Calibration of measuring instruments

Our calibration laboratory is responsible for ensuring the metrological traceability of a measuring instrument or sensor to a national primary standard, through a chain of comparisons, all with a declared degree of uncertainty.

Calibration is performed in most cases by means of a comparison measurement: a reference sample, with known and certified characteristics, is compared with the instrument to be calibrated; operating at different points of the area to be measured, the two measurements returned by both instruments – the reference sample and the measurand – are then analysed simultaneously in order to record the difference between the values. The calibration report expresses, with different criteria, the value of this difference, for each measured point. Each measurement made is accompanied by the uncertainty estimate.

The reference sample, which has more advanced metrological characteristics than the measurand, must ideally be calibrated as the primary standard (by Accredia – the Italian Accreditation Body); the error that the operator introduces with reference to the test conditions that are adopted at the moment of performing the calibration will then be added to the measurement error indicated in the relative Calibration Certificate. The entire measurement error will be reported in the measurand calibration Report or Certificate.

The result of a calibration operation can be:

A Calibration Certificate. In this case, the laboratory must have UNI CEI EN ISO/IEC 17025 accreditation and the procedure relating to the calibrated quantity must be included in the Accreditation table published on Accredia’s website. The acronym used to identify Accredited laboratories is LAT (Laboratorio Accreditato di Taratura – Accredited Calibration Laboratory), followed by the Centre Number. Unilab’s Calibration centre number is LAT 229.

A Calibration Report. In this case, the setting for which the calibration result is required to contain a chain of comparisons with stated uncertainty is kept constant. However, the document is not drawn up in accordance with an Accredia-approved procedure, but according to technical procedures established internally by the laboratory, which usually fall within an ISO9001 certification range.

The presence of an Accredia accreditation guarantees that the technical procedures necessary to perform the calibration with the correct metrological traceability have been conducted correctly, but also – and above all – certifies the technical competence of the personnel who carried out the calibration operation.

Instrument calibration – temperature

Calibration service for temperature sensors, thermometric chains and thermometers

Our laboratory has a portable testing bench, equipped with a PT 100 temperature sensor which serves as a primary reference. With this, we can conduct calibration operations – even at our customer’s premises – in temperatures ranging between ambient temperature and 550 °C.

Where this service is carried out at our client’s premises, the certificate is issued at the same time as calibration and is available on our Unilab portal.

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