ENMO Services’ lab is accredited to ISO17025, including associated specific standards ISO16063-21:2003 and ISO16063-44:2018. From various national guidelines, users of accelerometers, force cells, vibration meters and vibration calibrators are urged to have an accredited calibration performed to ensure legitimate and correct measurements. The customer receives a full certificate with each calibration, stating that the measuring equipment functions within expectations.
That all sounds very clear and straightforward, but it is not that simple. The challenges involved in calibrating this equipment are considerable. Despite accreditation and the accompanying quality system, the ENMO Services lab is still learning every day. Standing still is going backwards and quality is a continuously improving process.
Due to the lab’s independence, the knowledge and skills of different brands are necessary. This provides the challenge of properly building product information, procedure and device manuals. From these, the correct specifications, such as tolerances, limits and ranges, must always be derived, which are translated into the calibration procedures.
Similarly, correct agreements on mounting, torque value, cable handling are very important to establish correct frequency response of an accelerometer, especially higher frequency. Combine this with a triaxial accelerometer, which usually has to be mounted with vacuum grease, so the seismic center has to be found correctly, and a difficult and very accurate measurement awaits the calibrating service engineer. Agreeing how exactly to do this is a matter of thorough training combined with sufficient guidelines to ensure repeatability over several calibrations, between different competent persons.
Continuous monitoring of the stability of the measurement system is also a challenge, to keep reporting correct and accurate results at all times. After all, the measurements should only reflect the fluctuations of the object under test, obviously no deviations in the measurement system.
Because the scope vibration, which is described in less detail in the accompanying standard than noise, more customer questions arise about rejection criteria and/or whether the measuring equipment is still usable within their application. An important but also challenging task for the ENMO Services lab is to guide customers in a correct way.