WO2009055258A2

WO2009055258A2 - Ionic probe

Info

Publication number: WO2009055258A2
Application number: PCT/US2008/079480
Authority: WO
Inventors: John Robert Woodward; Leon Moore; Russell Martin Young
Original assignee: Hach Company
Priority date: 2007-10-22
Filing date: 2008-10-10
Publication date: 2009-04-30
Also published as: WO2009055258A3

Abstract

An ionic probe (104) is provided according to the invention. The ionic probe (104) includes a unitary outer shell (203) including a proximal end (201) and a distal end (202). At least one active electrode (230) and at least one reference electrode (235) are located within the outer shell (203). The ionic probe (104) further includes a closed end (204) closing the proximal end (201), with the closed end (204) being continuous with the outer shell (203).

Description

IONIC PROBE

Background of the Invention

1. Field of the Invention

The invention is related to the field of an ionic probe. 2. Statement of the Problem

A measure of the ionic level of a fluid is desirable in many situations, including testing of fluids in manufacturing settings, for pharmaceutical production, food processing and/or food quality, water quality testing, etc. Measurement of an ionic level or activity can indicate completion of a reaction, indicate fractions of components, etc. One measure can comprise a measure of a pH level, which comprises a measure of acidity of the fluid being tested. The pH measurement can indicate the acidic or basic condition or level of the fluid.

A pH measurement comprises a measurement of hydrogen ions in a solution, expressed as a logarithmic number between about zero and fourteen (sometimes extending into negative numbers for exceedingly acidic solutions). On the pH scale, a very acidic solution has a low pH value, such as zero or one, corresponding to a large concentration of hydrogen ions (H ⁺ ). In contrast, a very basic solution has a high pH value, corresponding to a very small number of hydrogen ions (or to a correspondingly large number of OH ^" ions). A neutral solution, such as substantially pure water, has a pH value of about seven.

A pH measurement probe typically includes an active electrode and a reference electrode. The active electrode is encased in a chamber that allows ionic exchange with a fluid being tested. The reference electrode is typically included in a separate chamber and solution, also in ionic communication with the fluid being tested. A voltage potential between the two electrodes is thereby formed, similar to a battery. The voltage potential that is developed between the electrodes is directly related to the ion concentration of the solution. The reference electrode provides a stable potential against which the measuring electrode can be compared. The voltage potential can be processed according to a table, formula, or other algorithm to arrive at an ionic concentration measurement, such as a pH value, for example. A prior art pH probe is typically formed of a glass shell that includes a pH sensitive glass region formed into the glass shell. The glass shell is brittle and can be broken if handled roughly or impacted. The prior art glass shell typically comprises blown glass, including hand blown glass. The prior art pH probe is therefore difficult and time-consuming to make and as a result is relatively expensive. The prior art pH probe may require difficult tolerances that must be achieved. The prior art pH probe may include multiple portions and multiple seals that need to be assembled, providing multiple potential leakage avenues. The prior art pH probe may be delicate and easily damaged, as previously noted. Summary of the Invention

An ionic probe is provided according to the invention. The ionic probe comprises a substantially unitary outer shell including a proximal end and a distal end. At least one active electrode and at least one reference electrode are located within the outer shell. The ionic probe further comprises a closed end that substantially closes the proximal end. The closed end is substantially continuous with the outer shell. An ionic probe is provided according to the invention. The ionic probe comprises a substantially unitary outer shell including a proximal end and a distal end and a closed end that substantially closes the proximal end. The closed end is substantially continuous with the outer shell. The ionic probe further comprises one or more internal non-circular partitions dividing up an internal volume of the ionic probe into two or more chambers. One or more active electrodes are located in the two or more chambers and are configured to generate one or more corresponding ionic measurement signals. One or more reference electrode units are located in the two or more chambers not occupied by the one or more active electrodes. The one or more reference electrode units are configured to generate one or more reference signals.

An ionic probe is provided according to the invention. The ionic probe comprises a substantially unitary outer shell including a proximal end, a distal end, and a closed end that substantially closes the proximal end. The closed end is substantially continuous with the outer shell. The ionic probe further comprises one or more ion sensitive regions formed in the closed end and corresponding to one or more active electrodes located within the outer shell. The ionic probe further comprises two or more ion bridges formed in the closed end. The two or more ion bridges correspond to and are in ionic communication with two or more reference electrode units located within the outer shell and partitioned off from the one or more active electrodes.

An ionic probe is provided according to the invention. The ionic probe comprises a substantially unitary outer shell including a proximal end and a distal end and a closed end that substantially closes the proximal end. The closed end is substantially continuous with the outer shell. The ionic probe further comprises a plurality of internal partitions dividing up an internal volume of the ionic probe into a plurality of chambers and two reference electrode units located in two chambers of the plurality of chambers and configured to generate two reference signals. ASPECTS

One aspect of the invention includes, an ionic probe, comprising: a substantially unitary outer shell including a proximal end and a distal end, wherein at least one active electrode and at least one reference electrode are located within the outer shell; and a closed end substantially closing the proximal end, with the closed end being substantially continuous with the outer shell.

Preferably, the ionic probe further comprises one or more internal partitions that divide up an internal volume of the ionic probe into two or more chambers.

Preferably, the ionic probe with the two or more chambers comprises two or more non-coaxial chambers.

