Ion concentration probe with enhanced shielding

Abstract

A probe (100) for measuring a sample solution includes an outer body (102) configured to receive an operational amount of a reference solution (120), and a sensor assembly (104) including an inner body (130), at least a portion of which is located within the outer body (102). A shield (156) is located between the outer surface (130) of the inner body and the inner surface (162) of the outer body (102). The shield (156) is configured to be in contact with and extend above the top surface (152) of the reference solution (120) when the probe (100) is filled with the operational amount of the reference solution (120).

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of co-pending U.S. Provisional Application Serial No. 62 / 936,850, filed November 18, 2020, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This invention relates generally to ion concentration measurement, and more particularly to ion concentration probes with enhanced shielding. Background Technology

[0004] Electrode-based ion measurement systems typically include a sensing electrode that responds to the specific ion being measured, and a reference electrode that provides a stable potential for comparison with the sensing electrode potential. In the case of pH measurement systems, the sensing electrode is typically a glass-based pH electrode. Glass-based pH electrodes generally have very high impedance and produce extremely weak voltage signals. These weak voltage signals make obtaining accurate measurement results difficult and pose challenges in designing electrodes and measurement systems to achieve optimal performance. The high impedance of the electrode tends to pick up electromagnetic interference, further complicating the weak voltage signal.

[0005] To reduce electromagnetic interference caused by factors such as static charge from hands, lab coats, etc., and localized electrical noise, electrodes are typically shielded from external signals. Traditional shielding involves wrapping a conductive material (e.g., copper foil) around the electrode body and directly connecting the conductive material to a reference electrode, which in turn is connected to the instrument ground. However, this shielding method is not suitable for probes with combined sensing-reference electrodes. Combined sensing-reference electrodes consist of a conductive reference solution, in which the reference electrode is immersed and the conductive reference solution surrounds the sensing electrode body. Conventional methods of shielding these types of probes rely on shielding provided by the reference solution beneath the filler wire and the conductive material wrapped around the outer body and connected to the instrument ground above the filler wire.

[0006] The aforementioned shielding methods complicate electrode design and increase the difficulty of probe manufacturing. Furthermore, the design requirement for internal electrode contact often limits the effectiveness of traditional shielding. Therefore, improved equipment and methods are needed to shield the sensing electrodes used in ion measurement systems. Summary of the Invention

[0007] In an embodiment of the invention, a probe for measuring a first solution is provided. The probe includes an outer body, a sensor assembly, and a shield. The outer body has an inner surface and is configured to receive an operational amount of a second solution having a top surface. The sensor assembly includes an inner body having an outer surface, and at least a portion of the inner body is located within the outer body. The shield is located between the outer surface of the inner body and the inner surface of the outer body, and is configured to contact the second solution and extend above the top surface of the second solution when the probe is filled with an operational amount of the second solution during use of the probe.

[0008] In this invention, the probe may further include a reference electrode, at least a portion of which may be located within the outer body and outside the inner body, and in contact with the second solution when the probe is filled with an operating amount of the second solution.

[0009] In another aspect of the invention, the reference electrode may be located in the outer body, such that a first gap exists between the shield and the reference electrode.

[0010] In another aspect of the invention, the shield may have an inner surface, and the first gap may be located between the reference electrode and the inner surface of the shield.

[0011] In another aspect of the invention, the shield may have an outer surface, and the first gap may be between the reference electrode and the outer surface of the shield.

[0012] In another aspect of the invention, when the probe is filled with an operating amount of the second solution, the shield can be electrically coupled to the reference electrode through the second solution.

[0013] In another aspect of the invention, the probe may further include a connector having a ground conductor, and the shield may be electrically coupled to the ground conductor of the connector.

[0014] In another aspect of the invention, the shielding member may extend above the top surface of the second solution to the connector.

[0015] In another aspect of the invention, the shielding element may be electrically coupled to the grounding conductor of the connector at the connector.

[0016] In another aspect of the invention, the reference electrode may be electrically coupled to the ground conductor of the connector.

[0017] In another aspect of the invention, the shielding element can be electrically coupled to the grounding conductor of the connector via a second solution and a reference electrode.

[0018] In another aspect of the invention, the probe may further include a liquid junction configured to electrically couple charges between the first and second solutions when the probe is filled with an operating amount of the second solution and immersed in the first solution during use of the probe.

