Thermal flow meter, thermal gas species discrimination apparatus and gas species automatic determination method

摘要

PROBLEM TO BE SOLVED: To provide a thermal-type flowmeter and a method of automatic determination of a gas type which automatically determines the type of gas inside a channel, corrects gas flow rate with a correction value specified by the gas and which thereby detects the gas flow rate with high accuracy.;SOLUTION: The thermal-type flowmeter includes: a thermal-type sensor 14 which is disposed in the channel 11, making the gas flow in the vertical direction and outputs a detection signal showing the difference between temperatures detected by an upstream-side temperature measuring resistance element 45 and a downstream-side temperature measuring resistance element 46; a pressure sensor 15 which detects pressure in the channel 11; a gas determining part 52, which determines the type of gas from the relation between a stop time detection signal outputted by the thermal-type sensor 14, at stoppage of the supply of the gas and the stop time pressure detected by the pressure sensor 15; a corrective value deciding part 53 which decides the corrective value for correcting a change in the sensor output characteristics of the thermal-type sensor 14, according to the determined type of the gas; and a flow rate calculating part 54 which corrects the detection signal of the thermal-type sensor 14 with the corrective value and calculates the flow rate of the gas flowing through the channel 11.;COPYRIGHT: (C)2012,JPO&INPIT