Preferably, the ionic probe with the two or more chambers comprises two or more non-circular chambers.

Preferably, the ionic probe further comprising two or more ion sensitive regions formed in the closed end and two or more corresponding active electrodes positioned inside the outer shell and adjacent to the two or more ion sensitive regions.

Preferably, the ionic probe further comprising two or more ion bridges formed in the closed end and two or more corresponding reference electrode units positioned inside the outer shell and in ionic communication with the two or more ion bridges.

Preferably, the ionic probe further comprising two or more ion bridges formed in the closed end and two or more corresponding reference electrode units positioned inside the outer shell and in ionic communication with the two or more ion bridges, with a reference electrode unit of the two or more reference electrode units comprising a glass container, an ion sensitive region formed in a portion of the glass container, and a reference electrode located within the glass container.

Preferably, the ionic probe further comprises four internal partitions that form four chambers. Preferably, the ionic probe further comprises four internal partitions that form four chambers, with two chambers including active electrodes and with two chambers including reference electrode units.

Preferably, the ionic probe further comprises an open distal end and one or more divider seals that substantially seal the distal end. Preferably, the ionic probe further comprising one or more projections formed on the closed end.

Another aspect of the invention comprises an ionic probe, comprising: a substantially unitary outer shell including a proximal end and a distal end; a closed end substantially closing the proximal end, with the closed end being substantially continuous with the outer shell; one or more internal non-circular partitions dividing up an internal volume of the ionic probe into two or more chambers; one or more active electrodes located in the two or more chambers and configured to generate one or more corresponding ionic measurement signals; and one or more reference electrode units located in the two or more chambers not occupied by the one or more active electrodes, with the one or more reference electrode units being configured to generate one or more reference signals.

Preferably, the ionic probe with the two or more chambers comprises two or more non-coaxial chambers. Preferably, the ionic probe with the two or more chambers comprises two or more non-circular chambers.

Preferably, the ionic probe further comprising one or more ion sensitive regions formed in the closed end and the one or more corresponding active electrodes being positioned inside the outer shell and adjacent to the one or more ion sensitive regions. Preferably, the ionic probe further comprising one or more ion bridges formed in the closed end and the one or more corresponding reference electrode units being positioned inside the outer shell and in ionic communication with the one or more ion bridges.

Preferably, the ionic probe with a reference electrode unit of the one or more reference electrode units comprising a glass container, an ion sensitive region formed in a portion of the glass container, and a reference electrode located within the glass container.

Preferably, the ionic probe further comprises an open distal end and one or more divider seals that substantially seal the distal end.

Preferably, the ionic probe further comprises one or more projections formed on the closed end.

Another aspect of the invention comprises an ionic probe, comprising: a substantially unitary outer shell including a proximal end and a distal end; a closed end substantially closing the proximal end, with the closed end being substantially continuous with the outer shell; one or more ion sensitive regions formed in the closed end and corresponding to one or more active electrodes located within the outer shell; and two or more ion bridges formed in the closed end, with the two or more ion bridges corresponding to and in ionic communication with two or more reference electrode units located within the outer shell and partitioned off from the one or more active electrodes.

Preferably, the ionic probe with the one or more ion sensitive regions comprising two or more ion sensitive regions formed in the closed end and two or more corresponding active electrodes positioned inside the outer shell and adjacent to the two or more ion sensitive regions. Preferably, the ionic probe with a reference electrode unit of the two or more reference electrode units comprising a glass container, an ion sensitive region formed in a portion of the glass container, and a reference electrode located within the glass container. Preferably, the ionic probe further comprises four internal partitions that form four chambers.

Preferably, the ionic probe further comprises four internal partitions that form four chambers, with two chambers including active electrodes and with two chambers including reference electrode units. Preferably, the ionic probe further comprises an open distal end and one or more divider seals that substantially seal the distal end.

Another aspect of the invention comprises an ionic probe, comprising: a substantially unitary outer shell including a proximal end and a distal end; a closed end substantially closing the proximal end, with the closed end being substantially continuous with the outer shell; a plurality of internal partitions dividing up an internal volume of the ionic probe into a plurality of chambers; and two reference electrode units located in two chambers of the plurality of chambers and configured to generate two reference signals.

Preferably, the ionic probe with the plurality of chambers comprises four chambers.

Preferably, the ionic probe with the plurality of chambers comprises four non- coaxial chambers.

Preferably, the ionic probe with the plurality of chambers comprises four non- circular chambers.

Preferably, the ionic probe further comprises two ion sensitive regions formed in the closed end and corresponding to two active electrodes. Preferably, the ionic probe further comprises two ion bridges formed in the closed end and corresponding to the two reference electrode units. Preferably, the ionic probe further comprising two ion bridges formed in the closed end and corresponding to the two reference electrode units, with a reference electrode unit of the two or more reference electrode units comprising a glass container, an ion sensitive region formed in a portion of the glass container, and a reference electrode located within the glass container.

Preferably, the ionic probe further comprises one or more projections formed on the closed end. Description of the Drawings

The same reference number represents the same element on all drawings. It should be understood that the drawings are not necessarily to scale.

FIG. 1 shows an ion meter according to an embodiment of the invention.

FIG. 2 shows an ionic probe according to an embodiment of the invention. FIG. 3 is a graph representing first and second reference signals according to an embodiment of the invention.

