Doppler radar flowmeter

• US 4,091,385 A
• Filed: 11/24/1976
• Issued: 05/23/1978
• Est. Priority Date: 11/24/1976
• Status: Expired due to Term

• Current Assignee: United States Department of Energy
• Original Assignee: United States Department of Energy
• Inventors: Sverdrup, Edward F., Petlevich, Walter J.
• Primary Examiner(s): Tubbesing, T.H.
• Application Number:
  US05/744,495
• Time in Patent Office: 545 Days
• Field of Search: 343/8, 343/17.7
• US Class Current: 342/115
• CPC Class Codes: G01F 1/663 by measuring Doppler frequency shift
• CPC Class Codes: G01S 13/58 Velocity or trajectory determination systems; Sense-of-movement determination systems

Abstract

A Doppler radar flowmeter comprises a transceiver which produces an audio frequency output related to the Doppler shift in frequency between radio waves backscattered from particulate matter carried in a fluid and the radiated radio waves. A variable gain amplifier and low pass filter are provided for amplifying and filtering the transceiver output. A frequency counter having a variable triggering level is also provided to determine the magnitude of the Doppler shift. A calibration method is disclosed wherein the amplifier gain and frequency counter trigger level are adjusted to achieve plateaus in the output of the frequency counter and thereby allow calibration without the necessity of being able to visually observe the flow.

Claims

1. A Doppler radar flowmeter for measuring the velocity of flow of particulate matter carried by a fluid within a conduit comprising:

transceiver means for radiating radio waves at a predetermined microwave frequency through a microwave window in said conduit and at least partially through said fluid, and for receiving at least a portion of said radio waves back-scattered by at least a portion of said particulate matter in the path of said radiated radio waves;

means connected to said transceiver means including a variable gain amplifying means for producing a signal of variable amplitude related to the Doppler shift in frequency between said back-scattered radio waves and said radiated radio waves, and thus related to the velocity of flow of the particulate matter;

frequency counting means responsive solely to peaks in said signal which have an amplitude greater than a variable trigger level of said counter means, for measuring the frequency of said signal;

wherein said variable gain amplifying means and said variable trigger level of said counter provide calibration means for said flowmeter.

2. The flowmeter of claim 1 further comprising low pass filter means for filtering said signal to remove frequency components therefrom having a frequency greater than a predetermined value.

3. The flowmeter of claim 1 wherein said radiating and receiving means comprise at least one antenna which is movable, such that the distance of said at least one antenna from the fluid may be adjusted to maximize the strength of said back-scattered radio waves received by said receiving means.

4. A method for calibrating a flowmeter, said flowmeter comprising:

means for radiating radio waves at a predetermined microwave frequency at least partially through the fluid, and for receiving at least a portion of the radio waves back-scattered by at least a portion of the particulate matter in the path of said radiated radio waves;

means connected to said receiving means for producing a signal related to the Doppler shift in frequency between said back-scattered radio waves and said radiated radio waves, and thus related to the velocity of flow of the particulate matter;

frequency counting means responsive solely to peaks in said signal which have an amplitude greater than a variable trigger level of said counter means, for measuring the frequency of said signal;

variable gain amplifying means for varying the amplitude of said signal, wherein said calibration method comprises the steps of;

adjusting the gain of said amplifying means such that the output signal thereof has a predetermined peak value;

adjusting the triggering level of said frequency counting means by increasing the level from a first level where said frequency counting means is responsive to peaks in said amplifier output signal caused by noise, to a second level corresponding to the plateau in the output of said frequency counting means where the variation in the output of said frequency counting means with respect to increases in the triggering level is at a minimum;

readjusting the gain of said amplifying means by increasing the gain from a first level where said frequency counting means is only partially responsive to fluctuations in said signal attributable to said Doppler shift, to a second level corresponding to the first plateau in the output of said frequency counting means where variation in the output of said frequency counting means with respect to increases in the gain of said amplifying means is at a minimum.

5. The calibration method of claim 4 further comprising the step of:

readjusting the trigger level of said frequency counting means by increasing the level from a third level where said frequency counting means is responsive to peaks in said signal caused by noise, to a fourth level corresponding to the plateau in the output of said frequency counting means where the variation in the output of said frequency counting means with respect to increases in the triggering level is at a minimum.