Flow rate meter with temperature dependent resistor

摘要

A flow rate meter for measuring the flow rate of a fluid medium, especially that of the air aspirated by an internal combustion engine. A hot wire or film is placed in the air stream and is made part of an electrical circuit powered by the output of a differential amplifier. The voltage drop across the resistor is monitored at the input of the differential amplifier where it is compared with fixed or compensated values. In order to reduce the effect that airborne particles, which are deposited on the hot wire or film, have on the measuring characteristics of the apparatus, the wire or film are shaped so that their leading edge constitutes an area much smaller than the surfaces which are substantially parallel to the stream lines.