|Publication number||US6865410 B2|
|Application number||US 09/920,679|
|Publication date||Mar 8, 2005|
|Filing date||Aug 1, 2001|
|Priority date||Aug 4, 2000|
|Also published as||US20020035339, US20040005024|
|Publication number||09920679, 920679, US 6865410 B2, US 6865410B2, US-B2-6865410, US6865410 B2, US6865410B2|
|Inventors||Robert Kavet, John C. Niple, Thomas P. Sullivan, Luciano E. Zaffanella|
|Original Assignee||Electric Power Research Institute, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (4), Classifications (7), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the benefit of Provisional Application No. 60/223,639, filed Aug. 4, 2000.
This invention relates generally to measuring and analyzing current flow through an animal or human body. More particularly, this invention relates to a portable contact meter analysis device.
For the purposes of this patent, contact current is defined as the current that flows in an animal or human subject when the subject touches (contacts) two different electrically conductive points in the subject's environment. Different conductive points with different voltage potentials cause current to flow in the living body.
Most current measurement systems use one of two basic methods. The first method is to insert a known impedance into the current path and measure the voltage across the known impedance. (Current, voltage, and impedance are all related by Ohm's law, which states that Voltage=Current×Impedance. With two known quantities, one can calculate the unknown quantity, current in this case.) The second method is to attach a coupling transformer around the current path and measure the current via the magnetic field generated from the current flow.
Both methods have significant disadvantages for a contact meter; and at present there are no devices available to measure this contact current. The first method requires that the current path be broken with a fixed impedance and that the fixed impedance not significantly alter the measured current. For contact current, the points of contact can be anywhere on the body. The current flow will generally occur throughout the volume of the body. Contact points can occur at more than two locations with different voltages at each point. Consequently, it is difficult to gather and process this information.
The second measurement method (using a transformer) also has a number of disadvantages. Current transformers of this type are usually insensitive and must be used with large primary currents (Amps). Contact currents are typically small, milliamps (mA) and microamps (uA), and need a sensitive measurement device. Sensitivity can be increased by increasing the size and weight of the transformer, but this makes the devices too cumbersome for human use. Thus, prior art devices have not successfully measured contact current.
An additional problem is that the transformer method measures the magnetic field created by the current. Environments with potential contact currents often have ambient magnetic fields. The transformer measures both the magnetic field from the current flow and the ambient magnetic field, and cannot differentiate the two sources.
Accordingly, it is desirable to provide an improved technique for measuring current flow in an animal or human body.
An apparatus for measuring contact current includes data acquisition circuitry with at least two sensor contacts to measure the voltage drop across an animal or human body. A portable data processing unit is connected to the data acquisition circuitry to process the voltage data to produce current flow data.
The invention provides a compact, lightweight, low-power device that can be used to flexibly and non-invasively determine the magnitude of current flowing through an animal or human body.
For a better understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:
Like reference numerals refer to corresponding parts throughout the drawings.
As indicated in
In general, an overall model of the body's impedance would have high impedance and high variability for the contact areas, skin, and extremities (fingers, hands, feet, toes, head, etc.); and low impedance and low variability for the torso, legs, and arms. In a preferred embodiment of the invention, the contacts 210 are placed on the legs, torso, or arms so that the voltage measured is across the arms, legs, and torso to reduce the impedance variability. Note that in
In a preferred embodiment of the invention, the output module 146 generates menus that are displayed on display 122. A user selects items on the menu or enters input through the data input interface circuitry 114 to control the behavior of the executable programs stored in memory 130. When so ordered by the user, the output module 146 preferably writes data to the removable memory 120 or to the display 122. In this way, the user can, for example, write current flow data 142 to the removable memory 120 and access that data on a different machine.
In a preferred embodiment of the invention, when the adjust threshold routine 134 is selected, the output module 146 prompts the user through the display 122 for a threshold value for a channel 230. The user may enter threshold values for one or all of the channels 230 through the data input interface circuitry 114. The adjust threshold routine 134 sets the adjustable threshold detector 308 to the threshold values input by the user.
Studies have measured impedances at various locations on the body and the ranges of values and averages for different sized individuals are available. The memory 130 preferably contains generic body impedance data 138 from such studies. Thus, generic body impedance data 138 contains estimated impedances for the living body 202. Preferably, this data includes data for bodies of different heights and weights.
When a user indicates through the data input interface circuitry 114 that the logging is to begin by pressing the appropriate key or sequence of keys, the data input interface circuitry applies a signal to the system bus 126 that the CPU 116 recognizes as an initiate logging command. The CPU 116 then executes the initiate logging routine 132. The initiate logging routine 132 starts logging voltages measured through the data acquisition circuitry 102 and conditioned by the acquired data conditioning circuitry 112. The voltages are stored as voltage data 144 in memory 130. The voltage data 144, as well as the current flow data 142 and accumulated body impedance data 140, could also be processed immediately, without storing to memory 130. In that case, the parameter calculator 136 would be run concurrently with the initiate logging routine 132, rather than subsequently, as discussed below for illustrative purposes.
Utilizing Ohm's Law, current=voltage/impedance, the voltage data 144, and the generic body impedance data 138, the parameter calculator 136 calculates current through an animal or human body 202. Voltage from the voltage data 144 and impedance from the generic body impedance data 138 are available. The results of the calculation are stored as current flow data 142. Note that “known impedances,” for the purposes of this calculation, are from the generic body impedance data 138 and are, in the strictest sense, estimates.
The parameter calculator 136 also utilizes Ohm's Law for the purpose of measuring impedance for the living body 202. The user sets current flow data 142 to a known value and runs a current with that known value through the living body 202. Preferably, additional contacts are used for this purpose. Voltage data 144 is accumulated as previously described. The parameter calculator 136 calculates impedance=voltage/current for the current represented in current flow data 142 and the voltage represented in voltage data 144. The calculated impedance is stored in accumulated body impedance data 140.
Utilizing Ohm's Law, current=voltage/impedance, the voltage data 144, and the accumulated body impedance data 140, the parameter calculator 136 calculates current through an animal or human body 202. Voltage from the voltage data 144 and impedance from the accumulated body impedance data 140 are available. The results of the calculation are stored as current flow data 142. Because impedance for each living body 202 is slightly different, calculating known impedances for an animal or human body 202 will generally result in more accurate current flow measurements than using the generic body impedance data 138.
Preferably, the data input interface circuitry 114 includes a button to stop the logging process initiated by the initiate logging routine 132. This button functions as a kill switch or cancel button.
The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the invention. In other instances, well known circuits and devices are shown in block diagram form in order to avoid unnecessary distraction from the underlying invention. Thus, the foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
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|U.S. Classification||600/407, 600/547, 324/692|
|International Classification||A61B5/053, A61B5/05|
|Nov 6, 2001||AS||Assignment|
Owner name: ELECTRIC POWER RESEARCH INSTITUTE, CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:KAVET, ROBERT;NIPLE, JOHN C.;SULLIVAN, THOMAS P.;AND OTHERS;REEL/FRAME:012354/0323;SIGNING DATES FROM 20011023 TO 20011101
|Aug 19, 2008||FPAY||Fee payment|
Year of fee payment: 4
|Oct 22, 2012||REMI||Maintenance fee reminder mailed|
|Mar 8, 2013||LAPS||Lapse for failure to pay maintenance fees|
|Apr 30, 2013||FP||Expired due to failure to pay maintenance fee|
Effective date: 20130308