Are intermediate checks required for calibration laboratories?

A calibration includes evaluation of measurement uncertainty and provides metrological traceability to SI units. The purpose of intermediate checks is to maintain confidence in the calibration status of measuring and test equipment in-between calibrations. This, for some applications may be daily, and others before use. An example is the verification of the performance of a calibrated balance by using calibrated mass pieces in the working range for the measurement. Where results are favourable, intermediate checks can provide justification for the extension of calibration intervals.

All laboratories, both testing and calibration must have a procedure to perform intermediate checks when necessary to maintain this confidence in the performance of equipment. “When necessary” will depend on the nature of the equipment and the purpose of the measurement. When a calibrator (reference standard or certified reference material) is used every time before a measurement, a calibration is being performed – no need for any “intermediate” checks.  

For more information on associated calibration intervals, refer to ILAC G24:2007 Guidelines for the determination of calibration intervals of measuring instruments (note currently under revision) available for download at https://ilac.org/?ddownload=818 
and the ISO 17025 document template: Equipment and Calibration Procedure at https://advisera.com/17025academy/documentation/equipment-and-calibration-procedure//