Liquid sensor for use with fluids with high resistance and low electrical conductivity

Abstract

A liquid sensor for use with a fluid with low electrical conductivity, includes a plurality of electrodes configured to have a first end and a second end, a spacer defining a predetermined gap between each of the plurality of electrodes, the spacer insulates between each of the plurality of electrodes, a plurality of sensor wires, one of the plurality of sensor wires attached to one of the plurality of electrodes, each of the plurality of electrodes includes at least one measurement face, where the at least one measurement face of any one of the plurality of electrodes is configured in a measurement pair with another of the at least one measurement face of any other one of the plurality of electrodes, the measurement pair configured to be separated by the predetermined gap, and a resistance value can be measured between the measurement pair.

Description

LIQUID SENSOR FOR USE WITH FLUIDS WITH HIGH RESISTANCE AND LOW ELECTRICAL CONDUCTIVITY.CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from US Provisional Patent Application No. 63 / 592,601 filed on October 24, 2023.BACKGROUND

[0002] Presently, there is a limited ability to readily detect the presence of fluids in their liquid state, in applications where the fluid has low electrical conductivity, and is used as a process fluid where a phase change occurs. Direct differentiation of the fluid’s phase state, as liquid or as a gas, is challenging when the fluid’s electrical resistivity does not appreciably change between fluid phase states, such as with deionized or ultrapure water, in steam generation applications. In such applications, the water’s low electrical conductivity, in any of its phase states, is a result of its purity. The electrical conductivity of deionized water can be as low as 0.2 micro Siemens per centimeter (pS / cm) and distilled or otherwise pure water can have electrical conductivities between 0.5-3.0 pS / cm. In such systems, the phase state is difficult to determine using traditional means, which rely on large differences in electrical capacitance or electrical resistance or may not be feasible to implement in all environments, such as detecting the phase state with radio waves. In common applications that utilize ultrapure water to generate steam, there are precise expectations and requirements regarding when, and where, within the system, the different phase states of liquid and vapor should exist.

[0003] Superheated steam systems used for common applications are designed such that the phase state of the process fluid, water, is known throughout the system with a very high certainty. In the example of steam turbines, the presence of water is not expected except when, and where, it is intended to exist, based upon its well-understood and accepted physical properties. An application utilizing superheated steam for power generation will often be designed with an absence of liquid-phase water in the early- to mid- stages of the steam turbine, due to the calculated temperatures and pressures of the steam exceeding those combinations of temperature and pressure where liquid water may exist. In steam turbine components, blade failures, blade damage, or blade erosion can be observed on turbine blades that make unexpected or unintentional contact with water in its liquid phase, while rotating atnormal operational velocities. Such consequences create a need to detect liquid water in these harsh or challenging environments. In the example of steam turbines, the presence of water is not expected and previously not thought to be possible in early to mid-stages of the steam turbine due to the calculated temperatures and pressures of the steam within the steam turbine at the mid-stages. In these environments, conventional liquid detectors utilize or measure a resistance or capacitance value, these sensors cannot reliably detect liquids with low electrical conductivities.

[0004] Conventional liquid detectors measure resistance or capacitance of the process fluid, and these sensors are not reliable, or repeatable with liquids with low electrical conductivities. Furthermore, such conventional sensors are rarely rated for the relatively extreme environmental conditions found in superheated steam systems. One such solution for the detection of liquid phase water, in environments where only vapor phase water should exist, is the use of appropriately rated thermocouples. Such sensors rely on the implication that liquid water exists when there is measurement and observation of a local, and sufficiently large, decrease in temperature within a portion of the steam system. In the example of a superheated steam system, any liquid water must have a lower temperature than the surrounding superheated steam, even if the liquid is transient, and only present briefly. A thermocouple could theoretically detect the presence of water if located in an area where the water might pool, coalesce, or otherwise contact the thermocouple. This method of detection has the disadvantage of requiring a quantity of liquid with enough thermal mass to contact or submerge the thermocouple to change the temperature of the thermocouple a sufficiently large amount, which may not be feasible, depending on the location of the desired measurement. A further disadvantage of the use of thermocouples, is resolution and response time. Even if the thermocouples are positioned in the optimal location for contact with water, there is a delay from when the thermocouple is first in contact with water, and when the lower temperature can be accurately measured by the thermocouple. The volume of water and frequency of contact between the thermocouple and the liquid water will affect the observed temperature, and the confidence of the conclusions made from the data. Either disadvantage could allow for the presence of liquid phase water to go undetected, resulting in a condition where blade erosion or blade failure occurs from contact with liquid water at operational blade velocities.

