WO2003074998A1 - Fluid presence and qualitative measurements by transient immitivity response - Google Patents
Fluid presence and qualitative measurements by transient immitivity response Download PDFInfo
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- WO2003074998A1 WO2003074998A1 PCT/US2002/036921 US0236921W WO03074998A1 WO 2003074998 A1 WO2003074998 A1 WO 2003074998A1 US 0236921 W US0236921 W US 0236921W WO 03074998 A1 WO03074998 A1 WO 03074998A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
- G01N27/221—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance by investigating the dielectric properties
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
- G01N27/228—Circuits therefor
Definitions
- the present invention relates to a process for measuring the presence and various qualities of fluids, and materials containing fluids. More specifically, the present invention describes a process for detecting minute compositional changes in single sampling or continuous flow monitoring of fluids which offers extreme sensitivity, simplified temperature compensation, probe design, materials and control electronics.
- a myriad of fluids are used in many scientific and industrial processes, as well as in end user applications. Initial, in-process and in-use testing of these fluids can often help prevent potential problems. Many processes rely on precise mixtures of fluids, slurries, suspensions or wetted materials and require accurate feedback on the resultant mixtures. End users often depend on accurate compositions of fluids, slurries, suspensions or wetted materials for safe and efficient use. Qualitative measurement of these materials can often prevent costly mistakes, damage or injury.
- In-use or in-process controls often require sensors capable of properly handling varying levels of flow, pressure and temperature while accurately measuring compositional changes.
- Current methods of measuring the dielectric constant or conductance of a fluid require either a very small range of variance in any of these effects, or extreme and technically complex compensations for them.
- the dielectric constant of fluids is a common qualitative measure associated with fluids. It is known that the dielectric constant in solids is a measure of the ability of molecules to polarize or shift their internal charges in response to external fields. In fluids, the molecules are also able to move about, rotating to orient in a field and/or migrating within the fluid. In electronic terms, the dielectric constant is the analog of a capacitor.
- Conductivity is another common measure used to produce a qualitative indication of fluid compositions and charged species in a fluid.
- Charged species, or ions, present in a fluid provide a means for the passage of electrons through a fluid. The more ions present, the lower the electrical resistance of the fluid and the greater the magnitude of current that can flow through the fluid. In electronic terms this phenomenon is the analog of a resistance.
- Electrochemical reactions caused by the introduction of an electrical current into a fluid can cause electrode corrosion and contamination.
- Sensed voltages or currents often need amplification and signal conditioning to provide suitable readings.
- the present invention relates to a process for measuring the presence and various qualities of fluids and materials containing fluids. It offers improved performance over previous methods in its range and sensitivity, as well as relative insensitivity to temperature and fluid flow. In addition, this process offers simplified design and measurement.
- the present invention includes a process and an apparatus for controlling and measuring various electrochemical effects of simplified electrochemical cells.
- the underlying effects measured are complex in nature.
- the present invention controls some of the individual influences of those effects to derive a measurement that has advantages over previous techniques and is termed here Transient Immitivity Response (TIR).
- TIR Transient Immitivity Response
- the primary feature of the invention is the use of a capacitance external to the cell to accumulate, control and limit the electrical currents passing through the cell.
- Transient immitivity response refers to the interactions between this capacitance and the current transfer mechanisms within the electrochemical cell. These interactions create a complex rate of electrical charging and discharging of this external capacitance that can be measured in many different ways.
- This capacitance, the cell configuration and other external components may be adjusted to enhance or reduce the effect of various charge transfer mechanisms and to fit the invention to virtually any fluid.
- the transient immitivity response is the time related complex rate at which charge is passed through the cell and accumulated on the external capacitance.
- One embodiment according to the invention includes two electrodes spaced apart from each other and both in contact with a fluid being tested.
- This embodiment includes an excitation source for providing a time-varying excitation voltage to a first one of the electrodes. The excitation voltage is switched between a first defined voltage level and a distinct second defined voltage level.
- the first and second voltage levels are alternatively applied to the first electrode for specific time periods.