FIG. 4 is a longitudinal cross-section AA of the ionic probe according to an embodiment of the invention.

FIG. 5 is a transverse cross-section BB of the ionic probe according to an embodiment of the invention.

FIG. 6 is a flowchart of a method for measuring an ionic characteristic of an external test fluid. Detailed Description of the Invention

FIGS. 1-6 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents. FIG. 1 shows an ion meter 100 according to an embodiment of the invention. The ion meter 100 includes an ionic probe 104, a meter electronics 102, and a cable 105 connecting the ionic probe 104 to the meter electronics 102. The ionic probe 104 can include a test end 107. In use, the ionic probe 104 is placed in an external test fluid. The test end 107 is contacted to or immersed in the external test fluid, although the entire ionic probe 104 can be immersed. The external test fluid can comprise water, for example, although it should be understood that various other fluids can be tested. The ionic probe 104 generates a voltage signal that is transferred to the meter electronics 102 by the cable 105. The voltage signal generated by the ionic probe 104 is related to an ion level or ion concentration within the external test fluid.

The meter electronics 102 receives the voltage signal from the ionic probe 104 and processes the signal in order to obtain an ionic measurement, such as a pH value, for example. The processing can include comparing the voltage signal to at least one reference signal, wherein the ionic measurement can be determined from a variation between the voltage signal and the reference signal. Therefore, it is important that the reference signal be steady and continuous in order to serve as a basis for all ionic measurements. If the reference signal is not steady and constant, the resulting ionic measurement will be inaccurate. In the prior art, accuracy of the reference signal is ensured by routine maintenance of the meter. Typically, a prior art pH meter is removed from service and shipped to a service facility for testing and calibration. At the service facility, the pH meter is operated with a known calibration fluid. The known calibration fluid is used to determine whether the meter device is functioning properly and within tolerances. Adjustment of the generated ionic measurement can be performed if the meter in question does not properly measure the known calibration fluid. A service facility will adjust the meter reading according to the response to the calibration fluid.

Taking a meter out of service and returning it to a service facility is inconvenient. In addition, a replacement meter may need to be obtained for the duration. Further, the calibration process is costly.

Advantageously, the ionic probe 104 according to the invention includes at least two reference electrodes and generates at least two reference signals. The at least two reference signals can be used to perform self-calibration within the ion meter 100 (see FIG. 2 and the accompanying discussion and see FIG. 6 and the accompanying discussion).

Another advantage is that the ionic probe 104 according to the invention is formed of an at least partially resilient material. In some embodiments, the outer components of the ionic probe 104 can be formed of a plastic material. Consequently, the ionic probe 104 can withstand impacts, scrapes, compression, and other potential failure causes. The resilient material provides a lower cost ionic probe 104 and enables quicker, cheaper, and less difficult manufacturing of the ionic probe 104. FIG. 2 shows the ionic probe 104 according to an embodiment of the invention.

The ionic probe 104 in this embodiment includes a unitary outer shell 203 including a proximal end 201 and a distal end 202. The ionic probe 104 further includes a closed end 204 that substantially closes the proximal end 201 of the outer shell 203. The closed end 204 is substantially continuous with the outer shell 203, requiring no seals or other closure members.

The outer shell 203 is substantially unitary in nature, being formed of a continuous material from the proximal end 201 to the distal end 202 and including the closed end 204. Alternatively, the closed end 204 can be bonded, welded, or otherwise joined to the outer shell 203. Because the outer shell 203 is unitary, it does not comprise multiple components joined together with seals. As a result, the ionic probe 104 according to any embodiment of the invention is less prone to leakage. This produces a more reliable and accurate ionic probe 104.

The outer shell 203 creates a more robust ionic probe 104. The outer shell 203 can be formed of an at least partially flexible material, such as plastic, for example. As a result, the ionic probe 104 can absorb impacts and retain structural integrity. In addition, the material of the outer shell 203 can cushion impacts and reduce likelihood of damage to the internal components, including a glass container 233 of a reference electrode unit 234 (see FIG. 4).

Another advantage is that manufacturing of the ionic probe 104 is improved. For example, the number of components and the number of manufacturing steps can both be reduced. Consequently, the assembly process is simplified. The material used to construct the ionic probe 104 can be less costly to purchase and form into shape. Glass blowing or forming is not required. Fewer sealing elements are required.

The outer shell 203 can comprise a substantially cylindrical shape, as shown. However, it should be understood that the outer shell 203 and the ionic probe 104 can comprise any desired shape, including oval, rectangular, or even irregular in cross- section, for example.

The closed end 204 includes a plurality of openings 207 in the outer shell 203. However, these openings 207 are sealed during manufacture and do not allow fluid inside the outer shell 203. In addition, the distal end 202 is sealed, such as by a divider seal(s) 208 (see FIG. 4, for example).

At least two ion bridges 214 and one or more ion sensitive regions 217 can be affixed and sealed to the closed end 204 of the ionic probe 104 and seal the corresponding openings 207. At least two ion bridges 214 and one or more ion sensitive regions 217 can be affixed and sealed to the closed end 204 in any suitable manner, including by adhesives or bonding agents, by any manner of welding, melting, or heat sealing, etc. It should be understood that although the ion sensitive regions 217 are shown as being at an end of the ionic probe 104, alternatively they can be located on a side region. It should be understood that other junctions or sensors may occupy the openings 207 and may be of different sizes, as required. The at least two ion bridges 214 and the one or more ion sensitive regions 217 advantageously allow electrode redundancy. For example, two or more ion sensitive regions 217 can be built into the ionic probe 104. If one of the two or more ion sensitive regions 217 appears to be reading incorrectly, the erroneous or suspect active electrode unit can be ignored. Likewise, the at least two ion bridges 214 can comprise multiple reference electrode units that can allow a reference electrode unit to be disregarded if erroneous outputs are received.

