When natural gas passes through a meter, a pressure drop occurs. This pressure drop must be as low as possible because it takes energy to move the gas through meter; high meter pressure drops mean high gas transmission costs when many thousands of meters are taken into account. Yet gas meters often operate at high static pressures. Verifying the low pressure drop across a meter at its operating pressure is an important diagnostic. How can the low pressure drop across the meter be measured if the line pressure is several hundred psig?

A differential pressure transducer is the best way to measure small pressure drops across the gas meter, even at high static pressures. In a differential pressure transducer, there are two ports: + and -. The transducer is plumbed across the gas meter such that the + port is on the upstream side and the – port on the downstream side. The difference in the pressure applied to each port is the pressure drop through the meter. If the upstream side is 500 psig and the downstream side is 499 psig, there is 1 psi of pressure drop across the meter.

A differential pressure transducer is capable of having a full scale of, say, a few psid, while operating at static pressures of several hundred or thousands of psig. The output of the DP transducer reflects just the pressure drop of interest.