Doppler measurement instrument and doppler measurement processing method

Patent metadata

Field	Value
Publication number	US-9625295-B2
Application number	US-201213569965-A
Country	US
Kind code	B2
Filing date	Aug 8, 2012
Priority date	Aug 8, 2011
Publication date	Apr 18, 2017
Grant date	Apr 18, 2017

Abstract

A fluid flow measurement instrument is provided. The measurement instrument includes a sensor producing a time domain signal representative of reflections of an emitted signal; and a meter being coupled to the sensor and configured to: receive the time domain signal; create two or more spectral estimates for the time domain signal, wherein said two or more spectral estimates have different frequency ranges and resolutions; determine a frequency offset value using one or more of the two or more spectral estimates; and convert the frequency offset value into a fluid velocity. Other aspects are described and claimed.

First claim

What is claimed is:

1. A fluid flow measurement instrument, comprising:
a sensor configured to measure a fluid flowing within a fluid channel, said sensor:
emitting a signal towards or into the fluid; and
producing a time domain signal representative of reflections of the emitted signal; and

a meter coupled to the sensor and comprising a processing system that is configured to:
receive the time domain signal;
successively decimate the time domain signal to generate a series of time domain decimated signal sets, wherein each successive decimation stage comprises a replica of a previous decimation stage and has an output sample rate lowered by a decimation factor;
thereafter compute a frequency transform for one or more of the series of time domain decimated signal sets, wherein each frequency transform provides a spectral quantification set having a different frequency resolution;
average spectral quantification sets associated with a frequency range to produce spectral estimates;
compute therefrom one or more frequency offset values; and
provide a fluid flow velocity estimate based upon the one or more frequency offset values so obtained.

2. The fluid flow measurement instrument of claim 1 , wherein the meter is configured to produce spectral estimates of differing frequency range and resolution,
wherein a spectral estimate on a particular analysis scale has the narrowest frequency range and the finest resolution; and
wherein spectral estimates on another analysis scale are obtained by processing more frames of time series data.

3. The fluid flow measurement instrument of claim 2 , wherein at all frequency resolution scales, a frequency transform of the same length is used.

4. The fluid flow measurement instrument of claim 2 , wherein the spectral estimates are used to form a zoomed centroid for determining a frequency offset value and computing therefrom the fluid flow velocity estimate.

5. The fluid flow instrument of claim 2 , wherein one or more of the spectral estimates are used to score another spectral estimate.

6. The fluid flow measurement instrument of claim 1 , wherein the meter is further configured to filter and window time domain decimated signal sets.

7. The fluid flow measurement instrument of claim 1 , wherein a spectral quantification set comprises a plurality of frequency bins.

8. The fluid flow measurement instrument of claim 1 , wherein the averaged spectral quantification sets comprise a plurality of spectral estimates that are processed to:
generate a spectral centroid from each spectral estimate, wherein each spectral centroid comprises an offset value for the corresponding spectral estimate; and
generate the frequency offset value from one or more spectral centroids.

9. The fluid flow measurement instrument of claim 1 , wherein the averaged spectral quantification sets comprise a plurality of spectral estimates that are processed to:
generate a zoomed centroid from the plurality of spectral estimates; and
generate the frequency offset value from the zoomed centroid.

10. The fluid flow measurement instrument of claim 1 , wherein to successively decimate comprises single-phase bandpass decimating of the time domain signal to produce a plurality of two-sided Doppler spectra.

11. A fluid flow measurement method, comprising:
emitting, from a sensor configured to measure a fluid flowing within a fluid channel, a signal towards or into the fluid;
producing a time domain signal representative of reflections of the emitted signal;
successively decimating the time domain signal to generate a series of time domain decimated signal sets, wherein each successive decimation stage comprises a replica of a previous decimation stage and has an output sample rate lowered by a decimation factor;
thereafter computing a frequency transform for one or more of the series of time domain decimated signal sets, wherein each frequency transform provides a spectral quantification set having a different frequency resolution;
averaging spectral quantification sets associated with a frequency range to produce spectral estimates;
computing therefrom one or more frequency offset values; and
providing a fluid flow velocity estimate based upon the one or more frequency offset values so obtained.

12. The fluid flow measurement method of claim 11 , further comprising operating the meter to:
produce spectral estimates of differing frequency range and resolution,
wherein a spectral estimate on a particular analysis scale has the narrowest frequency range and the finest resolution; and
wherein spectral estimates on another analysis scale are obtained by processing more frames of time series data.

13. The fluid flow measurement method of claim 12 , further comprising operating the meter to form a zoomed centroid using the spectral estimates;
wherein the zoomed centroid is used for determining a frequency offset value and computing therefrom the fluid flow velocity estimate.

14. The fluid flow measurement method of claim 11 , further comprising operating the meter to:
generate a spectral centroid from each spectral estimate, wherein each spectral centroid comprises an offset value for the corresponding spectral estimate; and
generate the frequency offset value from one or more spectral centroids.

15. A program product for fluid flow measurement, comprising:
a non-transitory, device readable program storage device storing device readable program code, the device readable program code being executable by a processor and comprising:
device readable program code configured to emit, from a sensor configured to measure a fluid flowing within a fluid channel, a signal towards or into the fluid;
device readable program code configured to produce a time domain signal representative of reflections of the emitted signal;
device readable program code configured to successively decimate the time domain signal to generate a series of time domain decimated signal sets, wherein each successive decimation stage comprises a replica of a previous decimation stage and has an output sample rate lowered by a decimation factor;
device readable program code configured to thereafter compute a frequency transform for one or more of the series of time domain decimated signal sets, wherein each frequency transform provides a spectral quantification set having a different frequency resolution;
device readable program code configured to average spectral quantification sets associated with a frequency range to produce spectral estimates;
device readable program code configured to compute therefrom one or more frequency offset values; and
device readable program code configured to provide a fluid flow velocity estimate based upon the one or more frequency offset values so obtained.

Assignees

• Rick David Langley
• Hach Co

Inventors

• Rick David Langley

Classifications

• G01F1/663 Primary

  by measuring Doppler frequency shift · CPC title

• G01F1/002

  wherein the flow is in an open channel · CPC title