Abstract: There is disclosed methods and apparatus for proving fluid meters, particularly gas meters of the positive displacement, diaphragm-operated type in which the number of cycles of operations of the valve mechanism of the meter is used as a factor in proving the accuracy of the meter, the number of said cycles being determined by sensing a series of pressure waveforms in the test gas entering and leaving the diaphragm chambers of the meter, which waveforms are characteristic of the particular meter being tested and occur in each cycle and reoccuring cycle of operation of the meter when operating, detecting a characteristic waveform in each series of waveforms, amplifying and shaping the characteristic waveform and counting a predetermined number of cycles of said waveforms and comparing the volume of test gas which has passed through the meter as measured by a test bell with the amount that should have passed during that predetermined number of cycles of operations of the meter.