Differential pH probe

Abstract

A differential pH probe design uses a container having an outer surface and an inner volume, where the inner volume is divided into a first chamber and a second chamber. A first pH-sensitive area is located on the outer surface of the first chamber where the first pH-sensitive area is configured to be exposed to a sample. A second pH-sensitive area is located on the outer surface of the second chamber where the second pH-sensitive area is shielded from the sample and is exposed to a buffer solution. A first electrode is configured to detect a first voltage in the first chamber and a second electrode is configured to detect a second voltage in the second chamber. Circuitry is coupled to the first and second electrodes and configured to process the first voltage and the second voltage to determine a pH of the sample.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates glass piece 100 used in differential pH probe 150, in an example embodiment of the invention.

FIG. 2 illustrates glass piece 100 with seals, in an example embodiment of the invention.

FIG. 3 illustrates glass piece 100 with seals and circuitry, in an example embodiment of the invention.

FIG. 4 illustrates differential pH probe 150, in an example embodiment of the invention.

FIG. 5 illustrates differential pH probe 150 with temperature sensors, in an example embodiment of the invention.

FIG. 6 illustrates glass piece 130 used in a differential pH probe in an example embodiment of the invention.

FIG. 7 illustrates a variation for conductive enclosure 120 in another example embodiment of the invention.

Claims

1. A differential pH probe, comprising: a container having an outer surface and an inner volume, where the inner volume is divided into a first chamber and a second chamber;a first pH-sensitive area on the outer surface of the first chamber where the first pH-sensitive area is configured to be exposed to a sample;a second pH-sensitive area on the outer surface of the second chamber where the second pH-sensitive area is shielded from the sample and is exposed to a buffer solution;a first electrode configured to detect a first voltage in the first chamber;a second electrode configured to detect a second voltage in the second chamber;circuitry coupled to the first and second electrodes and configured to process the first voltage and the second voltage to determine a pH of the sample.

2. The differential pH probe of claim 1 where the outer surface of the container is contiguous.

3. The differential pH probe of claim 1 where the container has a generalized cylindrical shape.

4. The differential pH probe of claim 3 where the first chamber is formed by one end of the generalized cylindrical shape and a first seal and the second chamber is formed by a middle section of the generalized cylindrical shape and a second and third seal.

5. The differential pH probe of claim 1 where the first pH-sensitive area forms a first shape and the second pH-sensitive area forms a second shape and where the first shape defines a first axis and the second shape defines a second axis and the first and second axis are co-axial.

6. The differential pH probe of claim 1 where the first pH-sensitive area is generally dome shaped and formed at a first end of the container.

7. The differential pH probe of claim 1 where the first pH-sensitive area forms a first cylindrical shape and the second pH-sensitive area forms a second cylindrical shape.

8. The differential pH probe of claim 7 where the first and second cylindrical shapes have the same diameter.

9. The differential pH probe of claim 1 further comprising: a third chamber where the third chamber is between the first and second chambers and the outer surface of the third chamber is not pH-sensitive.

10. The differential pH probe of claim 1 further comprising: a conductive enclosure where the conductive enclosure surrounds at least part of the outer surface of the container and where the conductive enclosure is coupled to a ground path in the circuitry.

11. The differential pH probe of claim 10 further comprising: a first seal and a second seal where the first and second seals couple to the outer surface of the container and an inner surface of the conductive enclosure to form a compartment that holds the buffer solution.

12. The differential pH probe of claim 10 where the compartment that holds the buffer solution is axially aligned with the first chamber.

13. The differential pH probe of claim 1 further comprising: a first temperature sensor coupled to the circuitry and configured to sense the temperature in the first chamber;a second temperature sensor coupled to the circuitry and configured to sense the temperature in the second chamber and where the circuitry is configured to compensate the determined pH for the temperature sensed in the first and second chambers.

14. The differential pH probe of claim 1 where the buffer solution has a pH of 7.

15. A differential pH probe, comprising: a generalized cylindrical container having an outer surface and an inner volume, where the inner volume is divided into a first chamber at a first end, a second chamber adjacent to the first chamber and a third chamber adjacent to the second chamber;a first part of the outer surface of the first chamber comprising a first pH-sensitive area where the first pH-sensitive area is configured to be exposed to a sample;the outer surface of the second chamber is not pH sensitive;a first part of the outer surface of the third chamber comprising a second pH-sensitive area where the second pH-sensitive area is immersed in a buffer solution;a first electrode configured to detect a first voltage in the first chamber;a second electrode configured to detect a second voltage in the third chamber;circuitry to process the first voltage and the second voltage to determine a pH of the sample.

16. The differential pH probe of claim 15 further comprising: a first seal forming a boundary between the first chamber and the second chamber;a second seal inserted into the generalized cylindrical container and forming a boundary between the second chamber and the third chamber;a third seal inserted into the generalized cylindrical container and forming an outer boundary of the third chamber.

17. The differential pH probe of claim 15 where a cross section of the generalized cylindrical shape is selected from one of the following: circle, square, rectangle, regular polygon, star polygon, ribbed circle, rounded rectangle, oval, spline, and ellipse.

18. The differential pH probe of claim 15 where the first end of the generalized cylindrical shape is generally dome shaped and forms the first pH-sensitive area.

19. The differential pH probe of claim 15 further comprising: a conductive enclosure where the conductive enclosure surrounds the second and third chambers and where the conductive enclosure is coupled to a ground path in the circuitry.

20. The differential pH probe of claim 19 further comprising: a first seal and a second seal where the first and second seals couple to the outer surface of the generalized cylindrical shape and an inner surface of the conductive enclosure to form a compartment that holds the buffer solution.

21. The differential pH probe of claim 15 further comprising: a first temperature sensor coupled to the circuitry and configured to sense the temperature of the sample;a second temperature sensor coupled to the circuitry and configured to sense the temperature in the third chamber and where the circuitry is configured to compensate the determined pH for the temperature sensed in the sample and the third chambers.

22. The differential pH probe of claim 15 where the buffer solution has a pH of 7.

23. The differential pH probe of claim 15 where the first chamber has a different shape than the third chamber.

24. The differential pH probe of claim 15 where the first chamber has a different diameter than the third chamber.

25. The differential pH probe of claim 15 where the first chamber and the third chamber are axially aligned.

26. A method of manufacturing a differential pH probe, comprising: forming a tube with two rings of pH sensitive material and two rings of non-pH sensitive material where the tube has alternating rings of pH sensitive material and non-pH sensitive material and where the tube has a closed end and where a first ring of pH sensitive material is at the closed end;dividing the tube into a first, a second and a third chamber where the first chamber corresponds to the first ring of pH sensitive material, the second chamber corresponds to a first ring of non pH sensitive material, and the third chamber corresponds to a second ring of pH sensitive material;inserting a first electrode into the first chamber and a second electrode into the third chamber and connecting the first and second electrodes to circuitry;immersing the second ring of pH sensitive material in a buffer solution.

27. The method of manufacturing a differential pH probe of claim 26, further comprising: surrounding the second and third chambers with a conductive enclosure and connecting a ground path in the circuitry to the conducting enclosure.

28. The method of manufacturing a differential pH probe of claim 26, further comprising: inserting a first temperature sensor into the first chamber and a second temperature sensor into the third chamber and connecting the first and second temperature sensor to the circuitry.