Further, the ionic probe 104 can be constructed so that a cover or obstructing layer exists over one or more of the ion bridges 214 and/or the ion sensitive regions 217. Consequently, the cover or obstructing layer can be broken off or removed at any time, enabling a new active or reference unit to be brought into use.

The active ion sensitive region 217 extends from the proximal end 201 of the ionic probe 104 and is designed to contact the external test fluid. The active electrode 230 resides in an active chamber 227 (see FIG. 4) located at least partially at the proximal end 201 of the outer shell 203. As a result, the active electrode 230 is adjacent to an inner surface of the active ion sensitive region 217 and is in ionic communication with the active ion sensitive region 217. A voltage potential is generated on the active electrode 230 as a result of ion interaction at the active ion sensitive region 217. The active ion sensitive region 217 and the reference ion sensitive region 232 (see FIG. 4) form an ionic circuit, similar to a battery. It should be understood that some or all of the ionic probe 104 may be immersed in the external test fluid, as previously noted.

The active ion sensitive region 217 allows ion exchange at the outer ion sensitive area of the electrode. There is a substantially constant charge on the inner surface of the ion sensitive material. This allows the development of a potential difference between an external test fluid and the active electrode 230. The magnitude of this potential is dependent on the ionic value of the solution, such as the pH value, for example. The same is true of the reference ion sensitive region 232. A millivolt potential is created across the interface between an ion sensitive region 217 and the external aqueous solution. The magnitude of this potential is dependent on the pH value of the solution. The ion sensitive region 217 can comprise any manner of ion transmissive material that does not permit a fluid exchange between the inside and the outside of the outer shell 203. For example, the ion sensitive region 217 can be formed of an ion sensitive glass. However, other materials are contemplated and are within the scope of the description and claims.

The one or more ion sensitive regions 217 can comprise a specially formulated pH sensitive lithium ion-conductive glass consisting of the oxides of silica, lithium, calcium, and other elements. The structure of the pH glass allows ionic interaction between the external test fluid and the hydrated layer of the glass 217. The one or more ion sensitive regions 217 can comprise a wafer of predetermined shape, as desired, and of a predetermined thickness. Advantageously, the predetermined thickness can be selected according to pH glass manufacturing techniques and in order to achieve desired ion transfer properties. For example, the thickness of an ion sensitive region 217 can control an ion exchange speed.

Another advantage is that manufacturing and installing the ion sensitive regions 217 according to the invention enables a mass production process. In the prior art, a pH sensitive glass bulb is hand-blown into a glass pH probe body. The prior art pH sensitive glass is adhered to the non-pH glass by melting at high temperatures. This is very costly and time-consuming. In addition, there are opportunities for quality problems through such a complex process and the prior art is highly dependent on trained and skilled glass artisans.

In contrast, the ion sensitive region 217 according to the invention can be glued or otherwise bonded in place. Advantageously, this enables a cheaper, simpler, more reproducible, and faster pH probe production. Thickness of the ion sensitive region 217 can be controlled and uniformity can be ensured. In the embodiment shown, the ionic probe 104 includes two ion sensitive regions

217 and two corresponding active electrodes 230 (see FIG. 4). For example, the two ion sensitive regions 217 can be different and can be designed for different external test fluids. However, the number of ion sensitive regions 217 and active electrodes 230 can be varied as desired, such as where the ion sensitive regions 217 have different properties, such as different ion exchange rates, different thicknesses, different material compositions, etc. Alternatively, the ionic probe 104 can include two or more ion sensitive regions 217 where the corresponding active electrode chambers 227 employ different electrolytes and different electrolyte concentrations, for example, and where the corresponding active electrodes 230 employ different materials, different electrical properties, different physical characteristics, etc.

An ion bridge 214 allows ion exchange and therefore an ionic communication between an external test fluid and an outer solution in an outer reference buffer chamber 238 (see FIG. 4). The ion bridge 214 can comprise any matter of ion transmissive material that does not enable a fluid exchange. For example, the ion bridge 214 can comprise a salt bridge, as previously discussed. However, other materials are contemplated and are within the scope of this description and claims.

A similar ion bridge 214b (see FIG. 4) allows ion exchange and ionic communication between the outer solution in the outer reference buffer chamber 238, an intermediate solution in an inner reference buffer chamber 239, and the reference electrode unit 234. The inner reference buffer chamber 239 includes and holds a reference electrode unit 234. The reference electrode unit 234 includes a glass container 233 including an ion sensitive region 232 and a reference electrode 235. The glass container 233 holds an internal reference solution in contact with the reference electrode 235. The ion sensitive region 232 of the glass container 233 allows ion interaction and ionic communication between the internal reference solution within the reference electrode unit 234 and the intermediate solution within the inner reference buffer chamber 239.

