Mass Flow Sensor Using Dual SAW Device

The application of SAW devices to a thermometric mass flow rate meter with a reference channel for temperature compensation is presented. The sensor is composed of a delay line device with two channels, namely a reference channel that does not come in contact with the fluid and a sensing channel that makes contact with the fluid. The mass flow rate of gases can be obtained by measuring the temperature change of the device caused by drawing heat from the surface with constant temperature due to the fluid. The results obtained from flow rate measurements of several gases demonstrate that the proposed device is effective as a flow rate meter. Moreover, it is also shown that the response characteristics to mass flow rate changes and the response stability for fluids were improved by taking the phase difference between the signals of the reference channel and the sensing channel as the gas flow rate.