Natural gas measurement today is accomplished through the use of two different classes of gas meters. These are inferential type meters, which include orifice and turbine meters, and positive displacement meters, which include diaphragm and rotary displacement meters. The inferential type meters are so-called because rather than measuring the actual volume of gas passing through them, they “infer” the volume by measuring some other aspect of the gas flow and calculating the volume based on the measurements. The positive displacement type meters are so-called because they measure the actual volume of gas displaced through them