[0019] In another aspect of the invention, the shielding member can be electrically coupled to the instrument ground via the second solution and liquid junction.

[0020] In another aspect of the invention, the inner body may include a lower end, the lower end including a chamber having an upper portion and a lower portion, and the lower portion of the chamber may be defined by a membrane connected to the upper portion of the chamber, such that a joint is formed between the membrane and the upper portion of the chamber.

[0021] In another aspect of the invention, the outer body may include a lower end having an opening, the inner body and the outer body may be configured such that a liquid-tight seal is provided between the inner body and the outer body at the opening, and the connector between the membrane and the upper part of the chamber may be located below the liquid-tight seal such that the membrane does not contact the second solution when the probe is filled with an operating amount of the second solution.

[0022] In another aspect of the invention, the membrane may include a first material that allows ion exchange, and the upper part of the chamber may include a second material that is electrically insulating.

[0023] In another aspect of the invention, the sensor assembly may further include a third solution within the internal body and a sensing electrode, at least a portion of which is located within the internal body and in contact with the third solution.

[0024] In another aspect of the invention, the shielding member may contact the outer surface of the inner body.

[0025] In another aspect of the invention, the shielding member may have an inner surface and an outer surface, and a second gap may exist between the inner surface of the shielding member and the outer surface of the inner body, and a third gap may exist between the outer surface of the shielding member and the inner surface of the outer body.

[0026] The foregoing summary presents a simplified overview of some embodiments of the invention to provide a basic understanding of certain aspects of the invention discussed herein. This summary is not intended to provide a broad overview of the invention, nor is it intended to identify any key or principal elements, or to depict the scope of the invention. The sole purpose of this summary is to present some concepts in a simplified form as an introduction to the detailed description that follows. Attached Figure Description

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the general description of the invention given above and the detailed description of the invention given below, serve to explain the principles of the invention.

[0028] Figure 1 This is a perspective view of an exemplary probe according to an embodiment of the present invention.

[0029] Figure 2 yes Figure 1 A schematic front view of the probe.

[0030] Figure 3 yes Figure 2 A vertical sectional view of the probe.

[0031] Figure 4 yes Figure 3 An enlarged view of a portion of the probe, showing other details of the probe.

[0032] Figure 5 yes Figure 2 A horizontal cross-sectional view of the probe.

[0033] Figure 6 This is a vertical sectional view of an exemplary probe according to another embodiment of the present invention.

[0034] Figure 7 yes Figure 6 A horizontal cross-sectional view of the probe.

[0035] Figure 8 This is a vertical sectional view of an exemplary probe according to another embodiment of the present invention.

[0036] Figure 9 yes Figure 8 A horizontal cross-sectional view of the probe.

[0037] Figure 10 This is a vertical sectional view of an exemplary probe according to another embodiment of the present invention.

[0038] Figure 11 yes Figure 10 A horizontal cross-sectional view of the probe. Detailed Implementation

[0039] Embodiments of the present invention enhance the coverage and effectiveness of the internal electrical shielding of pH and ion-selective electrodes. Improvements in shielding also improve manufacturability by reducing the need for wiring in the probe and enhance the shielding provided by the reference solution below the fill line defined by the top surface of the reference solution.

[0040] Figure 1 and Figure 2 A probe 100 according to an embodiment of the present invention is depicted. The probe 100 includes a hollow cylindrical outer body 102 and a sensor assembly 104. The outer body 102 includes an upper end 106 and a lower end 108, each of the upper and lower ends including a corresponding opening 110, 112. Figure 3The probe 100 also includes a membrane 114 (e.g., a glass membrane) extending outward from the opening 112 at the lower end 108 of the outer body 102. The membrane 114 may be part of the sensor assembly 104 and may be flat, curved (e.g., circular), or have any other suitable shape. The membrane 114 is made of a material sensitive to one or more specific types of ions (e.g., hydrogen ions). Suitable materials for the membrane 114 may include doped glass, crystals, polymers, or other types of materials that allow ion exchange. The outer body 102 is made of an electrically insulating material (e.g., silicate-based glass or chemically resistant plastic) and includes a liquid junction 116 and a filling orifice 118. The filling orifice 118 provides an opening through which a reference solution 120 (…) can be introduced. Figure 3 Add to probe 100.