- This source has a low source resistance such that it is able to supply sufficient electrical current to change the first electrode's electrical potential in a minimal time and thereby rapidly charge the first electrode's capacitance.
- a defined capacitance is located between the second electrode and an electrical or circuit ground.
- the ground has a defined voltage.
- This embodiment also includes a voltage detector for detecting a sensed voltage induced on the defined capacitance. The sensed voltage is proportional to electrical charges conducted through the fluid from the first electrode to the second electrode as a consequence of the excitation voltage applied to the first electrode.
- This voltage detector has a very high resistance to electrical ground such that there is no substantial current flow through it from the cell. Examples of suitable voltage detectors include current generation FET transistors, op amps and CMOS logic circuits having input resistances greater then 10 n ohms.
- the voltage level at the excitation source is held constant at least until the cell is at equilibrium when a fluid is present. If there is no fluid present, no voltage will be detected at the sensing or detecting means. If a fluid is present at equilibrium, all portions of the electrochemical cell of the embodiment will be at essentially the same voltage as the excitation voltage and the voltage sensed at the second electrode will be essentially equal to the voltage at the first electrode. The excitation voltage of the first means is then switched to a second voltage level. The cell will now work to come to equilibrium at this second voltage level.
- the embodiment further includes a means for determining one or more time intervals between the switch in first and second defined voltage levels and when a sensed voltage at the capacitance attains one or more selected voltage levels. These time intervals represent the transient immitivity response of the fluid. Alternately, this means may measure the voltage attained at the capacitance at one or more predetermined time intervals after the switch in first and second defined voltage levels. Once again, providing a measure of the
- Attained at the second electrode is a time-related function of all of the resistances and capacitances of the electrode interface and the fluid, and the change in voltage of the first excitation source.
- This embodiment is further capable of providing the transient immitivity response as a digital or analog output.
- a lack of a changing sensed voltage may indicate a lack of fluid between the electrodes. While this single time, or rate, measurement embodies the basis for the present invention, two or more measurements of the time-related response of this electrochemical cell system may be used to elucidate more subtle information.
- the present invention is also a method of using an apparatus to obtain a transient immitivity response of a fluid. Initially, first and second electrodes are selected and the electrodes, spaced apart from each other, are brought into contact with a fluid. Time varying excitation voltage is then applied to the first electrode. The excitation voltage is subsequently switched between a first defined voltage level and a distinct second defined voltage level so that the first and second defined levels are alternately applied to the first electrode for specific time periods.
- the excitation source is further characterized by having a low resistance in order for a minimal switch time to exist when the excitation voltage is switched between the first and second defined voltage levels.
- the method further includes providing a defined capacitance between the second electrode and an electrical or circuit ground. The ground has a defined voltage.
- a sense voltage is then detected as having been induced on the capacitance, the sense voltage being proportional to electrical charges conducted through the fluid from the first electrode to the second electrode as a consequence of the excitation voltage applied to the first electrode.
- the detector used is preferably characterized by having a high input resistance to minimize external current flows.
- one or more time intervals are determined between the switch between first and second defined voltage levels and when the sense voltage at the second electrode attains one or more specific voltage levels. Alternately, one or more voltage levels attained at predetermined time intervals from the time the excitation voltage is switched between a first and second defined voltage level may be measured. These time intervals and voltage levels represent the transient immitivity response of the fluid and may be subsequently provided as digital or analog output.
- Fig. 1 is a schematic diagram showing the commonly accepted electronic analogue of a two-electrode electrochemical cell.
- Fig. 2A is a graph showing a characteristic of a change in voltage.
- Fig. 2B is a schematic diagram showing a capacitor.
- Fig. 2C is a graph describing the reaction of the capacitor shown in Fig. 2B to the change in voltage shown in Fig. 2A, and the indirect currents induced by that change.
- Fig. 3 A is a graph showing a characteristic of a change in voltage the same as that shown in Fig. 2A.
- Fig. 3B is a schematic diagram showing a capacitor and resistor connected in parallel.
- Fig. 3C is a graph describing the reaction of the parallel resistance and capacitance (admittance) shown in Fig. 3B to the change in voltage shown in Fig. 3A.