The major problem with combination pH probes having a reference electrode in a reference chamber is in the junction between the internal reference solution and the external fluid. The junction is vital to the function of the reference electrode and to the establishment of an ionic circuit. Clogging or failure of the junction usually leads to very slow and/or erroneous readings. The junction can also allow the contamination of the internal reference solution by the external test fluid. This poisons a prior art reference electrode, rendering a prior art pH probe inaccurate. As a result, the prior art reference electrode commonly has to be replaced after a duration of use. Some manufacturers have attempted to overcome this problem by the employment of multiple junctions and chambers between the prior art reference electrode and the exterior medium. Others have used flowing junctions in which a continuous supply of reference solution is fed to the prior art reference electrode compartment and exits via a small hole or ground glass aperture. This prevents the contamination of the reference solution and the prior art reference electrode. However, it has the disadvantage of requiring additional expensive and complex apparatus for conducting and metering the solution into the prior art reference electrode chamber.

However, the problem is overcome by encasing a reference electrode in a substantially ion-impermeable chamber, such as a glass chamber as shown in the construction in U.S. Patent No. 6,395,158 to King et al., for use in differential pH probes. The reference electrode is immersed in a reference solution held in the impermeable chamber and communicates with the external test fluid via a reference ion sensitive region, similar to that used for the active electrode. Because the reference electrode is encapsulated in the impermeable chamber, there is less likelihood of poisoning and the pH value of the internal reference solution is kept substantially constant. As a result, the measured potential difference between the active electrode and the reference electrode is dependent only upon the ionic or pH value of the external test fluid being measured and the pH of the internal buffer bathing an active electrode. As a result, the reference voltage remains essentially constant over time, regardless of the ionic level or content of the external test fluid, while completing a circuit between a reference electrode and an active electrode. Consequently, an active voltage at the active electrode can be compared to a reference voltage in order to determine a pH level or other ionic level.

Referring again to FIGS. 2 and 4, the ionic probe 104 can include two ion bridges 214a and 214b and two corresponding reference electrode units 234, such as in the embodiment shown in the figure. However, it should be understood that various numbers of ion bridges 214 can be included in the ionic probe 104. The two reference electrode units 234 can be used to self-calibrate the ionic probe 104. As previously discussed, the two reference electrode units 234 can be used to self-calibrate a meter employing the ionic probe 104, such as a pH meter, for example.

The active solution in the active electrode chamber 227 can comprise any suitable solution that can exchange ions with the ion sensitive region 217. The internal reference solution in the glass container 233 of the reference electrode unit 234 can comprise any suitable solution that can exchange ions with the internal surface of the ion sensitive region 232 of the glass container 233. The inner reference solution in the inner reference buffer chamber 239 can comprise any suitable solution that can exchange ions with the outer surface of the ion sensitive region 232 of the glass container 233 and with the ion bridge 214b. The outer solution/gel in the outer reference buffer chamber 238 can comprise any suitable solution that can exchange ions with the ion bridge 214b and with the ion bridge 214.

FIG. 3 is a graph representing first and second reference signals according to an embodiment of the invention. The graph shows a reference signal A and a reference signal B. The erratic line between the two reference signals A and B represents a measurement signal over a long period of time. It should be understood that for a single test fluid, the measurement signal should be relatively constant and an erratic signal is shown for clarity. It can be seen from the figure that a measurement value can be obtained from a comparison of the measurement signal to one or both of the reference signals A and B. For example, where the reference signal A is generated for a reference buffer of a first pH value and where the reference signal B is generated for a reference buffer of a second pH value, then the measurement signal can be compared to the reference signals and the measurement value can be determined according to a predetermined algorithm. The algorithm can perform any manner of correlation, extrapolation, interpolation, etc. It should be understood that only one reference signal is required in order to obtain the measurement signal. However, it should be apparent that the ionic measurement value determination will be easier and will be more accurate in the presence of at least two reference signals. More than two reference signals can be employed, if desired. A further advantage is that two or more reference signals allow and enable the ion meter 100 to be self-calibrating and/or self-compensating. The graph shows a first deviation or bump in the reference signal A. The bump can be caused by various factors, such as temperature changes, clogging of an ion bridge, etc. By comparing the reference signal A and the reference signal B, the bump can be detected and ignored, minimizing or eliminating errors. Consequently, one reference signal can be used to check on the other reference signal(s). The comparison can therefore be used to detect a single reference drift in one of the reference signals.

If both reference signals are diverging from an essentially steady state, then this error condition can also be detected. If both (or two or more) reference signals are diverging in a roughly parallel manner, then they may be indicating some manner of poisoning or contamination of the reference buffers. The comparison can therefore be used to detect a dual reference drift in two reference signals. If the divergence is not excessive, then a computational factor can be derived that can be used to correct the reference signals. In some embodiments, the two or more reference signals can be compared to a predetermined constant, such as a predetermined voltage level. The predetermined constant can be used to determine when the two or more reference signals are diverging from a predetermined expected value.

