MEASUREMENT OF FLUID TEMPERATURE BY THERMAL FLOWMETER

摘要

PURPOSE:To enable a fluid temperature signal and a flow rate signal to be obtained at the same time without changing the constitution of a bridge circuit by constituting it by a heating resistor, a temperature compensating resistor and a fixed resistor. CONSTITUTION:A heating resistor 2 composed of a temperature dependent resistor and a temperature compensating resistor 3 for detecting a fluid temperature are arranged in a passage 1. The resistor 2 and a fixed resistor 6 are connected between the output end A1 of a current supplying amplifier 7 and the ground in series and a series circuit comprising the resistor 3 and fixed resistors 4 and 5 is also connected between the output end A1 and the ground, constituting a bridge circuit. The junction C of the resistors 4 and 5 and the junction B1 of the resistors 6 and 2 are connected to the input end of the amplifier 7. Electric power is supplied to the amplifier 7 from a power supply 7. Flow rate detecting signals 10 and heating resistance value detecting signals are detected at the two points of the bridge circuit. Those signals are A/D- converted, taken-in by a microcomputer and arithmetically processed therein whereby a flow rate can be measured and, at the same time, a fluid temperature can be also detected.