Method and apparatus for measuring chemical concentration in a fluid

• US 20040178802A1
• Filed: 03/14/2003
• Published: 09/16/2004
• Est. Priority Date: 03/14/2003
• Status: Active Grant

• Current Assignee: Steris Corporation
• Original Assignee: Steris Corporation
• Inventors: Centanni, Michael A.
• Granted Patent: US 6,844,742 B2
• Time in Patent Office: Days
• US Class Current: 324/662
• CPC Class Codes: G01N 27/221 by investigating the dielectric properties using microwaves G01N22/00; measuring loss factors or dielectric constants per se G01R27/26

Abstract

A chemical concentration detecting system for determining the relative concentrations of a multiple component chemical solution. The multi-component solution is preferably comprised of an antimicrobial chemical and a base fluid that acts as a diluent for the antimicrobial chemical, or as a vehicle or carrier for the antimicrobial chemical. A capacitor is exposed to the decontamination solution, wherein the decontamination solution acts as the dielectric between the plates of the capacitor. Permittivity of the dielectric is affected by the relative concentrations of the components, and thus a measurement of the capacitance is used to determine the relative concentration levels of the components in the solution.

Claims

1. A chemical concentration detecting system for determining a concentration of a first component in a multi-component solution, comprising:

a capacitor having first and second plates exposed to the solution, said solution being a dielectric therebetween; and

processing means for determining a change in an electrical property of the capacitor, said change in the electrical property varying according to the concentration of the first component in the solution.

2. A chemical concentration detecting system according to claim 1, wherein said first capacitor is selected from the group consisting of:

a parallel plate capacitor, a cylindrical capacitor, and a spherical capacitor.

3. A chemical concentration detecting system according to claim 1, wherein said processing means includes a memory for storing a set of data including capacitance values and corresponding concentration values indicative of the relative concentration of the first component in the solution.

4. A chemical concentration detecting system according to claim 3, wherein said processing means obtains a relative concentration from said set of data, in accordance with said first capacitance.

5. A chemical concentration detecting system according to claim 3, wherein said processing means uses said set of data to interpolate or extrapolate a relative concentration corresponding to the first capacitance.

6. A chemical concentration detecting system according to claim 3, wherein said processing means normalizes said relative concentration to provide an absolute concentration of the first component of the solution.

7. A chemical concentration detecting system according to claim 1, wherein said multi-component solution is comprised of an antimicrobial chemical and a base fluid.

8. A chemical concentration detecting system according to claim 7, wherein said base fluid is at least one of:

(a) a diluent for the antimicrobial chemical, and (b) a vehicle for the antimicrobial chemical.

9. A chemical concentration detecting system according to claim 7, wherein said antimicrobial chemical is selected from a group consisting of:

a liquid and an oxidative gas.

10. A chemical concentration detecting system according to claim 9, wherein said antimicrobial chemical is selected from a group consisting of:

hydrogen peroxide, peracid, peracetic acid, bleach, ozone, ammonia, ethylene oxide, fluorine containing chemicals, and chlorine containing chemicals.

11. A chemical concentration detecting system according to claim 7, wherein said base fluid is selected from a group consisting of:

water, an alcohol, a glycol-containing chemical compound, and combinations thereof.

12. A chemical concentration detecting system according to claim 11, wherein said glycol-containing chemical compound is selected from a group consisting of:

polyethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, glycol ethers, polypropylene glycol, propylene glycol, and combinations thereof.

13. A chemical concentration detecting system according to claim 11, wherein said alcohol is a tertiary alcohol.

14. A chemical concentration detecting system according to claim 1, wherein said system further comprises:

a bridge circuit, wherein said capacitor forms a part of said bridge circuit.

15. A chemical concentration detecting system according to claim 14, wherein said bridge circuit includes a potentiometer having first and second resistances associated therewith, said processing means determining values of said first and second resistances when the bridge circuit is in a null condition to determine capacitance of said capacitor.

16. A method for determining a concentration of a first component in a multi-component chemical solution, comprising:

exposing a capacitor, having first and second parallel plates, to the solution, said solution comprising a dielectric therebetween; and

determining a change in an electrical property of the capacitor, said change in the electrical property varying according to the concentration of the first component in the solution.

17. A method according to claim 16, wherein said step of determining the change in an electrical property of the capacitor includes:

accessing pre-stored data including capacitance values and corresponding concentration values indicative of the concentration of the first component in the solution.

18. A method according to claim 17, wherein said step of determining the change in the electrical property of the capacitor includes:

interpolating or extrapolating from the pre-stored data the concentration of the first component in the solution.

19. A method according to claim 16, wherein said processing means normalizes said concentration to provide an absolute concentration of the first component of said solution.

20. A method according to claim 16, wherein said solution is comprised of an antimicrobial chemical and a base fluid.

21. A method according to claim 20, wherein said base fluid is at least one of:

(a) a diluent for the antimicrobial chemical, and (b) a vehicle for the antimicrobial chemical.

22. A method according to claim 20, wherein said antimicrobial chemical is selected from a group consisting of:

a liquid and an oxidative gas.

23. A method according to claim 20, wherein said antimicrobial chemical is selected from a group consisting of:

hydrogen peroxide, peracid, peracetic acid, bleach, ozone, ammonia, ethylene oxide, fluorine containing chemicals, and chlorine containing chemicals.

24. A method according to claim 20, wherein said base fluid is selected from a group consisting of:

water, an alcohol, a glycol-containing chemical compound, and combinations thereof.

25. A method according to claim 24, wherein said glycol-containing chemical compound is selected from a group consisting of:

polyethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, glycol ethers, polypropylene glycol, propylene glycol, and combinations thereof.

26. A method according to claim 24, wherein said alcohol is a tertiary alcohol.