- Fig. 4A is a graph showing a characteristic of a change in voltage the same as that shown in Figs. 2A and 3A.
- Fig. 4B is a schematic diagram showing an admittance with a capacitor connected between the output of the admittance and ground.
- Fig. 4C is a graph that shows the reaction of the admittance to the voltage change of Fig. 4A when the capacitance is placed between the sensing end and electrical ground.
- Fig. 5 is a graph showing the result of a study of the electrical resistance of certain aircraft hydraulic oils over a range of temperatures.
- Fig. 6 is a graph showing the results of measurements of certain aircraft hydraulic oils over a range of temperatures according to a preferred embodiment of the present invention.
- Fig. 7 is a graph of the measurements of a number of aqueous solutions over a range of concentrations, using a preferred embodiment of the present invention.
- Figs. 8A-D are graphs showing the results of a comparison study of the temperature characteristics of various known methods and the present invention on distilled water.
- Figs. 9A-D are graphs showing the results of a comparison study of the temperature characteristics of various known methods and the present invention on tap water.
- Figs. 10A-D are graphs showing the results in Fig. 8A-D and Fig. 9A-D, respectively, in a manner representing the temperature characteristics of these methods in relation to compositional changes.
- Fig. 11 A is a schematic diagram depicting a measurement arrangement according to one embodiment of the present invention.
- Fig. 1 IB is a representative waveform measured by the arrangement of Fig. 11 A.
- Fig. 12A is a schematic diagram depicting a measurement arrangement according to an alternative embodiment of the present invention.
- Fig. 12B is a representative waveform measured by the arrangement of Fig. 12 A.
- Fig. 13A is a schematic diagram depicting a measurement arrangement according to another alternative embodiment of the present invention.
- Fig. 13B shows representative waveforms measured by the arrangement of Fig. 13 A.
- Fig. 14 is a graph showing the results of using the embodiment shown in Fig. 13A to determine the electrical capacitances of a cell.
- Fig. 15 is a schematic diagram depicting a measurement arrangement according to yet another alternative embodiment of the present invention.
- Fig. 16A is a schematic diagram depicting a measurement arrangement according to another alternative embodiment of the present invention.
- Fig. 16B is a representative waveform measured by the arrangement of Fig. 16A.
- Fig. 17A is a schematic diagram depicting a measurement arrangement according to still another alternative embodiment of the present invention.
- Fig. 17B is a representative waveform measured by the arrangement of Fig. 17A.
- Fig. 18A is a schematic diagram depicting a measurement arrangement according to another alternative embodiment of the present invention.
- Fig. 18B is a representative waveform measured by the arrangement of Fig. 18 A.
- Fig. 1 is a schematic providing a known comparative view of electrochemical cell parameters and their electronic analogues relevant to the present invention.
- a two electrode electrochemical cell may be conceptually separated into a first or excitation electrode interface A, a fluid region B, and a second or sensing electrode interface C.
- Fig. 1 generally shows these three regions demarcated by vertical dashed lines. These three regions define a path for electrical current flow between the excitation electrode 1 and sensing electrode 2.
- the fluid region, B has a known capacitance C f arising from atomic and molecular polarization as well as separation of any ionic species present in the fluid.
- the fluid also has a known conductivity, or electrical resistance R f . Together, these two effects can be electrically modeled as a parallel resistance and capacitance, known as an admittance.
- the two electrode interfaces, A and C can also be electrically modeled as admittances. It is known that an electrode-fluid interface has a capacitance due to laminar molecular layers which form between the electrode and the diffuse bulk of the fluid. These are termed the Helmholtz layers, and establish a separation of charges, and thus a capacitance, C ee and C se , similar to two very closely spaced plates of a capacitor. It is also known that the arrangement and capacitance of these layers is dependent on the electrical potentials present, which is not true of normal capacitors. Each electrode interface A and C also has known electrical resistance R ee and R se to current flow.
- Figs. 2 A, 2B and 2C are a representation of the known electrical reaction of a capacitor C to a fast voltage change.
- Fig. 2A shows the electrical waveform 3 being impressed on one side of the capacitor C in Fig. 2B.
