Development of a MEMS Gas Flow Sensor Unified with an Impurity-Gas Concentration Sensor

Abstract

Thermal conduction type gas flow sensor unified with an impurity-gas concentration sensor using the MEMS processing technique is proposed. This unified sensor has a pair of returning groove channels, and each channel has a sensor-unit composed of a central thermocouple and a pair of thermocouples formed by both sides of the central one. The central thermocouple is working as both a heater and a temperature sensor working as a current detection type thermocouple. This unified sensor can measure both carrier gas (H2) flow and impurity-gas concentration. The impurity-gas is mixed on the way into the H2 carrier gas. The extremely compact sensor with high sensitivity is able to realize. The carrier gas flow is measured using one of sensor-units, and the impurity-gas concentration is obtained from measurement of differential temperature difference between two central thermocouples of sensor-units in the cooling process after cease of thermocouple-heating during stopping the gas flow.