Doppler measurement instrument and doppler measurement processing method

• US 9,625,295 B2
• Filed: 08/08/2012
• Issued: 04/18/2017
• Est. Priority Date: 08/08/2011
• Status: Active Grant

• Current Assignee: Hach Company (Veralto Corp.)
• Original Assignee: Hach Company (Veralto Corp.)
• Inventors: Rick, David Langley
• Primary Examiner(s): Charioui, Mohamed
• Assistant Examiner(s): Rastovski, Catherine
• Application Number:
  US13/569,965
• Publication Number:
  US 20130041600A1
• Time in Patent Office: 1,714 Days
• Field of Search: 702 45, 702 50, 702 51
• CPC Class Codes: G01F 1/002 wherein the flow is in an open channel
• CPC Class Codes: G01F 1/663 by measuring Doppler frequency shift

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.

Claims

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.