- the voltage on the excitation side of the capacitor C will rapidly follow the excitation voltage as long as sufficient current is available to charge the capacitor C in a short time.
- the sensing side that has high (> 10 ohms) resistance and zero capacitance to ground.
- the excitation voltage starts at a low voltage and rapidly changes to a more positive voltage.
- Fig. 2C shows the resultant voltage waveform 4 that would occur on the sense side of the capacitor C. The voltage measured is proportional to: dV:,
- V t c * " ⁇ ⁇ ⁇ n
- C capacitance
- t time
- Vj n change in excitation voltage
- the pulse height is dependent on how quickly the excitation voltage (Vj n ) changes. Very fast rising voltages will produce a pulse height that is equal to the excitation voltage change, but never more.
- the amount of charge contained in a capacitor is related to the voltage present across it and its capacitance as:
- the amount of current present in the resultant pulse on the sense side of the capacitor C is equal to the change in the charge of the capacitor C caused by the change in the excitation voltage. Since the present invention uses an input amplifier with a large, yet finite, input resistance, the charge will be drained through that resistance. If there were no path for current to flow from the sensing side, the voltage would remain equal to the excitation voltage as the capacitor C has reached an electrostatic equilibrium. If a lower resistance to ground is placed on the sense side, the pulse will shorten in width, as this charge is given a lower resistance path to ground and the charge is drained more quickly. For a very fast
- this pulse shape will be equal to: v out v ⁇ n c
- R resistance to ground sensing side
- C capacitance
- Euler's number the base of a natural logarithm
- t time increment.
- This equation is the same as for discharging a capacitance, with good reason.
- the amount of charge 'stored' by a capacitor is the same as that absorbed from the excitation source and the same as that released in this indirect current.
- the capacitor does not actually store any net charge — it maintains a separation of charges.
- the current required to 'charge' the capacitor is actually transferred to its other side. In the process, a separation of charges is built up and maintained within the capacitor until the charges are allowed to recombine when the capacitor is discharged.
- Figs. 3 A, 3B and 3C are a representation of an admittance and its reaction to a rapidly changing voltage.
- Fig. 3A shows the excitation waveform 3 consisting of a negative voltage that is rapidly switched to a positive voltage.
- the indirect current passed through the parallel capacitor C p once again causes an immediate rise to the full excitation voltage.
- the current through the parallel resistance R p will maintain that voltage while also discharging the capacitor C p , and the sensed waveform 5 will be as seen in Fig. 3C. If a lower resistance to ground is added to the sense side, the indirect current through the capacitor C p will still cause an immediate rise to the full excitation voltage change.
- the voltage will then drop at a rate determined by the resistance to ground, to a level that is determined by the voltage division of the parallel resistance R p and that resistance to ground.
- Fig. 4B takes the admittance of Fig. 3B and adds a capacitance C ou t to ground on the sense side.
- a capacitance C out instead on the output provides a means for minimizing the voltage rise from the indirect current through the admittance capacitance C p . That charge is immediately 'shared' between the two capacitances C p and C out , reducing the immediate voltage rise sensed.
- the immediate voltage rise that will be seen is a result of the current division by the two capacitances C p and C ou t and is proportional to the ratio of the capacitances as:
- C p is more prominent in the term for the indirect current than for the charging current.
- C p affects the output voltage rise time more by shortening it through the indirect current passed through than by the lengthening of the rise time through discharging through the parallel resistance R p .
- the reason is that the indirect current is passed through immediately where the charge/discharge current is time-related. This reverses the expected effect of the admittance capacitance of C p — a larger value actually shortens the overall rise time of the circuit, governed by:
- the admittance circuit shown in Figs. 3B and 4B can also be used as a simplification of the general electrochemical schematic shown in Fig. 1.
- the circuit of Fig. 1 is regarded as an admittance of the series combination of resistances R_ e , R f and R se in parallel with the series combination of capacitances C ee , Cf and C se -
- the admittance values of Figs. 3B and 4B would be replaced by:
- the distances between the 'plates' of the capacitance's C ee and C se are on a molecular level, the distance from the electrode surface to that of the 'diffuse' layer and/or the Helmholtz layers, and measured in Angstroms or nanometers.
