Flow detection with quadrature demodulation

Patent metadata

Field	Value
Publication number	US-10727787-B2
Application number	US-201715705961-A
Country	US
Kind code	B2
Filing date	Sep 15, 2017
Priority date	Sep 15, 2017
Publication date	Jul 28, 2020
Grant date	Jul 28, 2020

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.

First claim

What is claimed is:

1. A method of measuring flow rate comprising:
generating an upstream signal for transmission through a fluid whose flow rate is being measured;
receiving the upstream signal and converting the upstream signal to a first upstream digital representation and storing the first upstream digital representation as a stored first upstream digital representation;
generating a downstream signal for transmission through the fluid whose flow rate is being measured;
receiving the downstream signal and converting the downstream signal to a first downstream digital representation and storing the first downstream digital representation as a stored first downstream digital representation;
performing one or more multi-pass algorithms on the stored first upstream digital representation and the stored first downstream digital representation and generating a processed first upstream digital representation and a processed first downstream digital representation;
performing quadrature demodulation of the processed first upstream digital representation and determining an upstream angle associated therewith;
performing quadrature demodulation of the processed first downstream digital representation and determining a downstream angle associated therewith; and
determining the flow rate based in part on an angle difference between the upstream angle and the downstream angle.

2. The method as recited in claim 1 wherein the one or more multi-pass algorithms is at least one of a time domain window function and an amplitude equalization function.

3. The method as recited in claim 2 wherein performing the one or more multi-pass algorithms comprises:
determining the time domain window function based, at least in part, on the first stored upstream digital representation and one or more of the first stored downstream digital representation and a second stored upstream digital representation corresponding to a second upstream signal transmitted through the fluid.

4. The method as recited in claim 2 wherein performing the one or more multi-pass algorithms comprises:
equalizing amplitudes of the first stored upstream digital representation and one or more of the first stored downstream digital representation and a second stored upstream digital representation corresponding to a second upstream signal transmitted through the fluid.

5. The method as recited in claim 2 wherein the time domain window function is a smoothing window function.

6. The method as recited in claim 1 further comprising:
wherein the quadrature demodulation correlates the upstream and downstream signals with in-phase and quadrature sinusoids that are at a frequency of the upstream signal and the downstream signal.

7. The method as recited in claim 1 wherein the upstream signal is a programmable sinusoidal burst exponentially increasing and exponentially decaying to zero.

8. The method as recited in claim 1 further comprising programming a frequency of the upstream signal and the downstream signal to match a respective resonant frequencies of piezo-electric transducers coupled to a pipe in which the fluid flows.

9. The method as recited in claim 1 further comprising:
programming one or more of an amplitude of the upstream signal, a number of cycles in the upstream signal, and a pulse shape of the upstream signal.

10. The method as recited in claim 1 further comprising:
resolving ambiguity associated with a difference between the upstream angle and the downstream angle using a first coarse time of flight measurement of the upstream signal and a second coarse time of flight measurement of the downstream signal.

11. The method as recited in claim 1 further comprising:
if the upstream angle is smaller than the downstream angle, adding 2π to the upstream angle as part of determining the angle difference.

12. An apparatus comprising:
a transmitter for generating an upstream signal and a downstream signal for transmission through a fluid whose flow rate is being measured;
a receiver configured to receive the upstream signal and the downstream signal, the receiver including,
an analog to digital converter to convert the upstream signal to an upstream digital representation and to convert the downstream signal to a downstream digital representation;
a quadrature demodulator configured to multiply the upstream signal after conversion in the analog to digital converter with an in-phase sinusoid and a quadrature sinusoid that are equal in frequency to the upstream signal and to thereby generate in-phase and quadrature components associated with the upstream signal;
the quadrature demodulator being further configured to multiply the downstream signal after conversion in the analog to digital converter with in-phase and quadrature sinusoids that are equal in frequency to the downstream signal to thereby generate in-phase and quadrature components associated with the downstream signal;
wherein an upstream angle is determined based on the in-phase and quadrature components associated with the upstream signal and a downstream angle is determined based on the in-phase and quadrature components associated with the downstream signal; and
wherein the apparatus is configured to determine a flow rate of the fluid based in part on an angle difference between the upstream angle and the downstream angle.

13. The apparatus as recited in claim 12 further comprising:
at least one integrate and dump filter to integrate the one or more of the in-phase and quadrature components of the downstream digital representation and the one or more of the in-phase and quadrature components of the downstream digital representation and supply an integrated upstream in-phase value, an integrated upstream quadrature value, an integrated downstream in-phase value and an integrated downstream quadrature value; and
an arctangent function to determine the upstream angle based on the integrated upstream in-phase value and the integrated upstream quadrature value and to determine the downstream angle based on the integrated downstream in-phase value and the integrated downstream quadrature value.

14. The apparatus as recited in claim 12 wherein the receiver further comprises:
a smoothing time domain windowing filter to exclude digital samples in the upstream digital representation prior to demodulation, the smoothing time domain windowing filter based on the upstream digital representation and at least one of the downstream digital representation and a second upstream digital representation of a second upstream signal.

15. The apparatus as recited in claim 12 wherein the receiver further comprises:
an amplitude equalizing function to equalize amplitudes of the upstream digital representation and at least one of the downstream digital representation and a second upstream digital representation of a second upstream signal.

16. The apparatus as recited in claim 12 further comprising:
wherein a frequency of the downstream signal is programmed to match a resonant frequency of a piezo-electric transducer supplying the downstream signal to the fluid.

17. The apparatus as recited in claim 12 wherein the transmitter further comprises:
memory to store a digital representation of the downstream signal to be transmitted;
a digital to analog converter to convert the digital representation of the downstream signal to be transmitted to an analog representation; and
wherein an amplitude of the upstream signal, a number of cycles of the upstream signal, and a pulse shape of the upstream signal are programmable.

18. The

Assignees

• Silicon Lab Inc

Inventors

• Khoury John M

Classifications

• H03D3/007 Primary

  by converting the oscillations into two quadrature related signals (H03D3/245 takes precedence) · CPC title

• G01F1/667

  Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters · CPC title

• G01F1/66

  by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters · CPC title

• H03D2200/0082

  Quadrature arrangements · CPC title

• H03D3/009 Primary

  Compensating quadrature phase or amplitude imbalances · CPC title