A gas meter is a device that monitors how much of a fuel, such as propane or natural gas, flows through a specific pipe. Utility companies that provide gas service use meters to determine usage and charge users accordingly. Some industrial plants use gas meters as a means of monitoring flow, usage, and judging the performance of a pipe system. There are many different types of gas meters, each using a separate mechanism to measure usage.
Gas is quite different than other measurable liquids. Highly susceptible to heat changes and pressure, the volume of gas may be difficult to measure accurately. Meters must be customized to accommodate for factors like heat and pressure in order to give accurate readings.
Most residential homes are supplied with gas by utility companies that use a form of measurement called a diaphragm gas meter. These meters have special moving parts — diaphragms — that expand or contract as gas flows through them. Each time they expand or contract, it pushes the usage measurement dial or bar slightly higher. These meters are quick and easy to read, and are usually checked once a month or every two months by gas company employees.
Rotary meters are somewhat similar to diaphragm gas meters but have a different mechanism for measurement. Instead of using expanding or contracting parts, they allow gas to flow through a chamber with spinning rotors. As the rotary spins, the data is transmitted to a counter. The measurement given by a rotary gas meter is actually based on the amount of spins completed by the rotors.
Though not always accurate, an orifice gas meter is preferred by many industrial companies because it is simple to replace and has only one basic part. The device consists of a straight pipe where gas is directed around a carefully designed flow disturbance, almost like a rock in a stream. The pressure of the gas over the disturbance is used to create the usage readout.
Some advanced types of gas meter actually require computer programming to work correctly. Ultrasonic gas meters do not measure the amount of gas used, but instead get information on usage by measuring the sound waves in the pipes. Sound speed alters depending on volume, so accurate readings of flow and amount, as well as pressure readings, can be taken using this type of metering. Ultrasonic gas meters are often attached to computers rather than having manual readouts, as the necessary computations are quite elaborate.