Development of MEMS-based thermal mass flow sensors for high sensitivity and wide flow rate range

In the natural gas trade, mass flow metering is preferred to volume flow metering. In order to improve the measurement performance related to sensitivity within wide flow rate range of the mass flow meter, a novel design of a MEMS-based thermal mass flow sensor is proposed. To determine of the correlation between the sensing performance and geometry of sensor components, in this case the heater and the thermopile, models with various designs were fabricated using MEMS technology. Flow characteristic tests of the fabricated models were conducted in the low pressure gas flow standard system of KRISS. The effect of the distance ratio between the heater and thermopiles on the measurement performance of the thermal flow sensor was examined according to the flow rate range. The results presented that the basic models with the different distance ratio show different sensitivity characteristics. The non-uniform model proposed in this study show high sensitivity in both low and high flow rate region compared with models with a certain distance ratio.