[0005] The present invention can advantageously be used to detect the difference in some fluid phase states directly, whereby it reliably measures the relatively large resistances of fluids withlow electrical conductivity, which in turn can be used to confirm the presence of the liquid phase state in fluids with low electrical conductivity.BRIEF SUMMARY

[0006] It is therefore a goal of the present invention to provide a liquid sensor that overcomes the above-mentioned disadvantage(s). In particular, a liquid sensor for use with a fluid with low electrical conductivity.

[0007] The object of the invention is achieved by, a liquid sensor for use with a fluid with low electrical conductivity, includes a plurality of electrodes configured to have a first end and a second end, a spacer defining a predetermined gap between each of the plurality of electrodes, the spacer insulates between each of the plurality of electrodes, a plurality of sensor wires, one of the plurality of sensor wires attached to one of the plurality of electrodes, each of the plurality of electrodes includes at least one measurement face, where the at least one measurement face of any one of the plurality of electrodes is configured in a measurement pair with another of the at least one measurement face of any other one of the plurality of electrodes, the measurement pair configured to be separated by the predetermined gap, and a resistance value can be measured between the measurement pair. In one embodiment the spacer can be a single piece, such as an extrusion or multiple spacers between each electrode. In one embodiment the electrodes can be attached to the spacer or spacers forming an electrode assembly.

[0008] In one embodiment, the liquid sensor may also include where the liquid sensor can detect resistance in fluids with conductivities of at least 0.2pS / cm.

[0009] In one embodiment, the liquid sensor may also include where the liquid sensor can detect a resistance value of deionized water.

[0010] In one embodiment, the liquid sensor may also include where the liquid sensor can operate in corrosive and or high temperature environments. In one embodiment the electrodes of the liquid sensor are advantageously manufactured from corrosive resistant materials such as stainless steel.

[0011] In one embodiment, the liquid sensor may also include where the at least one measurement face further includes a surface area.

[0012] In one embodiment, the liquid sensor may also include where the surface area is 0.016 in2. In one embodiment the surface area of the measurement face is advantageously sized to increase the accuracy or sensitivity of the liquid sensor. Advantageously, in one embodiment the measurement face of one electrode is spaced apart from the measurement face of another electrode, creating a measurement set with a measurement set surface area equal to the sum of two measurement faces, e.g., 0.032 in2. In one embodiment an electrode assembly has 4 measurement sets and a total surface area equal to the sum of each measurement set’s surface area, e.g. 0.128 in2.

[0013] In one embodiment, the liquid sensor may also produce a measurement that is at or below 1 Mohm. The liquid sensor can advantageously produce a resistance value between a range of 0 to over 1 mega ohm.

[0014] In one embodiment, the liquid sensor may also include, where the predetermined gap is between a range of 0.008" and 0.010". In one embodiment the predetermined gap is advantageously designed to produce capillary action in the intended fluid with low thermal conductivity. The predetermined gap can be increased or decreased to maximize the capillary action based on the physical properties of the liquid with low thermal conductivity and the intended environment.

