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.