There is no rule that establishes the calibration frequency of measuring instruments (unless specific rules). Recommendations and advices on how to set this frequency can be given after the metrological confirmation system has been regularly put into operation.The choice of calibration intervals has to be made depending on several variables and must be estimated in any case so that the instrument remains within the assigned metrological capabilities.

The most important elements in order to choose the calibration intervals are:

  • Information and recommendations provided by the manufacturer
  • Instrument frequency of use
  • Type of instrument and tendency to wear according to use and / or storage conditions, it is also important to define the instrument drift over time
  • Usage and environmental conditions (temperature, humidity, vibration, etc.)
  • Accuracy of desired measurements
  • Any technical standards applicable to the instrument and / or internal standards
  • If the instrument presents errors and uncertainty limits greater than those accepted
  • Shocks, falls, any mechanical or electrical shocks, adjustments, maintenances, improper use, harsh and / or incorrect storage conditions for instrument.

The normative UNI 10127-2: “Guide to the Measurement Range for Measuring Instruments. Recommended intervals for linear, angular and geometric measurements” gives some references to the initial selection of calibration intervals for some instrument types. These tips can be varied depending on factors listed above. However, it is advisable to use intervals not exceeding 3 years.