10.11.2008
A new test equipment for gas meters with temperature control of the test air between -40 °C and +80 °C was put into operation in 2008, and first serial examinations of laminar flow elements have been successfully carried out as part of a degree dissertation.
The conformity assessment according to the European Measuring Instruments Directive (MID) requires - especially for gas meters - tests of the measuring accuracy to be performed in the whole range of the nominal operating conditions. These conditions cover a temperature range of -40 °C to +80 °C, which implies metrologically complex measurements. To ensure our competence, an appropriate test equipment was set up in the "Gas Flow" Department, which is suited for the examination of measuring instruments up to size G160 within the whole temperature range required, with a measurement uncertainty of 0.25% and less. As shown in the conceptual drawing, dried compressed air is used to avoid condensation.
Figure 1: Conceptual drawing of the temperature test facility for gas meters
Critically operated venturi nozzles serve as flow rate standards, which are calibrated with inlet pressures of maximally pabs = 8 bar.
During the past months, the testing of the subsystems was successfully completed, and a first serial examination of the temperature-dependent behaviour of laminar flow elements could be successfully completed as part of a degree dissertation. The results reflect very well the temperature-related viscosity and density changes of the test air.
For next year, first requests in connection with conformity assessments according to MID and OIML have already been made.
Contact person:
Rainer Kramer, FB 1.4, AG 1.42, E-mail: rainer.kramer@ptb.de