| 摘要 |
There is disclosed herein methods and apparatus for proof testing 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 reoccurring 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 meter prover with the amount that should have passed during that predetermined number of cycles of operations of the meter. In the embodiment herein disclosed, the proving of the meter is carried out by maintaining a predetermined constant rate of flow of the test gas through the meter as by placing a sonic nozzle, a critical flow orifice or the like in the path of the test gas, such as air, which passes through the meter being tested for a measured length of time whereby the volume of the test air which actually passed through the meter may be determined to establish the proof of the meter.
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