FIG. 4 is a longitudinal cross-section AA of the ionic probe 104 according to an embodiment of the invention. In addition to the previously recited components, the ionic probe 104 can include one or more internal partitions 223 that create two or more internal chambers 222. The ionic probe 104 further includes an active electrode chamber 227 formed by a divider seal 208a, an active electrode 230 in the active electrode chamber 227, an outer reference buffer chamber 238 formed by a divider seal 208b, an inner reference buffer chamber 239 formed by the divider seal 208b and a divider seal 208c, the reference electrode unit 234, and a reference support chamber 231 formed by the divider seal 208c and a divider seal 208d. The divider seal 208d can hold and support an end of the reference electrode unit 234. The divider seal 208d can further seal the chamber 222b. The ionic probe 104 can further include a divider seal (not shown) that closes the chamber 222a and supports an end of the active electrode 230. Such divider seals complete the end of the outer shell 203 and make the ionic probe 104 substantially fluid tight.

As previously discussed, the ionic probe 104 can include one or more ion sensitive regions 217 and one or more corresponding active electrodes 230. An active electrode 230 can be formed of any material, such as a silver/silver chloride combination, as is known in the art. A portion of the active electrode 230 is sealed within the active electrode chamber 227. In addition, the active electrode chamber 227 includes an active electrolyte solution. As previously discussed, the active electrolyte solution interacts with the inner surface of the ion sensitive glass. The ion sensitive region 217 is in communication with the active electrode chamber 227 and detects the potential difference created by the interaction. Ionic interaction between the external test fluid and the ion selective glass 217 also sets up a potential difference across the ion selective glass 217. Consequently, a voltage potential can be placed on the active electrode 230 by the external test fluid.

The ion bridge 214 and the ion bridge 214b between the outer reference buffer chamber 238 and the inner reference buffer chamber 239 allow ionic communication between the external test fluid and the reference electrode unit 234. As a result, a voltage potential on the reference electrode 235 remains essentially constant over time, regardless of the ionic level or content of the external test fluid, while completing a circuit between the reference electrode 235 and the active electrode 230. Consequently, an active voltage potential at the active electrode 230 can be compared to one or more resulting reference values in order to determine a pH level or other ionic level. In addition, the reference signals can be compared to other standards in order to calibrate the ion meter 100. The distal end 202 of the ionic probe 104 is closed. In some embodiments, the distal end 202 is closed and sealed by one or more divider seals 208, as previously discussed. Alternatively, a solid end portion (including apertures for the electrodes) is joined to the outer shell 203. The solid end portion (not shown) can be bonded, welded, or otherwise joined to the outer shell 203. The electrode apertures can be separately sealed.

In some embodiments, the ionic probe 104 can further include one or more projections 246 that project from the closed end 204. The one or more projections 246 can prevent the one or more ion sensitive regions 217 and/or the at least two ion bridges 214 from being impacted. The one or more projections 246 therefore can protect the working components of the ionic probe 104.

The electrode unit within the inner reference buffer chamber 239 can comprise a glass container 233 including the reference electrode 235. Alternatively, the outer shell 203 can include molded or machined areas capable of holding ion sensitive discs or regions 217.

FIG. 5 is a transverse cross-section BB of the ionic probe 104 according to an embodiment of the invention. The cross-section is located above the closed end 204 and above the divider seal 208b. In this embodiment, the ionic probe 104 includes four internal partitions 223a-223d that create four chambers 222a-222d. The resulting four chambers 222a-222d are employed as two reference electrode chambers 239 and two active electrode chambers 227. It should be understood that other arrangements can be employed. For example, the ionic probe 104 can include more than two reference electrode units 234 and more than two (or just one) active electrodes 230.

The chambers 222 can be of any shape or size. In some embodiments, the chambers 222 are substantially equal in shape and size. In some embodiments, the chambers 222 are substantially non-circular. In some embodiments, the chambers 222 are substantially non-coaxial. In some embodiments, the chambers 222 are substantially sector-shaped.

The four internal partitions 223 in some embodiments can divide the interior of the ionic probe 104 into four sectors, where a sector can be defined as a cross-sectional area that is bounded by any two radii and the arc included between the two radii. The sectors can be substantially equal in size or can comprise different sizes. It should be understood that any number of internal partitions 223 can be included. The internal partitions 223 can form any desired number of chambers. In some embodiments, the internal partitions 223 form at least two reference electrode chamber structures for at least two reference electrodes 235a and 235b. The at least two reference electrodes 235a and 235b can advantageously enable self-calibration of the ionic probe 104 and of the corresponding meter electronics 102.

The internal partitions 223 can advantageously offer internal strengthening to the outer shell 203. The internal partitions 223 can extend fully across the interior of the outer shell 203, as shown, or can extend only partially across. In addition, the internal partitions 223 can extend substantially radially or can be positioned at other angles and not necessarily along a radius of the outer shell 203. Further, where the outer shell 203 is not substantially cylindrical in shape, the internal partitions 223 can differ in size and the resulting chambers 222 can differ in cross-sectional area.

Where the ionic probe 104 includes two reference electrodes 235a and 235b, corresponding glass containers 233a and 233b can hold solutions of different pH values or of different ionic characteristics. For example, the first reference solution can comprise a 4.0 pH solution and the second reference solution can comprise a 7.0 pH solution. It should be understood that any desired pH values can be used, and the above numbers are given for illustration only. FIG. 6 is a flowchart 600 of a method for measuring an ionic characteristic of an external test fluid. The method enables an ionic meter and corresponding ionic probe to perform a self-calibration and/or self-compensation processes. A self-calibration or self-compensation process can detect an error, inconsistency, or change in the readings produced by the ionic meter and can add or subtract a calibration amount in order to ensure the accuracy and consistency of an ionic measurement. In step 601, an ionic meter generates a measurement signal. The measurement signal comprises a measurement related to the ionic characteristic of an external test fluid. In some embodiments, the measurement signal comprises a voltage signal, but it should be understood that other signals can be employed. In step 602, a first reference signal is generated. The first reference signal can be generated by a first reference electrode and/or a first reference electrode unit. In step 603, a second reference signal is generated. The second reference signal can be generated by a second reference electrode and/or a second reference electrode unit.