[0041] The liquid junction 116 of the outer body 102 may include pores filled or otherwise blocked with a porous material (e.g., ceramic or capillary material) that allows the sample solution immersed in the probe 100 to exchange charges (e.g., ions, protons, or electrons) with the reference solution 120. The liquid junction 116 may be located on the outer body 102 such that it is in contact with both the reference solution 120 and the sample solution (not shown) while the probe 100 measures the sample solution. The liquid junction 116 may have any suitable shape, such as circular, and provide a path for current to flow between the reference solution and the sample solution.

[0042] The probe 100 also includes a reference electrode 122 and a sensing electrode 124. A portion of each electrode 122, 124 may extend outward from the upper end 106 of the outer body 102 to form corresponding terminals 126, 128. Terminals 126, 128 may be configured to connect the probe 100 to a measuring device, such as a pH meter (not shown).

[0043] Now for reference Figures 3-5 And continue to refer to Figure 1 and Figure 2 , Figure 3 It is along Figure 2 The sectional view taken from line 3. Figure 4 yes Figure 3 The enlarged portion of the sectional view, and Figure 5 The embodiment of probe 100 along Figure 2A cross-sectional view taken from line 4. The sensor assembly 104 includes a sensing electrode 124 and an internal body 130 configured to receive a quantity of sensing solution 132 that at least partially fills the internal body 130. The internal body 130 includes a hollow rod 134 in fluid communication with a chamber 136 having an upper portion 138 and a lower portion 140. The lower portion 140 of the chamber 136 may be defined by a membrane 114, and the upper portion 138 of the chamber 136 may be defined by a portion of the internal body 130 that connects the membrane 114 to the rod 134. In embodiments of the invention, the upper portion 138 of the chamber 136 may be provided by an open or otherwise extended portion of the rod 134.

[0044] The chamber 136 can be formed by fusing or otherwise attaching the membrane 114 to the upper portion 138 of the chamber 136. This fusing can form a joint 142 between the membrane 114 and the upper portion 138 of the chamber 136. The chamber 136 can form a liquid-tight seal 144 with the opening 112 at the lower end 108 of the outer body 102. Figure 4 The seal 144 may be located near or above the joint 142 of the chamber 136, such that the outer surface of the membrane 114 does not contact the reference solution 120. The seal 144 may be provided by a gasket or other sealing member or material, by fusing the outer surface of the chamber 136 to the outer body 102 along the periphery of the opening 112, or by any other suitable method.

[0045] The sensing electrode 124 can extend into the inner body 130 through an opening at the upper end of the rod 134. The rod 134 includes an outer surface 146 and an inner surface 148. The inner diameter of the rod 134 may be slightly larger than the diameter of the sensing electrode 124, such that a gap 150 exists between the outer surface of the sensing electrode 124 and the inner surface 148 of the rod 134. The gap 150 may be filled with a sensing solution 132 along at least a portion of the length of the rod 134.

[0046] The membrane 114 may protrude through or otherwise span at least a portion of the opening 112 of the outer body 102 such that the membrane 114 is exposed to the sample solution when the probe 100 is immersed in the solution. The sensing solution 132 may include a buffered potassium chloride solution or other electrolyte solutions having a concentration, for example, between 0.01 and 5.0 mol, and may be in contact with at least a portion of the sensing electrode 124.

[0047] Ideal properties of the material used to form membrane 114 may include relatively low electrical resistance and high chemical resistance. Details regarding suitable materials for manufacturing membrane 114 can be found in U.S. Patent Nos. 4,297,193 and 4,028,196, the disclosures of which are incorporated herein by reference in their entirety. Conversely, the rod 134 and upper portion 138 of chamber 136 may be made of glass or other suitable materials that are unresponsive to the ions being measured. Ideal properties of such materials may include low electrical conductivity and high chemical resistance.

[0048] The space between the outer body 102 and the inner body 130 may contain a reference solution 120. The reference solution 120 has a top surface 152 and may comprise a potassium chloride solution or other electrolyte solutions having a concentration, for example, between 0.01 and 5.0 mol. The reference solution 120 may be added to the probe 100 through the filling orifice 118 in an amount sufficient to allow contact between the reference solution 120 and the lower portion 154 of the reference electrode 122.