- the electrodes themselves will normally be separated by a range from micrometers to decimeters, the distance for the fluid capacitance C f . In this process the fluid capacitance Cf dominates, which helps to eliminate some of the electrochemical effects that affect the capacitances C ee and C se of the electrode interfaces A and B, such as their known variation with applied voltage.
- the only currents that pass through the admittance are those required to discharge the admittance capacitance C p and charge the output capacitance C out . This limits the amount of current drawn through the fluid thereby reducing the possibilities of chemical changes on the surfaces of the electrodes and in the fluid. These effects can be further reduced by using a bipolar excitation voltage and/or having the excitation voltage connected only when a measurement is made.
- the sensed voltage when using a high input resistance input amplifier, the sensed voltage will be near or equal to the input voltage when the cell is at equilibrium, so the sensed voltage will be as large as that input. This means that little or no signal conditioning or amplification will be needed. Adding a smaller resistance to ground at the input amplifier will decrease the sensed voltage and cause additional currents to constantly flow through the cell.
- the present invention measures the time it takes for the sensed voltage to reach a particular voltage or the voltage reached at a particular time. While any voltage level could be used for the former, using a level that is 0 volts for a bipolar excitation, or half the excitation voltage for an excitation that runs to and from ground, can make the design simpler and help reduce the effects of electrical noise. This time interval, or voltage, gives a single measurement of the complex effects described herein. Such measurements are well known and well suited for digital circuitry or conversion to analog signals.
- Fig. 5 and 6 represent data from a study on aircraft hydraulic oils. For cost reasons, these oils are never completely replaced in the aircraft systems. Instead, the guidelines given airline maintenance crews are to top off any loss of oil. The particular breakdown pattern of this oil creates an acidic content that can cause destructive corrosion of hydraulic system parts.
- the two graphs shown in Figs. 5 and 6 represent readings of fluid resistance and the present invention measurements made on a sample of new oil, well used oil, and a 50:50 mixture of the two, respectively.
- Fig. 5 is a set of resistance readings taken on the above- described samples over a variety of temperatures and shows the problems that can be encountered in using resistance (or conductance) measurements over a range of temperatures.
- the same simple two copper wire probe was used.
- a Hewlett Packard (HP) 5300 measuring system with an HP 5306A multimeter was used.
- HP Hewlett Packard
- temperature compensation for this method would be impossible, as the readings for the new oil cross over those of the other samples. Even if one knew the particular temperature a reading was taken at, the compensation could not be known as it would be impossible to separate the composition effects from the temperature effects.
- Fig. 6 shows the results using the present invention.
- a GW GFG8016G function generator was used as the excitation source and a Tektronix TDS 210 oscilloscope was used for measurements, with a xlO, lOMohm probe.
- the capacitance of this probe and the input circuitry of the oscilloscope itself was used as the input capacitor, C out - Fig. 6 shows that the composition and temperature effects can be clearly separated using this process. In this case, a simple temperature compensation would be required to allow accurate qualitative measurement of the oil over a wide temperature range.
- Fig. 7 shows the result of concentration measurements using the present invention on four different aqueous solutions. These results show that this process produces ionic sensitivity similar to typical conductivity measurements. In this case, these compositions make little change to the dielectric constant of the water but do change the fluid resistance which affects the charge/discharge of C out and C p . Measurements in the PPB range or less are clearly possible, with the sensitivity greatest for smaller concentrations. More importantly, Fig. 6 and Fig. 7 show the wide range of fluids that can tested using the present invention. By adjusting the probe design and sensing amplifier input capacitance, virtually any fluid or fluid bearing material can be qualitatively tested using this process.
- Figs. 8A-D, 9A-D and 10A-D show comparisons of the present invention, assembled as described for Fig. 6, and three common methods: conductivity, capacitance and intrinsic time constant.
- Figs. 8A-D show the results using the present invention in Fig. 8A, and the other three methods, Fig. 8B, showing resistance, or the reciprocal of conductivity, Fig. 8C, showing capacitance, and 8D, graphing the intrinsic time constant, all on distilled water over a range of temperatures from 80 to 200 degrees Fahrenheit.
