Why should I calibrate the instrument?
The calibration of measuring tools is indispensable for the fulfilment of UNI EN ISO 9001, which in section 7.6 deals with the management of the measuring equipment.
The first section of paragraph 7.6 of UNI EN ISO 9001 says as following: "The organization shall determine the monitoring and measurement activities to be performed, as well as the monitoring and measuring equipment necessary to provide evidence of product conformity to the specified requirements". As a result, the company must identify the equipment necessary for various process steps during product realization, and submit it at specific calibration intervals to a laboratory.
Not only the tools needed for the various controls and testing phases, but also all the tools used at various steps of the product life cycle, including design, will be considered. Internally, the company have to draw up an instrument tab, where it will report, in addition to the identifying data of the instrument itself, the maximum errors allowed for each metrological characteristic that will be checked. This is necessary to perform metrological validation of the instrument itself.
The second section of paragraph 7.6 of UNI EN ISO 9001 states that: “The organization has to establish processes to ensure that monitoring and measurement can be, and are, carried out in line with monitoring and measurement requirements".
Therefore, a process must be a series of operations to ensure that measurements are performed in accordance with the requirements for these activities, as reported in the application of UNI EN ISO 10012: "Measuring Management Systems - Requirements for Processes and measuring equipment".
What does it mean to calibrate an instrument?
The calibration is to identify metrological characteristics of a measuring instrument. That is the "photograph" of the instrument in its current state. Consequently, the calibration is simply a comparison with a reference sample and it does not contemplate the adjustment of the instrument.
The aim of calibration is to verify accuracy (error), that is the difference between the value detected by the instrument and the known value of reference sample, hence the term “with reference to acknowledged samples”. We must not confuse calibration with adjustment: while calibration isan operation that allows you to define the metrological characteristics of an instrument, the adjustment aims to make the device more accurate, so it is about the relationship entry/exit of the instrument in order to improve its performance.
Where it is necessary and where possible to make adjustment, the sequence of steps shall be as follows: initial calibration ---> adjustment ---> final calibration. The adjustment service, where possible, is excluded from the instrument calibration service and must be expressly requested by the customer and quoted separately.