Process and device for measuring the flow rate of a fluid

Claim 1

Flowmeter for a fluid, comprising a length of pipeline through which the fluid flows, emitting means constituted by an electrical resistance in the form of a grid extending in a transverse plane of the length of pipeline for producing, in response to an input pulse, a disturbance to the state of the fluid positioned in the pipeline at a first point in its length, a detector constituted by an electrical resistance having a temperature coefficient and supplied with a constant current, said detector being sensitive to the disturbance in the state of the fluid for emitting an output signal, the detector being positioned in the pipeline at a second point in its length spaced downstream of said first point in the direction of flow by a predetermined distance, a pulse generator for periodically applying an input pulse to said emitting means, and means connected to said pulse generator and to said detector for measuring the time between an input pulse and the corresponding output signal, said means for measuring the time comprising an amplifier having an input connected to the terminals of the resistance having a temperature coefficient by way of a first capacitor, a flip-flop with an enabling input connected to the pulse generator and a disabling input connected to the output of the amplifier, and a second capacitor which is charged in response to the pulses from the generator and is discharged across a resistance by the enabled flip-flop.