Unsourced material wheatstone bridge calculations pdf be challenged and removed. Gases are more difficult to measure than liquids, because measured volumes are highly affected by temperature and pressure. Gas meters measure a defined volume, regardless of the pressurized quantity or quality of the gas flowing through the meter. Temperature, pressure, and heating value compensation must be made to measure actual amount and value of gas moving through a meter.
Several different designs of gas meters are in common use, depending on the volumetric flow rate of gas to be measured, the range of flows anticipated, the type of gas being measured, and other factors. Gas meters that exist in colder climates in buildings built prior to the 1970’s were typically located inside the home, typically in the basement or garage. Since then, the vast majority are now placed outside though there are a few exceptions especially in older cities. These are the most common type of gas meter, seen in almost all residential and small commercial installations. Rotary meters are highly machined precision instruments capable of handling higher volumes and pressures than diaphragm meters. With each turn, they move a specific quantity of gas through the meter. Turbine gas meters infer gas volume by determining the speed of the gas moving through the meter.
Because the volume of gas is inferred by the flow, it is important that flow conditions are good. A small internal turbine measures the speed of the gas, which is transmitted mechanically to a mechanical or electronic counter. These meters do not impede the flow of gas, but are limited at measuring lower flow rates. Orifice meters are a type of differential meter, all of which infer the rate of gas flow by measuring the pressure difference across a deliberately designed and installed flow disturbance. The gas static pressure, density, viscosity, and temperature must be measured or known in addition to the differential pressure for the meter to accurately measure the fluid. They are however accepted and understood in industrial applications since they are easy to field-service and have no moving parts. Ultrasonic meters measure the speed of gas movement by measuring the speed at which sound travels in the gaseous medium within the pipe.