In step 604, the measurement signal is compared to the first and second reference signals in order to determine an ionic measurement. As a result, given that the first and second reference signals are substantially known ionic values, the ionic measurement can be determined from the measurement signal. The comparison can result in a correlation, extrapolation, or interpolation of the resulting ionic measurement from the initial measurement signal. The comparison can result in a table lookup, formula completion, or other algorithmic solution for the ionic measurement. For example, wherein the first reference signal comprises a relatively low pH value and the second reference signal comprises a relatively high pH value, the ionic measurement can be determined from a relative distance of the ionic measurement signal to the two reference signals. In step 605, a calibration value can be determined from the comparison. The calibration value can comprise a value to be added to or subtracted from an ionic measurement value. For example, after a correlation, extrapolation, or interpolation of the ionic measurement, a calibration value can be determined and used to refine the ionic measurement value. In step 606, a single reference drift amount can be determined from the comparison. For example, one of the reference signals can be compared to the other signal and/or to stored historical values. Any deviation by the reference signal under comparison can be noted and flagged. Any deviation by the reference signal under comparison can be corrected by a non-affected reference signal. For example, if one reference signal goes up or down in value, it can be corrected to maintain a predetermined difference from the other reference signal.

In step 607, a dual reference drift amount can be determined from the comparison. For example, both reference signals can be compared to stored historical values and any significant deviation can be noted and compensated for. In step 608, the first and second reference signals can be compared to a predetermined constant, such as a constant voltage level. Any divergence by one or both of the reference signals can be determined. As before, a diverging reference signal can be corrected by using the predetermined constant.

The ionic probe according to some embodiments can provide a probe that requires fewer components. The ionic probe according to some embodiments can provide a probe that includes fewer avenues for leakage. The ionic probe according to some embodiments can provide a probe that features an easier manufacturing process requiring fewer components, fewer assembly steps, and less demanding tolerances. The ionic probe according to some embodiments can provide a probe wherein cheaper materials can be used. The ionic probe according to some embodiments can provide a probe that uses materials that are less hard and less brittle.

The ionic probe according to some embodiments can provide a probe that uses two reference electrodes, providing a self-calibration capability. The two reference electrodes are glass-encased, providing less electrolyte contamination, a longer life, a lower operating cost, and requiring less maintenance.

Claims

We claim:

1. An ionic probe (104), comprising: a substantially unitary outer shell (203) including a proximal end (201) and a distal end (202), wherein at least one active electrode (230) and at least one reference electrode (235) are located within the outer shell (203); and a closed end (204) substantially closing the proximal end (201), with the closed end (204) being substantially continuous with the outer shell (203).

2. The ionic probe (104) of claim 1, further comprising one or more internal partitions (223) that divide up an internal volume of the ionic probe (104) into two or more chambers (222).

3. The ionic probe (104) of claim 2, with the two or more chambers (222) comprising two or more non-coaxial chambers (222).

4. The ionic probe (104) of claim 2, with the two or more chambers (222) comprising two or more non-circular chambers (222).

5. The ionic probe (104) of claim 1, further comprising two or more ion sensitive regions (217) formed in the closed end (204) and two or more corresponding active electrodes (230) positioned inside the outer shell (203) and adjacent to the two or more ion sensitive regions (217).

6. The ionic probe (104) of claim 1, further comprising two or more ion bridges (214) formed in the closed end (204) and two or more corresponding reference electrode units (234) positioned inside the outer shell (203) and in ionic communication with the two or more ion bridges (214).

7. The ionic probe (104) of claim 1, further comprising two or more ion bridges (214) formed in the closed end (204) and two or more corresponding reference electrode units (234) positioned inside the outer shell (203) and in ionic communication with the two or more ion bridges (214), with a reference electrode unit (234) of the two or more reference electrode units (234) comprising a glass container (233), an ion sensitive region (232) formed in a portion of the glass container (233), and a reference electrode (235) located within the glass container (233).

8. The ionic probe (104) of claim 1, further comprising four internal partitions (223a-223d) that form four chambers (222a-222d).

9. The ionic probe (104) of claim 1, further comprising four internal partitions (223a-223d) that form four chambers (222a-222d), with two chambers (222a, 222c) including active electrodes (230b, 230a) and with two chambers (222b, 222d) including reference electrode units (234a, 234b).

10. The ionic probe (104) of claim 1, further comprising an open distal end (202) and one or more divider seals (208) that substantially seal the distal end (202).

11. The ionic probe (104) of claim 1, further comprising one or more projections (246) formed on the closed end (204).

12. An ionic probe (104), comprising: a substantially unitary outer shell (203) including a proximal end (201) and a distal end (202); a closed end (204) substantially closing the proximal end (201), with the closed end (204) being substantially continuous with the outer shell (203); one or more internal non-circular partitions (223) dividing up an internal volume of the ionic probe (104) into two or more chambers (222); one or more active electrodes (230) located in the two or more chambers (222) and configured to generate one or more corresponding ionic measurement signals; and one or more reference electrode units (234) located in the two or more chambers (222) not occupied by the one or more active electrodes (230), with the one or more reference electrode units (234) being configured to generate one or more reference signals.

