Sensor for mass flow regulator, esp. for controlling gas flow rate - has surrounding housing covered with thermal insulation plate and has sensor tube arranged in and projecting through housing

摘要

The sensor has a coil (14) lying upstream and a coil (15) lying downstream are wound around the sensor tube (13). The coils are arranged to determine the gases flowing through the sensor tube. A thermo-electric converter (19) converts the heat difference (T) between the heat (T1) determined by the upstream coil (14) and the heat (T2) determined by the downstream coil (15) into a voltage. An amplifier (17) amplifies the output voltage of the converter. A lineariser (18) linearises the amplified voltage from the amplifier. A cooling unit (21) maintains the inner temp. of the sensor system at a predetermined temp. A thermostat (24) selectively switches the power supply to the cooling unit (21) on and off, if the inner temp. of the sensor system is lower or higher than a predetermined critical temp. USE/ADVANTAGE - E.g. in semiconductor mfr. Facilitates stable control independent of environmental fluctuations esp. temp. fluctuations in surroundings.