Gas metering is a big part of what we offer customers. One product that has proven to be very successful is the Honeywell Smart Multivariable (SMV) Transmitter. It is an industry leader – there are no others on the market that work as well. It measures the gas pressure & temperature and measures a differential pressure across a primary element. The primary element can be an orifice plate or a Preso Ellipse pitot tube. It creates a differential pressure that we measure and relate to flow (the square root of the pressure drop is proportional to the flow rate). The SMV calculates a corrected flow by accounting for the compressibility of the gas along with the pressure and temperature that exist in the pipe. It is quite an involved calculation that is pre-loaded into the transmitter and set up using a software wizard. Please keep it in mind for gas metering applications – it is an affordable alternative. For under $4000 you can measure big flows accurately with easy installation.