[0049] The probe 100 also includes an electromagnetic shield 156 having an inner surface 158 and an outer surface 160. The shield 156 may be located between the outer body 102 and the inner body 130, extending at least a portion of the length of the outer body 102. The shield 156 may comprise a layer of conductive material deposited on the inner surface 162 of the outer body 102, or otherwise contact the inner surface of the outer body, for example, by inserting a section of tubing into the outer body 102. This tubing may have an outer diameter that is the same as or slightly smaller than the inner diameter of the outer body 102. The shield 156 may be held in place by friction against the inner surface 162 of the outer body 102 or by any other suitable method (e.g., adhesive, clamp, etc.).

[0050] The shield 156 may extend along the length of the outer body 102 from below the top surface 152 of the reference solution 120, or just near the upper end 106 of the outer body 102. The shield 156 may extend the shielding of the sensor assembly 104 provided by the reference solution 120 above the top surface 152 of the reference solution 120. The reference solution 120 may be grounded via the reference electrode 122 (or otherwise coupled to a reference voltage, such as instrument ground), thereby providing shielding for the portion of the sensor assembly 104 below the top surface 152 of the reference solution 120.

[0051] The maximum amount of reference solution 120 that can be added to probe 100 can be an amount sufficient to hold the top surface 152 of reference solution 120 at or immediately below the filling orifice 118. The minimum amount of reference solution 120 that can be added to probe 100 can be an amount sufficient to hold the top surface 152 of reference solution 120 above the lower end 154 of reference electrode 122 and the lower end of shield 156. Therefore, the operating amount of reference solution can be an operating fill level that produces an operating fill level between the minimum and maximum fill levels and causes at least a portion of reference electrode 122 and shield 156 to be in contact with reference solution 120 during use of probe 100.

[0052] In embodiments of the invention, the shield 156 may be electrically coupled to the grounding conductor of the cable connecting the probe 100 to the instrument. This grounding coupling may be via the reference electrode 122 through the reference solution 120, via a direct connection to the grounding conductor of the cable connecting the probe 100 to the instrument, or via the reference solution 120 and a direct connection to the grounding conductor. In embodiments where the shield 156 is directly connected to the grounding conductor, the shield 156 may also serve as a reference electrode, in which case the reference electrode 122 may be omitted.

[0053] For example, the cable may include a central conductor operatively coupled to the sensing electrode 124, a tubular inner insulation layer surrounding the central conductor, a tubular outer conductive layer operatively coupled to the reference electrode 122 surrounding the insulation layer, and an outer insulation layer or sheath. The outer conductive layer of the cable may thereby extend the shielding provided by the reference solution 120 and the shielding member 156 to the instrument connection.

[0054] Figure 6 and Figure 7 Alternative embodiments of probe 100 are respectively along Figure 2 The cross-sectional view taken by lines 3 and 4. This embodiment replaces... Figures 3-5 The shielding element 156 depicted has an electromagnetic shielding element 164 having an inner surface 166 and an outer surface 168. The shielding element 164 comprises a layer of conductive material deposited on or otherwise in contact with the outer surface 146 of the rod 134. For example, the shielding element 164 may be provided by the length of a tube inserted into the inner body 130, the inner diameter of which is the same as or slightly larger than the outer diameter of the rod 134. The shielding element 164 may extend along the length of the inner body 130 from below the top surface 152 of the reference solution 120, or just near the upper end 106 of the outer body 102. (As described above regarding...) Figures 3-5As described, shielding 164 can extend the shielding of sensor assembly 104 provided by reference solution 120 over the top surface 152 of reference solution 120. In embodiments of the invention, as described above with respect to shielding 156, shielding 164 can be electrically coupled to the grounding conductor of the cable connecting probe 100 to the instrument.

