Liquid conductivity measuring device

• US 3,992,662 A
• Filed: 08/16/1974
• Issued: 11/16/1976
• Est. Priority Date: 08/16/1974
• Status: Expired due to Term

• Current Assignee: Billy D. Etherton, Eugene P. Ziner, Russell J. Horn, William E. Berry
• Original Assignee: Billy D. Etherton, Eugene P. Ziner, Russell J. Horn, William E. Berry
• Inventors: Koepnick, Glenn, Balzen, Richard T., Etherton, Billy D.
• Primary Examiner(s): Rolinec, R. V.
• Assistant Examiner(s): Tokar, Michael J.
• Application Number:
  US05/498,192
• Time in Patent Office: 823 Days
• Field of Search: 324/30 R, 324/30 B, 324/189, 324/30 A, 307/294
• US Class Current: 324/442
• CPC Class Codes: G01N 27/045 Circuits measuring resistance per se G01R27/00, e.g. G01R27/22
• CPC Class Codes: G01N 27/06 of a liquid involving electrolysis G01N27/26
• CPC Class Codes: G01R 27/22 Measuring resistance of fluids

Abstract

A portable device for measuring the conductivity of a liquid between two probes spaced relative to each other along the lateral axis of a container. The gains of a plurality of operational amplifiers are varied for range, by conductivity and by temperature variations to provide a signal representative of the conductivity of the liquid. An oscillator using two operational amplifiers is used to drive the measuring amplifier.

Claims

1. An apparatus for measuring the conductivity of liquids comprising:

means for producing an oscillating output signal;

range means, connected to the output of said oscillator means, for varying the amplitude of said output signal of said oscillator means, said range means includes a range operational amplifier, a plurality of resistors connected between the output of said oscillator means and the input of said range amplifier and a plurality of switches connected across said resistors so that selected resistors may be added or removed from the input resistance of said range amplifier and said plurality of resistors is three and said plurality of switches is two, one switch is connected in parallel with a first resistor and the other switch is connected in parallel with said first resistor and a second resistor;

two probes to be placed in contact with the liquid, whose conductivity is to be measured, one of said probes being connected to the output of said range means;

amplifier means, connected to the other of said probes, whose gain varies in response to the conductivity of said liquid; and

an indicator means connected to the output of said amplifier means for indicating said liquid'"'"'s conductivity.

2. An apparatus for measuring the conductivity of liquids comprising:

means for producing an oscillating output signal including a first and second operational amplifier, said first amplifier'"'"'s output being connected to an input of said second amplifier through an RC circuit, and gain means connected to both of said amplifiers for varying the gain of said first amplifier in response to the output of said second amplifier, the output of said first amplifier is the output of said oscillator means;

range means connected to the output of said oscillator means for varying the amplitude of said output signal of said oscillator means;

measuring means comprised of two probes to be placed in contact with the liquid, whose conductivity is to be measured, one of said probes being connected to the output of said range means and including a temperature responsive means connected to said measuring means and mounted directly to one of said probes exterior to the inner surface of said container means and within said housing, said one of said probes transmitting the temperature of a liquid in said container means to said temperature responsive means;

amplifier means, connected to the other of said probes, whose gain varies in response to the conductivity of said liquid; and

an indicator means connected to the output of said amplifier means for indicating said liquid'"'"'s conductivity.

3. An apparatus for measuring the conductivity of liquid comprising:

means for producing an oscillating output signal;

range means connected to the output of said oscillator means for varying the amplitude of said output signal of said oscillator means, said range means includes a range operational amplifier, a plurality of resistors connected in series between the output of said oscillator means and the input of said range amplifier and a plurality of switches connected across said resistors so that selected resistors may be added or removed from the input resistance of said range amplifier;

two probes to be placed in contact with the liquid, whose conductivity is to be measured, one of said probes being connected to the output of said range means;

amplifier means, connected to the other of said probes, whose gain varies in response to the conductivity of said liquid; and

an indicator means connected to the output of said amplifier means for indicating said liquid'"'"'s conductivity.