[0015] In one embodiment, the liquid sensor may also include where the predetermined gap is 0.010". The predetermined gap can be increased or decreased to maximize the sensitivity of the liquid sensor, e.g., increasing or decreasing the expected resistance value(s). In one embodiment, the liquid sensor may advantageously detect an exact resistance value of a liquid with low electrical conductivity. In one embodiment, the liquid sensor may advantageous be designed to measure a first resistance value in the presence of the liquid phase of the liquid with low electrical conductivity and a second resistance value in the absence or vapor state of the liquid with low electrical conductivity; the difference between the first and second resistance values can advantageously be large. In one embodiment the difference between the first and second resistance values can be between a factor of 10 to 100. In one embodiment the difference between the first and second resistance values can advantageously be a factor greater than 100. In one embodiment the resistance value of deionized water measured by the liquid sensor is in the K ohm range.

[0016] In one embodiment, the liquid sensor may also include a sensor body where at least a portion of the liquid sensor is enclosed within the sensor body. In one embodiment theelectrodes have an electrode length that is covered by the spacer for the length of the spacer and uncovered at a sensor end of the electrode assembly. The sensor body advantageously encloses the electrode assembly including the spacer length. The sensor end is advantageously uncovered for direct contact with the intended liquid.

[0017] In one embodiment, the liquid sensor may also include a potting material where the potting material fills in a gap between the sensor body and the electrode assembly of the liquid sensor. In one embodiment the potting material fills the gap between the internal cavity of the sensor body and the exterior of the electrode assembly.

[0018] In one embodiment, a method of soldering an electrical connection of an electrode manufactured from a difficult to solder material includes the steps of coating the electrical connection with a braze material, soldering an electrical lead to the electrical connection.

[0019] In one embodiment, the method may also include where the difficult to solder material is stainless steel.

[0020] In one embodiment, the method may also include where the braze material contains copper.

[0021] Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0022] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0023] FIG. 1 illustrates an elevation view of a liquid sensor in accordance with one embodiment.

[0024] FIG. 2 illustrates an enlargement of the sensor end of a liquid sensor in accordance with one embodiment.

[0025] FIG. 3 A illustrates an end face of an electrode assembly in accordance with one embodiment.

[0026] FIG. 3B illustrates a cross section of an electrode in accordance with one embodiment.

[0027] FIG. 4 illustrates a perspective view of an electrode assembly in accordance with one embodiment.

[0028] FIG. 5 illustrates a side view of the electrode assembly of Fig. 4 in accordance with one embodiment.

[0029] FIG. 6 illustrates a view in cross section of a liquid sensor in accordance with one embodiment.

[0030] FIG. 7 illustrates a perspective view of a liquid sensor in accordance with one embodiment.

[0031] FIG. 8A illustrates an electrode assembly and wiring in accordance with one embodiment.

[0032] FIG. 8B illustrates an electrode assembly in accordance with one embodiment.

[0033] FIG. 9 illustrates an electrode in accordance with one embodiment.

[0034] FIG. 10 illustrates a partial electrode assembly in accordance with one embodiment.

[0035] FIG. 11 A illustrates a liquid sensor in a parallel configuration in accordance with one embodiment.

[0036] FIG. 1 IB illustrates a liquid sensor in an independent configuration in accordance with one embodiment.DETAILED DESCRIPTION

[0037] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in this description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0038] Various technologies that pertain to apparatus and methods will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus.

[0039] It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

[0040] Also, it should be understood that the words or phrases used herein should be construed broadly, unless expressly limited in some examples. For example, the terms “including,” “having,” and “comprising,” as well as derivatives thereof, mean inclusion without limitation. The singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term “and / or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term “or” is inclusive, meaning and / or, unless the context clearly indicates otherwise. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Furthermore, while multiple embodiments or constructions may be described herein, any features, methods, steps, components, etc. described with regard to one embodiment are equally applicable to other embodiments absent a specific statement to the contrary.

[0041] Also, although the terms "first", "second", "third" and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present disclosure.

