CONDUCTIVITY SENSOR

• US 3,603,873 A
• Filed: 01/14/1970
• Issued: 09/07/1971
• Est. Priority Date: 01/14/1970
• Status: Expired due to Term

• Current Assignee: Uldis Cirulis
• Original Assignee: Uldis Cirulis
• Inventors: Cirulis, Uldis
• Primary Examiner(s): Lynch, Michael J.
• Application Number:
  US05/002,910
• Time in Patent Office: 601 Days
• Field of Search: 324/3R,3A,3B,65R
• US Class Current: 324/445
• CPC Class Codes: G01N 27/023 where the material is placed in the field of a coil

Abstract

A conductivity sensor having a fluid immersible, conductivity transformer comprised of a pair of toroidal cores on each of which are wound two windings, one of the windings on one core being the input winding, one of the windings on the other core being the output winding, the second winding on the input core providing a reference voltage and the second winding on the output core providing a means for negative feedback to null the flux in the second core. The output voltage and the reference voltages are compared to produce a measurement which is a function of the conductivity of the medium in which the conductivity transformer is immersed.

Claims

1. A conductivity sensor for measuring the conductivity of a fluid comprising:

a first toroidal core and a second toroidal core placed in juxtaposition and immersed in the fluid;

a first winding and a second winding wound on the first toroidal core;

a third winding and a fourth winding wound on the second toroidal core;

a source of alternating current connected to the first winding to thereby cause an alternating current to flow therein and to induce an alternating current in the second winding through inductive coupling in the first toroidal core and in the third winding through inductive coupling in the fluid;

first conversion means whose input is connected to the second winding so as to produce a reference voltage at the output of the first conversion means;

second conversion means whose input is connected to the third winding so as to produce an output voltage at the output of the second conversion means;

the fourth winding being connected to the output of an amplifier whose input is connected to the third winding so as to produce a negative feedback flux which eliminates the effect of the changes in the characteristics of the second toroidal core on the output voltage; and

comparison means for comparing the reference voltage and the output voltage to produce a signal which is a function of the conductivity of the fluid.

2. The invention of claim 1 including:

a resistor; and

wherein the amplifier is connected between the third winding and the second conversion means;

the resistor being connected in series with the output of the amplifier and the fourth winding.

3. The invention of claim 2 wherein the comparison means is a voltage to frequency converter having a frequency output which is proportional To the conductivity of the fluid.

4. The invention of claim 2 wherein the first conversion means is an absolute value amplifier.

5. The invention of claim 2 wherein the second conversion means is an absolute value amplifier.

6. The invention of claim 2 wherein the comparison means is a null detecting, voltage divider having a voltage output which is proportional to the conductivity of the fluid.

7. The invention of claim 1 wherein the first conversion means is an absolute value amplifier.

8. The invention of claim 1 wherein the second conversion means is an absolute value amplifier.

9. The invention of claim 1 wherein the comparison means is a null detecting, voltage divider having a voltage output which is proportional to the conductivity of the fluid.

10. The invention of claim 1 wherein the comparison means is a voltage to frequency converter having a frequency output which is proportional to the conductivity of the fluid.

11. The invention of claim 10 wherein the first conversion means and the second conversion means are absolute value amplifiers.

12. The invention of claim 9 wherein the first conversion means and the second conversion means are absolute value amplifiers.

13. The invention of claim 3 wherein the first conversion means and the second conversion means are absolute value amplifiers.

14. The invention of claim 6 wherein the first conversion means and the second conversion means are absolute value amplifiers.