Wave shape chemical analysis apparatus and method

• US 4,679,426 A
• Filed: 09/09/1985
• Issued: 07/14/1987
• Est. Priority Date: 09/09/1985
• Status: Expired due to Term

• Current Assignee: Solid State Farms Incorporated
• Original Assignee: Solid State Farms Incorporated
• Inventors: Fuller, Milton E., Fletcher, Gary S. Jr.
• Primary Examiner(s): Levy, Stewart J.
• Assistant Examiner(s): Roskos, Joseph W.
• Application Number:
  US06/774,150
• Time in Patent Office: 673 Days
• Field of Search: 73/53, 73/61 R, 73/61.1 R, 73/590
• US Class Current: 73/53.01
• CPC Class Codes: G01N 22/00 Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more G01N3/00 - G01N17/00, G01N24/00 take precedence

Abstract

An apparatus and method for measuring the concentration of a chemical substance in a test sample based on a technique of waveform distortion analysis is disclosed. The apparatus includes a waveform generator that generates a periodic signal, an antenna probe that transmits the signal into the test sample and receives from the test sample a corresponding periodic signal, the waveform of which has been distorted or otherwise transformed by the chemical, and a detector circuit that quantifies the transformation of the signal to determine the concentration of the chemical in the test sample. The waveform shape and frequency are selected so that the transformation is particularly responsive to the presence of a selected chemical substance, so that the magnitude of the distortion or transformation of the signal is directly related to the concentration of the selected chemical substance.

Claims

1. An apparatus for measuring the concentration of a chemical in a test sample, said apparatus comprising:

electromagnetic waveform generation means for generating an electromagnetic signal having a periodic waveform of known shape;

antenna means coupled to said waveform generation means for transmitting said electromagnetic signal into the test sample and for receiving a corresponding periodic electromagnetic signal having a waveform with a shape changed from said known shape as a result of propagation of said electromagnetic signal through the test sample; and

detection means coupled to said antenna means and responsive to the transmitted and received electromagnetic signals for quantifying the change in shape of said received electromagnetic signal with respect to said known shape of said transmitted electromagnetic signal, said detection means further being formed to determine the concentration of the chemical in the test sample by correlation of the magnitude of the change in shape relative to a known concentration of the chemical from calibration test samples.

2. An apparatus as recited in claim 1 wherein,

said waveform generation means is operable for generating an electromagnetic signal having a shape and frequency selected with reference to the chemical for which concentration is to be measured in order to enhance the magnitude of said change in shape.

3. An apparatus as recited in claim 2 wherein, said waveform generation means includes a square wave oscillator.

4. An apparatus as recited in claim 1 wherein,

said antenna means includes two conductive prongs protruding from a housing with one of said prongs being operable for transmitting said electromagnetic signal into the test sample and the other one of said prongs being operable for receiving said electromagnetic signal from the test sample;

and

each of said prongs further being generally cylindrical in shape and including a solid end that protrudes from said housing for insertion into the test sample, said prongs further being formed with a hollow cavity disposed opposite said solid end for receiving an electrical conductor for connection to at least one of said waveform generation means and said detection means.

5. An appartus as recited in claim 1 wherein,

said detection means includes summing means for generating a reference signal having a periodic waveform by combining said transmitted electromagnetic signal and said received electromagnetic signals, and said detection means includes signal processing means coupled to receive said transmitted electromagnetic signal, said received electromagnetic signal, and said reference signal for generating an output signal related to the concentration of the chemical in the test sample by multiplying the voltage differential between said transmitted electromagnetic signal and said reference signal by the voltage differential between said received electromagnetic signal and said reference signal.

6. An apparatus as recited in claim 5 wherein, said detection means further includes output means responsive to said output signal for displaying an indication of the concentration of the chemical in the test sample.

7. An apparatus as recited in claim 1 wherein, said waveform generation means is isolated from said antenna means by a capacitor to prevent direct current flow through the test sample.

8. An apparatus as recited in claim 1 wherein, said detection means is isolated from said antenna means by a capacitor to prevent direct current flow through the test sample.

9. An apparatus for measuring the concentration of sodium chloride in a test sample, said apparatus comprising:

waveform generation means for generating an electromagnetic signal having a periodic substantially square waveform and a frequency selected with reference to sodium chloride in order to enhance the magnitude of the change in shape of said waveform during propagation in the test sample;

antenna means coupled to said waveform generation means for transmitting said electromagnetic signal into the test sample and for receiving a corresponding periodic electromagnetic signal from the test sample, wherein the waveform of said electromagnetic signal is changed in shape by said sodium chloride as said electromagnetic signal propagates through the test sample; and

detection means responsive to the transmitted and received electromagnetic signals for quantifying the change in shape of said electromagnetic received signal with respect to said transmitted electromagnetic signal to determine the concentration of sodium chloride in the test sample, wherein the magnitude of the change of shape is related to the concentration of sodium chloride in the test sample.

