Thermal flow meter control method

摘要

A thermal flow meter corrects flow rate detection errors produced by vaporization of liquid phase components included in a gas to be measured. The thermal flow meter includes a correction circuit 500 that applies respectively different predetermined voltages to heating resistors consisting of first heating resistor Rh1 and second heating resistor Rh2 of a sensor element disposed in the gas to be measured to set a first temperature state and a second temperature state, calculates a first flow rate value Q1 of the gas to be measured in the first temperature state and a second flow rate value Q2 of the gas to be measured in the second temperature state, and calculates a flow rate correction value ”Q based on a ratio (Q1/Q2) between the first flow rate value and second flow rate value or a fourth-power value (Q1/Q2) 4 of the ratio to correct a flow rate of the gas to be measured.