Normally we suggest to perform a bump test in normal measure mode with a CalCheck SF6 attached to the probe. If the bump test is not within the tolerance level (approx. +/- 5 .. 10 %) than we suggest to perform a calibration.
The frequency of bump test is in relation to the user profile of the instrument. For example, if the instrument is being used as a service instrument for field use, it should be tested before it is sent out. On the other hand a production instrument should be tested either every morning or every week.
The calibration of the instrument is quite stable and we believe the clients will find out rather quickly if they need to perform a test every morning or every week.