NON-OBSTRUCTIVE THERMODYNAMIC FLOW METER

摘要

A fluid flow meter using a pair of temperature-variable resistance elements as detectors. Both elements are exposed to the fluid flow and supplied with a series of current pulses. The pulses supplied to one element, the reference element, are of very short duration so as to have no appreciable heating effect; the pulses supplied to the other element are of longer duration and are controlled so as to maintain this element at a fixed temperature differential above the other element, which remains at fluid temperature. The pulse width of the longer duration pulses is a measure of the flow rate of the fluid. Since the relationship between heat dissipated in the element and fluid flow varies with fluid temperature, the voltage pulses across the reference element are used as a measure of fluid temperature to compensate for this variation in calculating the exact fluid flow rate.