THERMAL FLOW-RATE SENSOR AND THERMAL FLOW-RATE DETECTION CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a circuit where the influence of the reduction in a detection accuracy is reduced after the aging of the resistance of a resistor affects the flow-rate detection accuracy in a thermal flow-rate detection circuit where the resistor being heated by a heater detects the degree of cooling by a fluid according to the change in the resistance of the resistor due to the temperature for detecting the flow or the flow rate of the fluid. SOLUTION: Although current flowing to a heater R7 being connected to a constant-temperature control circuit 41 that is constituted so that the voltage difference between a thermally sensitive resistor R1 and a fluid temperature detection thermally sensitive resistor R6 becomes constant has been detected according to the voltage across both the ends of the heater R7 conventionally, a fixed resistor R4 is inserted in series with R7 for extracting a signal voltage V10 from both the ends of the fixed resistor R4 this time.