- Figs. 9A-D show the results of using the four methods, respectively, on tap water over the same temperature range.
- Figs. 10A-D respectively compare the results for each method, with the result using distilled water being graphed against that for tap water.
- Figs. 10A-D these differences are further brought out by graphing the response to distilled water against that for tap water for each method.
- Fig. 10A representing the present invention, shows a very linear relationship between its temperature response for distilled water and tap water. This means that, while the measurements clearly show a sensitivity to the composition of these fluids, the present invention has an insensitivity to temperature related effects caused by compositional changes.
- Fig. 10B, IOC and 10D show that these three known methods have temperature responses that vary considerably according to fluid composition.
- Fig. 11 A shows a basic measurement setup according to the present invention.
- An excitation signal source 8 is connected directly to excitation electrode 9. Electrodes 9 and 10 are submersed in sample fluid 12.
- Sense electrode 10 is connected to input amplifier 11 with C out as the input capacitance. Any particular single measurement using the present invention gives a value that is a representation of the various electrochemical effects in the cell, primarily the resistances and capacitances of the fluid and electrode interfaces.
- Fig. 1 IB shows a representative waveform that would be measured by this circuit.
- Fig. 12A shows an alternate embodiment according to the present invention.
- a differential amplifier (11) is used to measure the voltage difference between the excitation (9) and sensing (10) electrodes. Subtracting the voltage on the sensing electrode (10) from that on the excitation electrode (9) gives a measure of the state of equilibrium of the cell. When at equilibrium, there will be a voltage close to zero as both electrodes are at virtually the same voltage. When the excitation voltage is switched to a new voltage level, this output voltage will immediately rise to the difference in voltage states and decay back to near zero volts as the cell comes to equilibrium to the new excitation voltage, as shown in Fig. 12B.
- This pulse output may also be measured for the time interval to a specific voltage level or the voltage at a specific time interval, either one, again, a measurement of the transient immitivity response.
- Fig. 13A shows another alternative embodiment according to the present invention, including the addition of a series resistance R s .
- excitation signal source 8 is connected through series resistance R s to excitation electrode 9.
- Electrodes 9 and 10 are submersed in sample fluid 12.
- Sense electrode 10 is connected to input amplifier 11 with C out as the input capacitance.
- Fig. 13B shows two representative waveforms generated by this embodiment, one from a low R s and one from a high R s .
- Fig. 13B shows two representative waveforms generated by this embodiment, one from a low R s and one from a high R s .
- Fig. 14 shows how using the measurements described in the preceding paragraph and shown in Fig. 13B can differentiate between qualitative changes due to solvent changes.
- samples of distilled water, ethanol, and a 50% mixture of the two have their rise times plotted against the series resistance Rs. Each has a clearly distinguishable slope. Essentially, the slope is proportional to the capacitances and thus the fluid's dielectric constant.
- Fig. 15 shows yet another embodiment of the invention similar to the circuit shown in Fig. 13 which included the addition of a series resistance.
- the use of an electronic component the resistance of which changes with temperature can effect a simple temperature compensation means.
- an element Rprc such as a thermistor, a resistance network including one or more thermistors, or a circuit capable of changing the resistance R s in response to temperature changes, in place of the series resistance, R s , and placing element Rpxc in thermal contact with the fluid
- a self-compensating probe may be constructed.
- element R P T C can change the transient immitivity response as the temperature changes in order to compensate for the change in temperature.
- the present invention can be very insensitive to compositional temperature dependencies, making a self-compensated probe as described useable over a wide range of temperatures and fluid compensations.
- Fig. 16A shows the addition of a series resistance on the excitation source.
- This embodiment allows the measurement of the current going into the cell, as opposed to the current that has passed through the cell to the input capacitance.
- the voltage sensing means is connected across the series resistance, R s .
- the voltage measured will be the current being drawn by the cell multiplied by the resistance of R s , and the output waveform is represented in Fig. 16B.
- the ultimate height of the voltage waveform can change along with the transient immitivity response as the maximum amount of current drawn will be primarily determined by the series resistance, R s , and the excitation electrode interface capacitance, C ee .
