DETECTING METHOD AND APPARATUS USING HEAT SENSITIVE DEVICES

摘要

A fluid flow detecting system and method wherein a pair of electrically heated matched temperature sensitive devices (11, 12) are used to measure fluid flow. One of the devices (11) is placed in a position out of the fluid flow to be measured but in thermal relation to the fluid such that the device (11) is affected by variation in ambient temperature. The other device (12) is placed in the flowing fluid to be measured. Thus, a change in flow rate results in a change in the ratio of dissipation coefficients of the devices (11, 12). Circuitry (17, 45) is coupled to each of the devices (11, 12) for maintaining the two devices at substantially equal temperature. A change in the ratio of the power in the device (11, 12) with respect to each other indicates a change in the dissipation coefficient ratio which is insensitive to variation in ambient temperature.