FLOW RATE MEASURING INSTRUMENT

摘要

A bridge circuit (1) includes a heating resistor (RH), a reference resistor (RR), and a pair of fixed resistors (R1, R2), one of which is series-connected to the heating resistor and the other series-connected to the reference resistor. Drive voltage for the bridge circuit (1) is controlled to bring the bridge circuit (1) to equilibrium. Ambient temperature (TQ) affecting the reference resistor is calculated on the basis of the drive voltage for this bridge circuit and bridge output voltage thereof. Flow rate obtained by a sensor body is corrected on the basis of this ambient temperature and a rate of change of the sensor body per unit temperature ( DELTA P) corresponding to the flow rate. Thus, the flow rate of fluid is measured with high accuracy, without being affected by the ambient temperature or the flow rate.