Every measuring instrument needs calibration and every calibrated instrument needs to be re-calibrated. This means that there is a due date for a re-calibration period that we need to establish.

This recalibration period is a scheduled calibration that is based on the calibration interval that we set. Before we send our instruments for calibration, we need to set in advance our initial interval or our final fixed interval. This will be communicated with the calibration lab.

These initial calibration intervals may be based on the following aspects:

1. Manufacturer Requirements – recommended by the manufacturer

2. On the frequency of use – the more it is used, the shorter the calibration interval

3. Required by the regulatory bodies (for example: required by the government)

4. Experience of the user with the same type of instrument

5. Based on the criticality of use. – more critical instruments have higher accuracy or very strict tolerance, therefore shorter calibration interval

6. Customer Requirements

7. Conditions of the environment where it is being used.

8. Published Documents

Now that we have an initial calibration interval, we need to set the fixed calibration interval based on the performance of our instruments. We will review the performance by gathering all the calibration records and plot it in a graph to study its stability or the drift encountered by the instruments.