Air flow meter of thermal resistance type for measuring air flow rate

摘要

The output electronic circuits (101,102) process the input signal, derived from passing a constant current through the thermal resistance (1), to produce an air rate signal. The circuit uses differential amplifier circuits and associated resistors, which are used for determining the amplification factor of the circuit. The temperature sensitive resistance (2) is located in the air duct (30) with the thermal resistance, and is connected in series with a resistance (10) in an amplifier (8) feedback circuit. The output circuit includes a unit for correcting the air flow rate indication related to the temp. alteration, using at least one resistor of a type with a temp. coefficient which differs from the resistors provided otherwise, to correct the variation of circuit performance.