Certificates of approval usually comprise:
- a certificate including the advice and conditions of approval
- a technical schedule that describes the pattern and any variants
- a test procedure with the tests (not already covered by other published test procedures) used to verify the instrument and the maximum permissible errors of the instrument.
The types of certificates are:
- certificates of approval for a specific variant of measuring instrument
- supplementary certificates of approval for pattern approved modules that connect to measuring instruments
- general certificates for instruments made to a common standard.