instrument. Verification can also be performed by comparing the results of the สอบเทียบเครื่องมือวัด calibration to the permissible error limits.

Why is calibrating your measuring instruments important?

First of all, the calibration of measuring devices meets strict obligations relating to compliance with ISO 9000 type Quality systems. The monitoring of measurement means by specialists makes it possible to guarantee that the devices are suitable and to certify that the results of the measurements , checks and tests are reliable.  

What is the calibration certificate and how do I obtain it?

The purpose of a calibration certificate is to provide the user of a means of measurement with the result of his calibration, allowing him to take into account deviations in accuracy when using it. In practice, the measuring instrument is compared to a standard. For each test point, the value displayed by the device, the value provided by the standard and the uncertainty on the value provided by the standard are noted.

This translates into a numerical result, which makes it possible to assess the error. At the end of this operation, a calibration certificate is issued showing all the test points and the numerical result of each test. No judgment is made on the device. A calibration certificate therefore does not guarantee that an instrument is “within specifications”.

This service is intended to make better use of an instrument. Knowing the error of the device, we are able to correct the raw result and reduce the uncertainty of a measurement. Calibration also makes it possible to follow the evolution of a device over time. 

What is COFRAC accreditation?

The French Accreditation Committee (COFRAC) is an accreditation issued to laboratories after audit. This accreditation is “recognition of its ability to perform calibrations for a given quantity with its associated uncertainties.

The competence and experience of the personnel, the equipment, the methods of calibration used and the connections to national standards are the essential elements on which accreditation is based.

A COFRAC calibration is the guarantee that the instrument has been calibrated “in accordance with the rules of the trade”. It is therefore of course necessary to contact a calibration laboratory with this accreditation. 

LAB SERVICES: calibration services

Lab Services operates in several sectors of activity, such as printing, the automotive sector, painting, plastics processing, cosmetics, etc. Whatever the brand of your instruments, a team of specialists intervenes on your means of control, directly on your site or within the laboratories.

  • All of the calibration services offered are carried out in accordance with the ISO 17025 standard.
  • All calibration services give rise to the issuance of a calibration certificate, and/or a verification report ruling on compliance.

As far as maintenance interventions are concerned, the aim is to check the proper functioning of the measuring means and to rule on their conformity according to their characteristics.

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