Gas flow sensors, often also referred to as mass flow meters, work by calculating moving gas volumes in a pipe or confined space while accounting for variables of temperature and pressure. Various methods are employed for gas flow sensors to produce accurate readings. These include measurement using sound waves emitted and collected by ultrasonic transducers, and gas flow meters that measure the actual total mass that passes a certain point.
Flow meters come in a range of designs and measurement capabilities. The Coriolis flow meter employs the Coriolis effect with moving bodies by measuring fluid mass based on the vibrations it causes in tubes as it passes by, through analyzing the wave patterns the vibrations produce. Like ultrasonic flow measurement, Doppler flow meters also analyze sound waves based on the Doppler effect to calculate mass through changes in frequency and amplitude of the sound waves as the mass flows towards and away from the Doppler gas flow sensors. Variable flow meters are also often employed as gas flow sensors, requiring a simple float device in the tube that is moved by the force of the gas volume as it passes by.
Liquid flow sensors, by contrast, can usually be of simpler design, as liquid flow is more gradually affected than gas by temperature and pressure fluctuations. Since gas flow sensors are built primarily to measure volume and not the thermal quality of a gas, such as in natural gas used to heat homes and cook with, calculations based on the actual economic value of the gas must also vary due to its composition. The elements contained in a gas volume can vary significantly even if the volume itself does not change. Utility providers, therefore, incorporate pressure controls into the gas flow, and regularly perform a gas chromatograph spectrum analysis to determine the actual chemical makeup of the gas flow.
Aside from sound-wave-measuring gas flow sensors, others devices utilize diaphragms in the pipe that respond to pressure and produce pulses that are fed into a flow computer for volume calculations. Rotary and turbine gas flow sensors use the mechanical motion of spinning impeller and turbine blades to determine volume flow. Orifice meter gas flow sensors use a more narrow region of the pipe to create a pressure differential, which is compared to the pressure in the standard pipe diameter. While orifice gas flow sensors are considered less accurate than other sensors, they are widely used in industry as they have no moving parts that can fail.