- This peak voltage change can be used to increase the sensitivity of the measurement under some conditions as well as provide a measurement primarily of the excitation electrode capacitance, C ee .
- Fig. 17A shows yet another alternate embodiment somewhat similar to that shown in Fig. 16.
- the voltage detection means is connected to the excitation electrode and circuit ground.
- the voltage detection means is connected to the excitation electrode and circuit ground. The voltage measured will be the result of the excitation voltage minus the voltage across R s caused by the current through R s as:
- V rt ou.,tt V i;n s R s
- Fig. 17B shows the waveform resulting from the circuit of Fig. 17A.
- the ultimate voltage achieved will essentially be Vi n , rather than a voltage determined by the current drawn through R s as in the circuit of Fig. 16 A.
- Fig. 18A shows another embodiment of the invention, wherein the voltage sensing means is connected to the excitation electrode 9 and the sensing electrode 10, as in Fig. 12 A.
- the series resistance R s is used between the excitation source 8 and the excitation electrode 9.
- Fig. 18B shows a representative waveform from this embodiment.
- this embodiment produces a voltage pulse that represents the state of equilibrium of the cell, but the ultimate voltage height of this pulse will be limited to the excitation voltage input minus the voltage drop across the series resistance R s , as a result of the current drawn through it.
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JP2003573409A JP2005519282A (en) | 2002-03-01 | 2002-11-18 | Measuring the presence and quality of fluids with transient imitation response |
CA002477594A CA2477594A1 (en) | 2002-03-01 | 2002-11-18 | Fluid presence and qualitative measurements by transient immitivity response |
US10/506,113 US20050149278A1 (en) | 2002-03-01 | 2002-11-18 | Fluid presence and qualitative measurements by transient immitivity response |
MXPA04008445A MXPA04008445A (en) | 2002-03-01 | 2002-11-18 | Fluid presence and qualitative measurements by transient immitivity response. |
EP02793954A EP1481239A1 (en) | 2002-03-01 | 2002-11-18 | Fluid presence and qualitative measurements by transient immitivity response |
AU2002359418A AU2002359418A1 (en) | 2002-03-01 | 2002-11-18 | Fluid presence and qualitative measurements by transient immitivity response |
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US7057393B2 (en) * | 2000-12-06 | 2006-06-06 | Massachusetts Institute Of Technology | System and method for measuring the dielectric strength of a fluid |
US6664793B1 (en) * | 2002-03-01 | 2003-12-16 | Allen R. Sampson | Fluid presence and qualitative measurements by transient immitivity response |
USRE49221E1 (en) | 2002-06-14 | 2022-09-27 | Parker Intangibles, Llc | Single-use manifolds for automated, aseptic handling of solutions in bioprocessing applications |
US20040193988A1 (en) * | 2003-03-26 | 2004-09-30 | James Saloio | Engine speed sensor with fault detection |
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- 2002-03-01 US US10/087,281 patent/US6664793B1/en not_active Expired - Fee Related
- 2002-11-18 MX MXPA04008445A patent/MXPA04008445A/en not_active Application Discontinuation
- 2002-11-18 JP JP2003573409A patent/JP2005519282A/en active Pending
- 2002-11-18 WO PCT/US2002/036921 patent/WO2003074998A1/en not_active Application Discontinuation
- 2002-11-18 CA CA002477594A patent/CA2477594A1/en not_active Abandoned
- 2002-11-18 EP EP02793954A patent/EP1481239A1/en not_active Withdrawn
- 2002-11-18 US US10/506,113 patent/US20050149278A1/en not_active Abandoned
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Also Published As
Publication number | Publication date |
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AU2002359418A1 (en) | 2003-09-16 |
US6664793B1 (en) | 2003-12-16 |
JP2005519282A (en) | 2005-06-30 |
MXPA04008445A (en) | 2005-09-20 |
US20050149278A1 (en) | 2005-07-07 |
CA2477594A1 (en) | 2003-09-12 |
EP1481239A1 (en) | 2004-12-01 |
CN1623087A (en) | 2005-06-01 |
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