Calibration of ergometer test facilities now carried out by Working Group "Torque Realization"

According to the Medical Devices Act, foot pedal ergometers are considered as "medical devices with a measurement function". The rotational power provided by the patient is measured as a product of momentary rotation speed and acting torque. The standard to which all calibrated ergometers are finally traced back is now operated at PTB by the Working Group "Torque Realization".

So far, this standard belonged to Division 8, Working Group 8.12 "Standards for medical instrumentation" in Berlin-Charlottenburg. It had to be calibrated at regular intervals, the main effort being the tracing back of the torque measuring chain. This led to the fact that the standard and the person in charge had to go to the Working Group "Torque Realization" in Braunschweig at regular intervals to carry out this connection.
In the course of reorganization, placing the operation of the ergometer standard in other hands was considered. The Working Group "Torque Realization" was quasi the natural address, and the implementation was agreed on. After the question of the premises had been solved the measuring facility was moved to Braunschweig in October 2008. A first calibration of a client's test facility was successfully carried out in January 2009 with the support of Working Group 8.12.
The standard for the rotation power measurement ("ergometer standard") shown in the middle of Figure 1 has the following metrological parameters:
- Measuring range: 10 W ... 1000 W
- Expanded measurement uncertainty: 0.3%, minimum 0.3 W (k = 2).
According to the Medical Devices Act [1] and the Medical Devices Operator Ordinance [2], foot pedal ergometers used for medical purposes must undergo a metrological check at least every two years. This check must only be carried out by authorities competent for legal metrology or persons having the necessary qualification for metrological checks.

Figure 1: Ergometer standard for the power measurement up to a maximum of 1000 W, on the left: a foot pedal ergometer (the pedal arms and pedals are removed for the calibration, the bottom bracket shaft is directly connected with the standard)

[1] Medical Devices Act, came into force on January 1, 1995, last update of August 7, 2002, last amended on June 14, 2007 (Fed. Law Gazette - BGBl. I p. 1066) - in German

[2] Ordinance on the Production, Operation and Use of Medical Products, came into force on July 7, 1998 (Fed. Law Gazette - BGBl. I 1998, p. 1762), last amended by regulation on November 25, 2003 (Fed. Law Gazette - BGBl. I p. 2304) - in German

Contact person:

D. Röske, Div. 1.2, WG 1.22, E-mail: dirk.roeske@ptb.de