10. An apparatus for measuring the concentration of sodium chloride as recited in claim 9, wherein, said transmitted electromagnetic signal has a frequency of between fifteen and nineteen megahertz.

11. An apparatus for measuring the concentration of sodium chloride as recited in claim 10 wherein,

said transmitted electromagnetic signal has a frequency substantially equal to sixteen megahertz.

12. An apparatus for measuring the concentration of sodium chloride as recited in claim 10 wherein,

said transmitted electromagnetic signal has a frequency substantially equal to eighteen megahertz.

13. An apparatus for measuring the presence of a chemical in a test sample, said apparatus comprising:

electromagnetic signal generation means formed for generating an electromagnetic signal having a periodic waveform and a shape and frequency selected with reference to the chemical to be measured;

electromagnetic signal transmission means coupled to said electromagnetic signal generation means for transmitting said electromagnetic signal into the test sample;

electromagnetic signal receiving means spaced apart from said transmission means for receiving said electromagnetic signal after it has propagated through the test sample for distortion of the shape of said electromagnetic signal upon the presence of the chemical in the test sample; and

detection means responsive to the transmitted and received electromagnetic signals for detecting the distortion of the shape of said electromagnetic signal upon the presence of the chemical in the test sample and indicating the presence of the chemical upon detecting distortion of the shape of said electromagnetic signal.

14. A method for detecting the presence of a chemical in a test sample, said method comprising the steps of:

generating an electromagnetic signal having a periodic waveform and transmitting said electromagnetic signal through a portion of the test sample;

receiving said electromagnetic signal after it has passed through the test sample; and

detecting any change in shape of said electromagnetic signal, as a result of passing through the test sample and correlating said transformation of the shape to the presence of the chemical in the test sample.

15. A method as recited in claim 14 wherein, said step of generating an electromagnetic signal includes the step of generating an electromagnetic signal having a shape and frequency selected with reference to the chemical to be measured in order to enhance the magnitude of the transformation.

16. A method as recited in claim 14 wherein,

said step of detecting the change in shape of said electromagnetic signal includes the steps of generating a reference signal having a periodic waveform by combining said transmitted and received electromagnetic signals, and generating an output signal related to the concentration of the chemical in the test sample by multiplying the voltage differential between said transmitted and reference electromagnetic signals by the voltage differential between said received electromagnetic signal and said reference signal.

17. A method for tuning an apparatus for measuring the concentration of a chemical in a test sample, wherein said apparatus includes electromagnetic waveform generation means for generating an electromagnetic signal having a periodic waveform of known shape, includes antenna means coupled to the waveform generation means for transmitting the electromagnetic signal into the test sample and for receiving from the test sample a periodic electromagnetic signal having a changed shape from said known shape that results from the electromagnetic signal propagating through the test sample, and includes detection means responsive to the transmitted and received electromagnetic signals for quantifying the change in shape of the electromagnetic signal, said method comprising the steps of:

inserting the antenna means into a test sample containing a representative amount of the chemical;

monitoring the amount of change in shape of the received electromagnetic signal with respect to the transmitted electromagnetic signal while varying the frequency of the transmitted electromagnetic signal through a range of frequencies;

selecting for use as the frequency of the transmitted electromagnetic signal in using the apparatus to measure the concentration of the chemical that frequency which causes the greatest amount of change in shape of the signal due to the presence of the chemical in the test sample; and

monitoring the amount of change of shape of the received electromagnetic signal with respect to the transmitted electromagnetic signal while varying the waveform shape of the transmitted electromagnetic signal, and selecting for use as the waveform shape of the transmitted electromagnetic signal in using the apparatus to measure the concentration of the chemical that waveform shape which causes the greatest amount of change of shape of the electromagnetic signal due to the presence of the chemical in the test sample.

18. A method for measuring the concentration of sodium chloride in a test sample comprising the steps of:

generating an electromagnetic signal having a periodic waveform of known shape and a frequency of between about fifteen and nineteen megahertz;

transmitting said electromagnetic signal through a portion of said test sample;

receiving said electromagnetic signal after it has passed through said test sample;

detecting changes in shape of the received electromagnetic signal as compared to said known shape; and

quantifying said changes in shape and correlating the quantified changes in shape with a concentration of sodium chloride.

19. A method for measuring the concentration of sodium chloride in a test sample, as recited in claim 18 wherein, said step of generating an electromagnetic signal includes the step of generating an electromagnetic signal having a substantially square shape.

20. A method as recited in claim 18 wherein, said signal has a frequency substantially equal to sixteen megahertz.

21. A method as recited in claim 18 wherein, said electromagnetic signal has a frequency substantially equal to eighteen megahertz.