Device for measurement of electrical impedance of organic and biological materials
First Claim
1. A device for depth-selective measurement of electrical impedance in a test portion of organic or biological materials comprising:
- a probe having a plurality of measuring electrodes and a control electrode located between at least two of the measuring electrodes, one of the measuring electrodes also forming a predetermined reference electrode;
voltage and impedance measuring means for applying electrical potential over the measuring electrodes and for measuring electrical impedance of the test portion between the measuring electrodes; and
an amplifier that has a high-impedance input that is electrically connected to the reference electrode, the reference electrode remaining substantially unloaded by the amplifier, the amplifier also having a low-impedance output that is electrically connected to the control electrode;
an electric control field being adapted to extend from the control electrode into the test portion; and
a dynamic electrical potential of the control electrode being maintained during impedance measuring of the test portion.
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Accused Products
Abstract
A device and method for noninvasive depth-selective detection and characterization of surface phenomena in organic and biological material such as tissues by surface measurement of the electrical impedance of the material. The device includes a probe with a plurality of measuring electrodes separated by a control electrode. Measuring equipment measures impedance in a desired frequency range. An adjustable amplifier maintains a chosen control signal derived from the potential of one of the measuring electrodes at the control electrode without loading the measuring electrode. Depth selectivity is achieved by controlling the extension of the electric field in the vicinity of the measuring electrodes by the control electrode actively driven with the same frequency as the measuring electrodes.
214 Citations
17 Claims
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1. A device for depth-selective measurement of electrical impedance in a test portion of organic or biological materials comprising:
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a probe having a plurality of measuring electrodes and a control electrode located between at least two of the measuring electrodes, one of the measuring electrodes also forming a predetermined reference electrode; voltage and impedance measuring means for applying electrical potential over the measuring electrodes and for measuring electrical impedance of the test portion between the measuring electrodes; and an amplifier that has a high-impedance input that is electrically connected to the reference electrode, the reference electrode remaining substantially unloaded by the amplifier, the amplifier also having a low-impedance output that is electrically connected to the control electrode; an electric control field being adapted to extend from the control electrode into the test portion; and a dynamic electrical potential of the control electrode being maintained during impedance measuring of the test portion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for depth-selective, non-invasive characterization of a test portion of organic and biological materials, comprising the following steps:
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A) applying to a test surface of the test portion a probe that includes a plurality of measuring electrodes and a control electrode located between at least two of the measuring electrodes, one of the measuring electrodes also forming a predetermined reference electrode; B) applying electrical voltage to the measuring electrodes; C) applying a variable voltage to the control electrode with a predetermined phase shift and non-zero amplitude gain relative to the electrical voltage of a predetermined one of the measuring electrodes; and D) measuring electrical impedance of the test portion between the measuring electrodes. - View Dependent Claims (15, 16, 17)
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Specification