[0042] Also, unless specified or limited otherwise, the terms “mounted”, “connected”, “supported”, and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

[0043] In addition, the term "adjacent to" may mean: that an element is relatively near to but not in contact with a further element; or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Terms “about” or “substantially” or like terms are intended to cover variations in a value that are within normal industry manufacturing tolerances for that dimension. If no industry standard as available a variation of 20 percent would fall within the meaning of these terms unless otherwise stated.

[0044] An embodiment of a liquid sensor 100 can be seen in Figures 1-3. In this embodiment the liquid sensor 100 has an electrode assembly 112 made up of four electrodes 104 arranged to position the measurement faces 308 of each electrode 104 parallel with the measurement face 308 of another electrode 104, which in this embodiment the electrode assembly 112 produce a substantially square shape to the cross section of the sensor end 102 defined by the arrangement of the four electrodes 104, see FIG. 3A and FIG. 3B. The parallel measurement faces 308 are separated by a gap 210. The gap 210 can be uniform or vary between the ends of the measurement faces 308 or along the length of the electrode assembly 112. The gap 210 can be in a range of 0.008 - 0.010 inches, but testing has found a uniform gap 210 of 0.010 inches is preferable in this embodiment. A spacer 408 is used to define the gap 210 and insulate between the measurement faces 308 of the pairs of electrodes 104, see Fig 4 and Fig. 5. The spacer 408 can be an insulating material, such as a dielectric sheet. The spacer 408 and gap 210 are sized to maximize capillary action of the intended fluid. The capillary action reduces the amount of fluid necessary for the liquid sensor 100 to detect a change in a resistance value that signifies the presence of the liquid state or fluid within the gap 210. The gap 210 and the associated capillary action can be adjusted to accommodate different fluids which may have different viscosities, density, etc. or liquid sensors 100 used in different environments.

[0045] One embodiment of the liquid sensor 100 has a sensor body 106 that encloses the portion of the electrode assembly 112 that separates the electrodes 104 with the spacers 408, see Fig. 1 and Fig. 2. The sensor end 102 extends beyond the sensor body 106. A potting material 212 fills in the space between the electrode assembly 112 and the inner cavity of the sensor body 106. The potting material 212 can be any known potting material known in the art including but not limited to high-temperature 2-part silicone, RTV, high-temperature 2-part epoxy (such as Aremco-Bond™ 2315), Duralco™ 4525 or 4461. The spacer 408 can be used to center or position the electrode assembly 112 within the sensor body 106 prior toapplication / inj ection of the potting material 212. The spacer 408 can be attached to the electrode 104 with an adhesive to create the electrode assembly 112 with the predetermined gap 210 along the sensor end 102. Alternatively, a fixture or any other known method can be used to position the electrode assembly 112 within the sensor body 106 prior to application / inj ection of the potting material 212.

[0046] The embodiment of the sensor body 106 seen in Fig. 1 is cylindrical in shape with a mounting feature 110 located on the sensor end 102 of the sensor body 106. The sensor body 106 can be a standard pipe or tube fitting where the mounting feature 110 is a threaded feature such as NPT thread or a flared end compatible with a compression fitting. Alternatively, the sensor body 106 can be shaped to enclose the shape produced by the electrode assembly 112. The electrodes 104 are each individually attached or connected to a sensor wire 806. The connections 808 between each electrode 104 and sensor wire 806 can be enclosed by the sensor body 106 or the end cap 108 that is attached to the opposite end of the sensor body 106 from the sensor end 102, as seen in Fig. 7. In this embodiment the sensor body 106 is a standard or modified NPT pipe nipple (pipe with threaded ends) and the end cap 108 is threaded onto the sensor body 106. The potting material 212 can be added before or after the end cap 108 has been attached to the sensor body 106. If necessary, additional potting material 212 can be inserted into the end cap 108 to seal the gap between the inner cavity of the end cap 108 and the lead 804.

