Guidance on the re-verification of EPOS Systems after a software alteration or update

19th Aug 2011

The following guidance notes relate to the procedures that should be followed after the software on an EPOS system (connected to an EC type approved and verified NAWI) that is typically found in a supermarket, which has been updated or altered.

It is the view of the UKWF that the changes made in respect of the EPOS would not require a full "re-verification" of the NAWI-EPOS combination, as the metrological aspects of the weighing machine (which bears all of the required "marks") should not have changed and are still compliant with the requirements.

 It is felt that a full re-verification would only be required if the "instrument" had been found not to comply with the requirements, e.g. outside of the MPE (Maximum Permissible Error), or there had been a repair or modification (e.g. re-calibration) to the weighing element.

It is important that "sufficient" checks, and records of those checks, are maintained to ensure that the instrument is compliant with legal requirements after the software changes have been made. These checks may be conducted on a random sample of the instruments to ensure that:

    • the NAWI continues to respect the MPE ('simple' weighing check);
    • the NAWI-EPOS combination is operating correctly, and;
    • data from the weighing machine is producing the correct "output" e.g. price calculation, printout, etc.

If at any point you form the view that any alteration, adjustment, addition or repair may have affected the accuracy or functioning of the instrument, it is likely that a full re-verification would be required. More detail on this can be found in bulletin WM 1003 on the National Measurement Office website.

If you have any further questions on this please do not hesitate to contact me.


Ian Turner
Technical Officer

Industry Associations