[0055] Figure 8 and Figure 9 Another alternative embodiment of probe 100 is along Figure 2 The cross-sectional view taken by lines 3 and 4. This embodiment replaces... Figure 6 and Figure 7 The shielding element 164 depicted has an electromagnetic shielding element 170 having an inner surface 172, an outer surface 174, and a helical shape. The shielding element 170 comprises a layer of conductive material deposited on or otherwise in contact with the outer surface 146 of the circular helical rod 134. For example, the shielding element 170 can be manufactured by winding a section of conductive material around a rod with a diameter approximately the same as the outer diameter of the rod 134 of the inner body 130, and then sliding the resulting helix along the rod 134. The shielding element 170 can also be deposited on the rod 134 and selectively etched to define the helix, or a mask deposition can be used to prevent conductive material from covering areas of the rod 134 between adjacent portions of the helix.

[0056] In any case, the shield 170 may extend along the length of the inner body 130 from below the top surface 152 of the reference solution 120 to the upper end 106 of the outer body 102, or just near the upper end of the outer body. (As mentioned above regarding...) Figures 3-7 As described, shielding 170 can extend the shielding of sensor assembly 104 provided by reference solution 120 over the top surface 152 of reference solution 120. In embodiments of the invention, as described above with respect to other embodiments of shielding 156, 164, shielding 170 can be electrically coupled to the grounding conductor of the cable connecting probe 100 to the instrument.

[0057] Figure 10 and Figure 11 This is another alternative embodiment of probe 100 along Figure 2 The cross-sectional view taken by lines 3 and 4. This embodiment replaces... Figures 3-5The shielding member 156 depicted includes an electromagnetic shielding member 176 having an inner surface 178 and an outer surface 180. The shielding member 176 comprises a conductive material tube spaced apart from the outer surface 146 of the rod 134 by a gap 182 and from the reference electrode 122 by a gap 184. In an alternative embodiment, the diameter of the shielding member 176 may be large enough that both the rod 134 and the reference electrode 122 are surrounded by the shielding member 176, in which case the reference electrode 122 would be located between the inner surface 178 of the shielding member 176 and the outer surface 146 of the rod 134.

[0058] The shield 176 may include a conductive tube inserted into the inner body 130, with an inner diameter slightly larger than the outer diameter of the rod 134 of the inner body 130 (when the shield 176 is located between the reference electrode 122 and the rod 134) or significantly larger (when the shield surrounds the reference electrode 122 and the rod 134). The shield 176 may be laterally positioned relative to the outer body 102, the reference electrode 122, or the rod 134 by one or more spacers (not shown). The shield 176 may extend along the length of the inner body 130 from below the top surface 152 of the reference solution 120, or just near the upper end 106 of the outer body 102. As mentioned above regarding Figures 3-9 The shielding element 176 can extend the shielding of the sensor assembly 104 provided by the reference solution 120 above the top surface 152 of the reference solution 120. In embodiments of the invention, as described above with respect to other embodiments of shielding elements 156, 164, 170, shielding element 176 can be electrically coupled to the grounding conductor of the cable connecting the probe 100 to the instrument.

[0059] The shielding described herein can be formed from a continuous overlay of conductive or semiconductive material, or from a discontinuous overlay. Exemplary discontinuous overlays may include, but are not limited to, grids, screens, perforated sheets, or other patterns of one or more electrically coupled conductive elements. Although the shielding is generally described above as having a cylindrical shape, embodiments of the invention are not limited thereto. For example, the shielding may have an elliptical, polygonal, or other cross-section, and may have a cross-section that varies in size or shape along the length of the shielding.

[0060] The conductive material used to fabricate the shield may include one or more metals generally known to be suitable for electrodes, such as, but not limited to, silver, gold, platinum, copper, titanium, and their alloys. For embodiments where the shield is deposited as a layer on a substrate (e.g., on the inner surface 162 of the outer body 102 or the outer surface 146 of the rod 134), the shield may also include an adhesion enhancement layer deposited on the substrate prior to the deposited conductive material. Exemplary materials that can be used for the adhesion enhancement layer include one or more of titanium, chromium, molybdenum, tantalum, tungsten, gold, and palladium.

[0061] The conductivity required for effective shielding by the conductive coating on the outer body 102 or the inner body 130 may be relatively low. That is, the conductive coating can be highly conductive (e.g., metallic) or only semi-conductive (e.g., semiconductor). Coating materials with resistances up to 127 Ω-m have been shown to provide effective shielding. Therefore, the shield can also be formed from non-metallic materials, such as ceramics. For example, the shield can be made of indium tin oxide, which, in addition to having sufficient conductivity, also possesses optical transparency and durability. Due to its excellent chemical compatibility and adhesion to glass, titanium can also be used as a conductive material for continuous contact between the coating and the reference solution 120.