[0047] An end face of the electrode assembly 112 can be seen in FIG. 3 A, this view is substantially equivalent to a cross-sectional view of the electrode assembly 112. One or all of the electrodes 104 can include an identifying feature 322, which in this embodiment is a notch machined into the outward face of an electrode 104. The gap 210 is maintained between all of the measurement faces 308 of each individual electrode 104 of the electrode assembly 112 along the sensor end 102 of the electrode assembly 112. The substantially square shape of the cross-section and or end of the electrode assembly 112 can be seen in FIG. 3A. In this embodiment, the sensor end 102 has four pairs of measurement faces 308 which produces a cross shaped gap 210 where all of the measurement faces 308 are across or adjacent from each other at a center of the electrode assembly 112.

[0048] In the present embodiment, each electrode 104 has a triangular cross section with two measurement faces 308 per electrode 104. Each electrode 104 has an external surface 324 that is not used to create a gap 210 with the measurement face 308 of another electrode 104 in theelectrode assembly 112. In this embodiment the external surface 324 is the exterior surface of each electrode 104 within the electrode assembly 112, see FIG. 1, that is not contained within the sensor body 106 at the sensor end 102. The sensor end 102 is designed to be in contact with the fluid that is being detected, such that the fluid can enter the gap 210 via capillary action or being submerged.

[0049] FIG. 4 and FIG. 5 show an embodiment of an electrode assembly 112 that includes a connection relief 426 that is machined into each electrode 104. The connection relief 426 allows for the connection 808 to each individual electrode 104 to be located within the cross section of the connection relief 426 seen in FIG. 5. The connection relief 426 prevents contact between the connection 808 and the sensor body 106 and allows for the potting material 212 to fill the space between the connection 808 and the inner diameter of the sensor body 106. In this embodiment the spacer 408 or insulator is a rectangular sheet and extends beyond the surface of the connection relief 426 preventing contact between the connections 808 or sensor wires 806 prior to application of the potting material 212 or in embodiments that do not utilize potting material 212. The spacers 408 can be seen as hidden lines in FIG. 4, the gap 210 is created by the absence of the spacers 408 in the sensor end 102 of the electrode assembly 112.

[0050] The spacers 408 have a spacer length 518 and the spacers 408 cover the measurement faces 308 within the spacer length 518. In an embodiment the spacers 408 can be four identical rectangular shaped sheets of material. In another embodiment the spacers 408 can be one large spacer that covers two measurement faces 308, as seen in FIG. 10 and a pair of smaller spacers 408 that cover the remaining measurement faces 308.

[0051] FIG. 6 shows a partial cross section of a liquid sensor 100. The sensor body 106 of the liquid sensor 100 has a first internal cavity 620 sized to contain the electrode assembly 112 and accommodate a potting material 212 between the sensor body 106 and the first internal cavity 620. The second internal cavity 622 is configured to enclose a lead 804 which is a cable that contains the sensor wires 806 from each of the electrodes 104.

[0052] FIG. 7 is the electrode assembly 112 of FIG. 8B within a sensor body 106 and end cap 108 with potting material 212 between the electrode assembly 112 and sensor body 106.

[0053] In the present embodiment, each electrode 104 in the electrode assembly 112 has a connection 808 to a sensor wire 806, see FIG. 8A. The connection 808 can be any know method of attaching conductors, such as soldering, brazing, mechanical tab, conductive adhesive or welding. In one embodiment the electrodes 104 are manufactured from stainlesssteel, such as a 300 series stainless steel, which are known to be difficult to solder using conventional methods. In embodiments where the electrodes 104 are stainless steal the connection 808 is created by first coating or brazing the connection end of the electrode 104 with Silicon Bronze material. In the present embodiment, TIG (Tungsten Inert Gas) brazing is used to apply the Silicon Bronze material to the connection end of the electrodes 104 by only melting the braze material without melting the base material of the electrodes 104. Other heat sources can be used to accomplish the brazing process, such as Oxy-acetylene brazing, furnace brazing or any other method known in the art. Once coated, the components of the braze material, such as copper, allow for conventional soldering of sensor wires 806 at the connections 808. Each of the sensor wires 806 are contained within an insulated lead 804 which is connected to the measurement equipment (not shown).

