Calibrator control
The trueness of the calibrator reference signal must be evaluated as part of the Internal Quality Control practice. Measurements must be performed by using an instrument with stated uncertainty of readings no worst than that specified for the calibrator reference value.
- The results of such control measurements shall be recorded using Control Charts and maintained in a special record.
- Whenever an out of control case is revealed the calibration service must be halted, and both the calibrator and the control measuring instrument shall be sent to a certified supplier for further external calibration and or repair.
For internal quality control on calibrator trueness you can use Shewhart charts (see an example built up using Microsoft Office Excel to control the value of + 5 VDC from a calibrator)