[0062] In embodiments where a shielding element is applied as a coating, the coating can be applied to a substrate by applying a liquid composition, which is converted into a solid film by solvent evaporation or by chemical reaction or any other suitable method of depositing conductive materials, using any suitable method or combination of methods (e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD), electrochemical plating, electroless plating, sputtering).

[0063] Advantageously, embodiments of the invention in which the shielding is defined by depositing a conductive coating on the inner surface 162 of the outer body 102 or the outer surface 146 of the inner body 130 can provide more effective shielding for the sensor assembly 104 than conventional shielding methods. The deposited conductive shielding can also improve manufacturability, maintain the clean appearance of the glass electrodes, and allow the probe 100 to have few or no interconnects in a compact portion of the probe 100 where effective shielding is difficult.

[0064] According to an embodiment of the invention, a shield can extend along the length of the probe 100 from below the top surface 152 of the reference solution 120 or just near the upper end 106 of the outer body 102. The shield can extend from below the top surface 152 of the reference solution 120 such that it contacts the conductive reference solution 120. Therefore, the shield can be electrically coupled to the reference potential of the probe 100. This embodiment of the invention thus preserves the existing level of shielding provided to the signal received by the reference solution 120 from the membrane 114, while adding additional shielding above and below the top surface 152 of the reference solution 120. The shield can thus extend the shielding of the sensor assembly 104 provided by the reference solution 120 above the top surface 152 of the reference solution 120, which is typically confined to the level below the filling orifice 118. The shield can also be electrically coupled to the grounding conductor of the cable connecting the probe 100 to the instrument, for example, through a connector (not shown) configured to operatively couple to the outer conductor (not shown) of a coaxial cable.

[0065] Another advantage of embodiments of the invention is that when the conductive coating is deposited on the inner or outer body, it effectively extends the shielding to points below and above the filling orifice 118. Therefore, even at low reference solution levels, the shielding provides complete coverage and extends the shielding above the maximum solution fill level, which is limited by the location of the filling orifice 118. Because the coating is in contact with the reference solution, no physical wiring is required to complete the shielding connection, and the sensor assembly 104 can be installed more simply compared to probes lacking this feature.

[0066] In another embodiment of the invention, the outer surface of the outer body 102 may be coated with a transparent conductive material, such as indium tin oxide. The conductive material coating can be applied from the upper end 106 of the outer body 102 to the area terminating below the filling hole 118 but above the probe immersion point. The conductive material coating can be electrically coupled to the shielding at a point within the nut using conductive epoxy, spring connections, or any other suitable method that enables simple and reliable assembly. Using a transparent conductive material coating on the glass outer body maintains the probe's aesthetics while significantly improving resistance to external noise.

[0067] The conductive material in contact with the reference solution should be chemically compatible with the solution. Compatible materials may include titanium, metal-coated plastic films, and indium tin oxide-coated plastic films. These films can be flexible enough to wrap around an inner or outer body, or form a tube. For example, the conductive film can be mounted by wrapping the film around an inner body 130 or forming a tube around the inner body, which is in contact with the reference solution. Similar to the coated inner body style, the connection between the shield and the reference can be made through the reference solution, eliminating the need for a wired shield connection. In another embodiment, the conductive film can be mounted by forming a tube that conforms to the inner surface 162 of the outer body 102.

[0068] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. As used herein, unless the context clearly indicates otherwise, the singular forms “a” (“a”, “an”) and “the” (“the”) are intended to include both singular and plural forms, and the terms “and” and “or” are each intended to include alternative and connecting combinations. It will be further understood that, when used in this specification, the term “comprises” or “comprising” specifies the presence of the said feature, integer, action, step, operation, element, or component, but does not exclude the presence or addition of one or more other features, integers, actions, steps, operations, elements, components, or groups thereof. Furthermore, with regard to the extent to which the terms “includes,” “having,” “has,” “comprised of,” or variations thereof are used in the detailed description and claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” Additionally, the dimensions of certain portions of the drawings may not be drawn to scale or may be exaggerated for clarity.