[0054] As seen in FIG. 9, each electrode 104 has an overall electrode length 906.

[0055] In FIG. 10 a partial electrode assembly 112 can be seen that consists of two electrodes 104 stacked on top of one another such that one of the measurement faces 308 of each electrode 104 is facing a measurement face 308 of the other electrode 104. The electrodes 104 are separated by the gap 210, which in this embodiment is created by a spacer 408 inserted between the measurement faces 308 of the electrodes 104 along the insulated end 1006 of the electrodes 104, thereby creating the gap 210 at the sensor end 102. In this embodiment three spacers 408 are used to manufacture the electrode assembly 112. A smaller spacer 408 is used to separate the stacked electrodes 104 seen in FIG. 10, and the larger spacer 408 or piece of dielectric 1004 (two electrode sized sheet) is used to separate an opposite stack of electrodes 104. Any configuration can be used to insulate the electrodes 104 at the insulated ends 1006 and create the gap 210 at the sensor end 102. Any known dielectric or insulating material known in the art can be use, as well as any known method of application such as a sheet, paste, etc. In the present embodiment a sheet of mica is used as the dielectric 1004 and or spacer 408. The mica sheet can have a pre applied adhesive or an adhesive can be applied to the dielectric 1004, spacer 408 or the electrode 104. In high temperature applications, such as within steam turbines, high temperature adhesives can be used, such as PermabondK820.

[0056] The measurement faces 308 of each electrode 104 are designed to increase the surface area of each measurement set. Wherein each measurement set comprises the opposing measurement faces 308 of at least two independent electrodes 104. The measurement faces 308 of the embodiments seen in figures 1-5 are substantially rectangular in shape, in totality and inthe region of the sensor end 102. In rectangular electrodes 104 surface area can be increased by increasing the length and or width of the electrode 104. In the present embodiment, the surface area of the sensor end 102 of one measurement face 308 of an electrode 104 is 0.16 in2, the surface area of a measurement set is 0.32 in2, and each electrode assembly 112 has 1.25 in2of surface area. Increasing the surface area has the effect of increasing the sensitivity of the liquid sensor 100. The measured resistance of a liquid sensor 100 with 1-5 total inches of surface area that is used in very clean or non-conductive water would be in tens of Kohms or less.

[0057] The presence of a low conductivity or high resistance liquid can be detected by the change in the resistance value measured between two electrodes 104. The resistance measured by a liquid sensor 100 when there is an air gap or in the presence of a vapor, such as steam, would be a factor of 100 greater than the resistance value that would be measured by the same liquid sensor 100 in the presence of a liquid with low electrical conductively. The sensitivity of the liquid sensor 100 can be increased to obtain a more precise value of the resistance of the liquid with low electrical conductivity if desired. The in one embodiment, the precision of the liquid sensor 100 is designed to accurately detect the presence of the liquid with low electrical conductivity while minimizing the chance of a false reading. For example, with a factor of 100 between an air gap resistance value and presence of liquid resistance value the liquid sensor 100 can be used a detection sensor with high accuracy.

[0058] In many applications access to the measurement locations is limited and increasing the physical dimensions of the electrodes 104 may not be possible, alternative methods of increasing surface area can include drilling holes in the sensor end 102 of the electrodes 104. Alternatively, shapes or patterns can be machined into the measurement face 308 of the electrodes 104 to increase surface area between measurement sets, such as cross-hatching knurling, or other known method in the art. Additional embodiments that use alternative materials, other than machined stainless steel, can be manufactured to increase surface area. Examples include conductive foams, porous metals, wire meshes, fabrics woven with a small percentage of conductive threads.

