Silicon Laboratories Inc.
Flow detection with quadrature demodulation

Abstract:

A transmitter generates programmable upstream and downstream signal pulses for transmission through a fluid whose flow rate is being measured. A receiver receives the upstream and downstream signal pulses and stores digital representations of the pulses. A multiple pass algorithm such as a time domain windowing function and/or an algorithm that equalizes amplitude operates on the stored digital representations prior to demodulation. A quadrature demodulator generates in-phase and quadrature components of the digital representations and an arctangent function using the in-phase and quadrature components determines angles associated with the upstream and downstream signal pulses. The difference between the upstream and downstream angles, from which a difference in time of flight between the upstream and downstream signal pulses can be derived, is used to determine flow rate.