[0069] While the invention has been described by way of exemplary embodiments and while these embodiments have been described in considerable detail, the applicant does not intend to limit the scope of the appended claims or in any way restrict it to such details. Additional advantages and modifications will readily be apparent to those skilled in the art. Therefore, the invention is not, in its broader aspects, limited to the specific details, representative devices and methods, and illustrative examples shown and described. Consequently, deviations from these details may be made without departing from the spirit or scope of the applicant's general inventive concept.

Claims

1. A probe for measuring a first solution, the probe comprising: an outer body including an inner surface and configured to receive an operational amount of a second solution, the second solution including a top surface; a sensor assembly including an inner body having an outer surface, at least a portion of the inner body being located within the outer body; and a shield located between the outer surface of the inner body and the inner surface of the outer body, the shield surrounding the outer surface and configured to be in contact with the second solution and to extend above the top surface of the second solution when the probe is filled with the operational amount of the second solution during use of the probe.

2. The probe of claim 1, wherein the shield is electrically coupled to: a ground conductor of a connector, the ground conductor being through the second solution and a reference electrode, or an instrument ground, the instrument ground being through the second solution and a liquid junction.

3. The probe of claim 1 or 2, further comprising: a reference electrode, at least a portion of the reference electrode being located within the outer body, outside the inner body, and in contact with the second solution when the probe is filled with the operational amount of the second solution.

4. The probe of claim 3, wherein the reference electrode is located in the outer body such that a first gap exists between the shield and the reference electrode.

5. The probe of claim 4, wherein the shield has an inner surface, and the first gap is between the reference electrode and the inner surface of the shield.

6. The probe of claim 4, wherein the shield has an outer surface, and the first gap is between the reference electrode and the outer surface of the shield.

7. The probe of claim 3, wherein the shield is electrically coupled to the reference electrode through the second solution when the probe is filled with the operational amount of the second solution.

8. The probe of claim 1 or 2, further comprising: a connector including a ground conductor, wherein the shield is electrically coupled to the ground conductor of the connector.

9. The probe of claim 8, wherein the shield extends above the top surface of the second solution to the connector.

10. The probe of claim 8, wherein the shield is electrically coupled to the ground conductor of the connector at the connector.

11. The probe of claim 8, including a reference electrode, wherein the reference electrode is electrically coupled to the ground conductor of the connector.

12. The probe of claim 11, wherein the shield is electrically coupled to the ground conductor of the connector through the second solution and the reference electrode.

13. The probe of claim 1 or 2, further comprising: a liquid junction configured to electrically couple charge between the first solution and the second solution when the probe is filled with the operational amount of the second solution and immersed in the first solution during use of the probe.

14. The probe of claim 13, wherein the shield is electrically coupled to an instrument ground through the second solution and the liquid junction.

15. The probe of claim 1 or 2, wherein the inner body includes a lower end comprising a chamber having an upper portion and a lower portion, the lower portion of the chamber defined by a membrane connected to the upper portion of the chamber such that a joint is formed between the membrane and the upper portion of the chamber.

16. The probe of claim 15, wherein: the outer body includes a lower end having an opening, the inner body and the outer body are configured such that there is a liquid-tight seal between the inner body and the outer body at the opening, and the joint between the membrane and the upper portion of the chamber is located below the liquid-tight seal such that the membrane does not contact the second solution when the probe is filled with the operational amount of the second solution.

17. The probe of claim 15, wherein the membrane comprises a first material that allows ion exchange and the upper portion of the chamber comprises a second material that is electrically insulating.

18. The probe of claim 1 or 2, wherein the sensor assembly further comprises: a third solution within the inner body; and a sensing electrode having at least a portion located within the inner body and in contact with the third solution.

19. The probe of claim 1 or 2, wherein the shield is in contact with the outer surface of the inner body.

20. The probe of claim 1 or 2, wherein the shield has an inner surface and an outer surface, and there is a second gap between the inner surface of the shield and the outer surface of the inner body, and a third gap between the outer surface of the shield and the inner surface of the outer body.

21. The probe of claim 1 or 2, wherein there is no physical wiring used to complete the shield connection.

22. The probe of claim 1 or 2, wherein the shield is defined by depositing a conductive coating on an inner surface of the outer body or an outer surface of the inner body, wherein the coating material has an electrical resistance up to 127 Ω-m.

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