Envelope based sample correction for digital flow metrology

Patent metadata

Field	Value
Publication number	US-2016334250-A1
Application number	US-201514866779-A
Country	US
Kind code	A1
Filing date	Sep 25, 2015
Priority date	May 12, 2015
Publication date	Nov 17, 2016
Grant date	—

Abstract

A method of calculating a time difference is disclosed. The method includes receiving a first signal, determining a first envelope of the first signal, and determining a first time the first envelope crosses a threshold. The method further includes receiving a second signal, determining a second envelope of the second signal, and determining a second time the second envelope crosses the threshold. The time difference is calculated between the first and second times.

First claim

1 . A method, comprising:
receiving a first signal; determining a first envelope of the first signal; determining a first time the first envelope crosses a threshold; receiving a second signal; determining a second envelope of the second signal; determining a second time the second envelope crosses the threshold; and calculating a time difference between the first and second times.

2 . The method of claim 1 , wherein the step of calculating comprises:
determining a first difference between the first and second times; determining an absolute value of a time between the first difference and the time difference is not greater than a cycle time of the first signal; and adjusting the time difference by a cycle time if the absolute value is greater than a cycle time.

3 . The method of claim 1 , wherein the step of calculating comprises calculating a number of cycles of offset between the first and second signals.

4 . The method of claim 1 , comprising:
band pass filtering each of the first and second signals; squaring each of the first and second signals; low pass filtering each of the squared first and second signal; and calculating a respective square root of each of the filtered and squared first and second signals to determine their respective envelopes.

5 . The method of claim 1 , wherein the step of calculating comprises adjusting the time difference by interpolation.

6 . The method of claim 1 , wherein the step of calculating comprises aligning the first and second signals in response to the envelope threshold crossings.

7 . The method of claim 1 , wherein the step of calculating comprises cross correlating the first and second signals.

8 . The method of claim 1 , wherein the step of determining a first envelope comprises applying a Hilbert finite impulse response (FIR) transform to the first signal.

9 . The method of claim 1 , wherein the step of determining a first envelope comprises:
squaring the first signal to produce a squared first signal; low pass filtering the squared first signal; and calculating a square root of the low pass filtered and squared first signal.

10 . The method of claim 1 , comprising:
receiving the first signal from a first transducer at a second transducer; and receiving the second signal from a second transducer at the first transducer.

11 . The method of claim 1 , wherein the threshold comprises a variable threshold.

12 . The method of claim 1 , wherein the threshold comprises multiple thresholds.

13 . A method of calculating a time difference, comprising:
determining a first time from an envelope of a first signal; determining a second time from an envelope of a second signal; aligning the first and second signals in response to the first and second times; interpolating an alignment point of the first and second signals after the step of aligning; and calculating the time difference in response to the step of interpolating.

14 . The method of claim 13 , wherein the step of aligning comprises aligning a first cycle of the first signal with a first cycle of the second signal.

15 . The method of claim 13 , wherein the step of interpolating comprises calculating an offset adjustment after the step of aligning the first and second signals.

16 . The method of claim 13 , wherein the step of determining a first time comprises determining when the envelope of the first signal crosses a threshold.

17 . The method of claim 13 , wherein the step of calculating comprises:
determining a first difference between the first and second times; and determining an absolute value of a time between the first difference and the time difference is not greater than a cycle time of the first signal.

18 . A system for measuring material flow in a pipe, comprising:
a first transducer arranged to transmit a first signal having a first frequency at a first time and receive a second signal at a second time; a second transducer spaced apart from the first transducer and arranged to receive the first signal and transmit the second signal having the first frequency; and a processing circuit arranged to determine respective envelopes of the first and second signals and to calculate a flow rate in response to the respective envelopes.

19 . The system of claim 18 , wherein the processing circuit calculates a time difference between the first and second envelopes by comparing them to a threshold.

20 . The system of claim 18 , wherein the first transducer is affixed to a pipe, and wherein the second transducer is spaced apart from the first transducer and affixed to the pipe.

Assignees

• Texas Instruments Inc

Inventors

• Sathyanarayana Amardeep
• Dabak Anand G
• Magee David Patrick

Classifications

• G01F1/662 Primary

  Constructional details · CPC title

• G01F1/66 Primary

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