13. The ionic probe (104) of claim 12, with the two or more chambers (222) comprising two or more non-coaxial chambers (222).

14. The ionic probe (104) of claim 12, with the two or more chambers (222) comprising two or more non-circular chambers (222).

15. The ionic probe (104) of claim 12, further comprising one or more ion sensitive regions (217) formed in the closed end (204) and the one or more corresponding active electrodes (230) being positioned inside the outer shell (203) and adjacent to the one or more ion sensitive regions (217).

16. The ionic probe (104) of claim 12, further comprising one or more ion bridges (214) formed in the closed end (204) and the one or more corresponding reference electrode units (234) being positioned inside the outer shell (203) and in ionic communication with the one or more ion bridges (214).

17. The ionic probe (104) of claim 12, with a reference electrode unit (234) of the one or more reference electrode units (234) comprising a glass container (233), an ion sensitive region (232) formed in a portion of the glass container (233), and a reference electrode (235) located within the glass container (233).

18. The ionic probe (104) of claim 12, further comprising an open distal end (202) and one or more divider seals (208) that substantially seal the distal end (202).

19. The ionic probe (104) of claim 12, further comprising one or more projections (246) formed on the closed end (204).

20. An ionic probe (104), comprising: a substantially unitary outer shell (203) including a proximal end (201) and a distal end (202); a closed end (204) substantially closing the proximal end (201), with the closed end (204) being substantially continuous with the outer shell (203); one or more ion sensitive regions (217) formed in the closed end (204) and corresponding to one or more active electrodes (230) located within the outer shell (203); and two or more ion bridges (214) formed in the closed end (204), with the two or more ion bridges (214) corresponding to and in ionic communication with two or more reference electrode units (234) located within the outer shell

(203) and partitioned off from the one or more active electrodes (230).

21. The ionic probe (104) of claim 20, further comprising one or more internal partitions (223) that divide up an internal volume of the ionic probe (104) into two or more chambers (222).

22. The ionic probe (104) of claim 21, with the two or more chambers (222) comprising two or more non-coaxial chambers (222).

23. The ionic probe (104) of claim 21, with the two or more chambers (222) comprising two or more non-circular chambers (222).

24. The ionic probe (104) of claim 20, with the one or more ion sensitive regions (217) comprising two or more ion sensitive regions (217) formed in the closed end (204) and two or more corresponding active electrodes (230) positioned inside the outer shell (203) and adjacent to the two or more ion sensitive regions (217).

25. The ionic probe (104) of claim 20, with a reference electrode unit (234) of the two or more reference electrode units (234) comprising a glass container (233), an ion sensitive region (232) formed in a portion of the glass container (233), and a reference electrode (235) located within the glass container (233).

26. The ionic probe (104) of claim 20, further comprising four internal partitions (223a-223d) that form four chambers (222a-222d).

27. The ionic probe (104) of claim 20, further comprising four internal partitions (223a-223d) that form four chambers (222a-222d), with two chambers (222a, 222c) including active electrodes (230b, 230a) and with two chambers (222b, 222d) including reference electrode units (234a, 234b).

28. The ionic probe (104) of claim 20, further comprising an open distal end (202) and one or more divider seals (208) that substantially seal the distal end (202).

29. The ionic probe (104) of claim 20, further comprising one or more projections (246) formed on the closed end (204).

30. An ionic probe (104), comprising: a substantially unitary outer shell (203) including a proximal end (201) and a distal end (202); a closed end (204) substantially closing the proximal end (201), with the closed end (204) being substantially continuous with the outer shell (203); a plurality of internal partitions (223) dividing up an internal volume of the ionic probe (104) into a plurality of chambers (222); and two reference electrode units (234a, 234b) located in two chambers (222b, 222d) of the plurality of chambers (222) and configured to generate two reference signals.

31. The ionic probe (104) of claim 30, with the plurality of chambers comprising four chambers (222a-222d).

32. The ionic probe (104) of claim 30, with the plurality of chambers comprising four non-coaxial chambers (222a-222d).

33. The ionic probe (104) of claim 30, with the plurality of chambers comprising four non-circular chambers (222a-222d).

34. The ionic probe (104) of claim 30, further comprising two ion sensitive regions (217) formed in the closed end (204) and corresponding to two active electrodes (230a,

230b).

35. The ionic probe (104) of claim 30, further comprising two ion bridges (214) formed in the closed end (204) and corresponding to the two reference electrode units (234a, 234b).

36. The ionic probe (104) of claim 30, further comprising two ion bridges (214) formed in the closed end (204) and corresponding to the two reference electrode units (234a, 234b), with a reference electrode unit (234) of the two or more reference electrode units (234) comprising a glass container (233), an ion sensitive region (232) formed in a portion of the glass container (233), and a reference electrode (235) located within the glass container (233).

37. The ionic probe (104) of claim 30, further comprising an open distal end (202) and one or more divider seals (208) that substantially seal the distal end (202).

38. The ionic probe (104) of claim 30, further comprising one or more projections (246) formed on the closed end (204).