[0059] In the present embodiment the measurement faces 308 of the electrodes 104 have a surface finish of 1-2 um Ra. A rougher surface finish of the measurement faces 308 can be used to increase the effective surface area of each measurement set.

[0060] As seen in FIG. 3A, the electrodes 104 are separated by a gap 210 from electrodes 104 at either side of an electrode 104. There is a diagonal length of the gap 210 between theelectrodes 104 that are directly across from one another which is larger than the gap 210 between the parallel measurement faces 308. When sufficient liquid fills the gap 210, a resistance can be measured between the electrodes 104. FIG. 1 1 A represents a parallel wiring configuration of a liquid sensor 100. In this embodiment, the measurement sets are configured such that each electrode 104 represented by letters A-D is paired or wired in parallel with the electrode 104 that is not adjacent to it, for example A-C and B-D. The parallel configuration produces two nodes A and B across which a resistance can be measured.

[0061] FIG. 1 IB represents an independent wiring of a liquid sensor 100. In this embodiment, the measurement sets or nodes are configured such that each electrode 104 represented by letters A-D is independently wired with produces fours measurement sets, A, B, A', and B' across which a resistance can be measured.

[0062] Although various embodiments that incorporate disclosed concepts have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these disclosed concepts. Disclosed embodiments are not limited to the specific details of construction and the arrangement of components set forth in the description or illustrated in the drawings. Disclosed concepts may be implemented by other implementations, and of being practiced or of being carried out in various ways, which now would become apparent to one skilled in the art.

[0063] None of the description in the present application should be read as implying that any particular element, step, act, or function is an essential element, which must be included in the claim scope: the scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke a means plus function claim construction unless the exact words "means for" are followed by a participle.

Claims

CLAIMSWhat is claimed is:

1. A liquid sensor for use with a fluid with low electrical conductivity, comprising: a plurality of electrodes configured to have a first end and a second end, a spacer defining a predetermined gap between each of the plurality of electrodes, the spacer insulates between each of the plurality of electrodes, a plurality of sensor wires, one of the plurality of sensor wires attached to one of the plurality of electrodes, each of the plurality of electrodes comprising at least one measurement face, wherein the at least one measurement face of any one of the plurality of electrodes is configured in a measurement pair with another of the at least one measurement face of any other one of the plurality of electrodes, the measurement pair configured to be separated by the predetermined gap, and a resistance value can be measured between the measurement pair.

2. The liquid sensor for use of claim 1, wherein the spacer is a dielectric.

3. The liquid sensor for use of claim 1 wherein the liquid sensor can detect resistance in fluids with conductivities of at least 0.2pS / cm.

4. The liquid sensor for use of claim 1 wherein the liquid sensor can detect a resistance value of deionized water.

5. The liquid sensor for use of claim 1 wherein the liquid sensor can operate in corrosive and or high temperature environments.

6. The liquid sensor for use of claim 1, wherein the at least one measurement face further comprises a surface area.

7. The liquid sensor for use of claim 6, wherein the surface area is 0.016 in2.

8. The liquid sensor for use of claim 1 produces a measurement that is at or below 1 Mohm.

9. The liquid sensor for use of claim 1, wherein the predetermined gap is between a range of0.008" and 0.010".

10. The liquid sensor for use of claim 9, wherein the predetermined gap is 0.010".11 . The liquid sensor for use of claim 1, further comprising a sensor body wherein at least a portion of the liquid sensor is enclosed within the sensor body.

12. The liquid sensor for use of claim 11, further comprising a potting material wherein the potting material fills in a gap between the sensor body and the liquid sensor.

13. A method of soldering an electrical connection of an electrode manufactured from a difficult to solder material comprising the steps of: coating the electrical connection with a braze material, soldering a sensor wire to the electrical connection.

14. The method of claim 13, wherein the difficult to solder material is stainless steel.

15. The method of claim 13, wherein the braze material contains copper.

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