4. An apparatus for measuring the conductivity of liquids comprising:

means for producing an oscillating output signal;

range means connected to the output of said oscillator means for varying the amplitude of said output signal of said oscillator means;

two probes to be placed in contact with the liquid, whose conductivity is to be measured, one of said probes being connected to the output of said range means;

amplifier means, connected to the other of said probes, whose gain varies in response to the conductivity of said liquid;

an indicator means connected to the output of said amplifier means for indicating said liquid'"'"'s conductivity; and

first switch means connected to said indicator means, said first switch means selectively interconnecting said indicator means to one member of the group consisting of said oscillator means for calibration and said amplifier means for reading the conductivity of said liquid on said indicator means, and an open circuit.

5. The apparatus of claim 4 including power switch means connecting said power source to the elements of the apparatus, said power switch means and said first switch means being three position toggle switches and being mechanically ganged so that the power source is connected to the elements of the apparatus by said power switch when said first switch means if selectively positioned either for calibrating or reading conductivity and said power switch means is open when said first switch means is open.

6. An apparatus for measuring the conductivity of liquids comprising:

means for producing an oscillating output signal;

range means connected to the output of said oscillator means for varying the amplitude of said output signal of said oscillator means;

a container having an opening in the top thereof for holding the liquid whose conductivity is to be measured;

two probes displaced along the vertical axis of said container relative to each other one of said probes being connected to the output of said range means;

amplifier means connected to the other of said probes;

means responsive to the temperature of said liquid connected to said amplifier means and mounted directly to one of said probes, said probe transferring the temperature of said liquid to said temperature responsive means;

the gain of said amplifier means varies in response to the conductivity of said liquid and said temperature responsive means; and

an indicator means connected to the output of said amplifier means for indicating said liquid'"'"'s conductivity.

7. An apparatus for measuring the conductivity of liquids comprising:

means for producing an oscillating output signal including a first and second operational amplifier, said first amplifier'"'"'s output being connected to an input of said second amplifier through an RC circuit, and gain means connected to both of said amplifiers for varying the gain of said first amplifier in response to the output of said second amplifier, the output of said first amplifier is the output of said oscillator means;

range means connected to the output of said oscillator means for varying the amplitude of said output signal of said oscillator means;

two probes to be placed in contact with the liquid, whose conductivity is to be measured, one of said probes being connected to the output of said range means;

amplifier means, connected to the other of said probes, whose gain varies in response to the conductivity of said liquid; and

an indicator means connected to the output of said amplifier means for indicating said liquid'"'"'s conductivity.

8. The apparatus of claim 7 wherein said second amplifier operates at either its upper or lower saturation states and said RC circuit cause said second amplifier to switch between its saturation states periodically.

9. The apparatus of claim 7 wherein said gain means includes a pair of diodes and a resistor, one diode is connected to a common junction and the output of said second amplifier and the other diode is connected in series with said resistor between said common junction and an input to said first amplifier so that only one of said diodes at a time is conducting and said resistor varies the input resistance of said first amplifier.

10. The apparatus of claim 8 wherein said periodic switching has a 50% duty cycle and said first amplifier operates without saturating.

11. A device for indicating conductivity of a liquid comprising:

a housing;

a container means being an integrally formed portion of said housing for receiving said liquid, said container means having an opening in its top for entry of said liquid;

a pair of probes in said container means displaced from each other along the vertical axis of said container means and forming a portion of the interior surface of said container means;

means in said housing for measuring the conductivity of a liquid contacting both probes and providing a signal representative of said conductivity; and

an indicator in said housing and connected to said means measuring for displaying the conductivity of said liquid.

12. The device of claim 11 wherein said housing is less than 18 cubic inches in volume and said device includes a power source within said housing.