Thermal mass flow sensor

摘要

A mass flow sensor includes a semiconductor substrate (1), an insulating thin film (2), heaters (311,312), temperature measurement resistors (321,322), and a protective layer (4). The heaters (311,312) are formed on the surface of the insulating thin film (2), and are provided adjacently such that the heater (311) is provided upstream the heater (312). A cavity (5) is formed below the heaters (311,312), and the heaters are thermally insulated from the remaining portion of the semiconductor substrate. The temperature measurement resistors (321,322) are formed on the top surface of the insulating thin film (2), and are provided at opposite sides of the heaters (311,312), such that the resistors are aligned with respect to the flow passage of a fluid. In the mass flow sensor and the mass flowmeter including the sensor, the flow rate and flow direction of a fluid can be detected by means of merely the heaters (311,312), which are active elements. Therefore, the sensor and flowmeter exhibits highspeed response with respect to change in the flow rate of the fluid. <IMAGE>