Fluid flow rate detector using temperature sensors

摘要

The fluid flowmeter comprises a flow channel (14) within which a heated first and an unheated second temperature sensor (20, 22), i.e. thermistors, are positioned, the second downstream from the first. A differential amplifier (47) is fed by the voltages (Va, Vb) of both thermistors and determines a differential voltage (Vc) between them corresponding to the speed of flow. This signal is transmitted through an A/D converter (50) to a central processor (48) for calculation of flow rate based on the speed and on the diameter of the channel. The actual flow rate can be automatically compared with thresholds previously entered into the processor memory (52) so that a corresponding signal is transmitted to transistors (54a, b) which switch on or off a controlling charge (58a, 58b) to external equipment as appropriate.