As a source of energy, gas is becoming more and more important both in the domestic and industrial sectors. The consumption of gas can be measured with the help of turbine gas meters, diaphragm meters, rotary meters and, since recently, also ultrasonic meters. In order to determine the accuracy of a volume or flow meter (test meter), it is compared with a calibrated gas meter (master meter). In this process a test rig is used to generate several

different flow rates and to register the deviations between the test meter and the master meter. A test rig contains several master meters with different measuring ranges in order to cover as large a range of flow rates or volume measuring ranges as possible.