Signal distribution for patient-electrode measurements
First Claim
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1. Apparatus for electrically connecting measurement apparatus to a biological subject, the apparatus including a signal delivery circuit including:
- a current buffer having;
a current buffer input for receiving a signal from a signal source; and
,a current buffer output for supplying a current to an electrode attached to the biological subject;
a voltage buffer having;
a voltage buffer input coupled to the current buffer output; and
,a voltage buffer output for providing a voltage signal indicative of a voltage at the electrode, to a sensor; and
a DC offset control circuit coupled between the voltage buffer output and the current buffer input.
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Abstract
Apparatus for electrically connecting measurement apparatus to a biological subject, the apparatus including a signal delivery circuit including a current buffer having a current buffer input for receiving a signal from a signal source and a current buffer output for supplying a current to an electrode attached to the biological subject, and a voltage buffer having a voltage buffer input coupled to the current buffer output and a voltage buffer output for providing a voltage signal indicative of a voltage at the electrode, to a sensor.
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Citations
24 Claims
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1. Apparatus for electrically connecting measurement apparatus to a biological subject, the apparatus including a signal delivery circuit including:
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a current buffer having; a current buffer input for receiving a signal from a signal source; and
,a current buffer output for supplying a current to an electrode attached to the biological subject; a voltage buffer having; a voltage buffer input coupled to the current buffer output; and
,a voltage buffer output for providing a voltage signal indicative of a voltage at the electrode, to a sensor; and a DC offset control circuit coupled between the voltage buffer output and the current buffer input. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A current multiplexing system comprising:
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a plurality of current multiplexers having at least one input and a plurality of outputs; a first and second alternating-current current source, each current source having a constant magnitude and frequency, wherein the second current source is complimentary to the first current source, and wherein each of the first and second current sources is coupled to an input of a current multiplexer; a plurality of current delivery circuits, each current delivery circuit having an input, a current output and a voltage output, wherein each current delivery circuit input is coupled to an output of a current multiplexer; a plurality of electrodes, each of the plurality of electrodes being coupled to a current output of one of the plurality of current delivery circuits; and at least one voltage multiplexer having a plurality of inputs and at least one output; wherein each current delivery circuit comprises; a current conveyor, having an input and an output, the current conveyor input being coupled to the current delivery circuit input and the current conveyor output being coupled to the current delivery circuit current output; and a first buffer having; a voltage buffer, having an input and an output, the voltage buffer input being coupled to the current delivery circuit current output and the voltage buffer output being coupled to the current delivery circuit voltage output; a DC offset control circuit including an integrator coupled between the voltage buffer output and the current conveyor input; and
,a negative impedance circuit coupled between the voltage buffer output and the current conveyor output, the negative impedance circuit comprising; a compensation impedance having a compensation impedance value, a first terminal and a second terminal, the first terminal coupled to the current conveyor output; and a compensation amplifier having a compensation amplifier input, a compensation amplifier output and a gain, the compensation amplifier input coupled to the voltage buffer output, the compensation amplifier output coupled to the second terminal of the compensation impedance to provide a compensation current to flow through the impedance, and the gain and the compensation impedance values are selected based on the parasitic impedance value so that the compensation current has a magnitude substantially equal to the leakage current magnitude.
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18. Apparatus for electrically connecting measurement apparatus to a biological subject, the apparatus including a signal delivery circuit including:
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a first buffer having; a first buffer input for receiving a signal from a signal source; and
,a first buffer output for supplying a drive signal to an electrode attached to the biological subject; a second buffer having; a second buffer input coupled to the first buffer output; and
,a second buffer output for providing a sensed signal indicative of a signal at the electrode, to a sensor; and
,a DC offset control circuit coupled between the second buffer output and the first buffer input. - View Dependent Claims (19, 20, 21, 22)
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23. Apparatus for use in performing impedance measurements on a subject, wherein the apparatus includes:
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a signal source for applying a signal to a subject; a sensor for sensing signals from the subject; a processing system for controlling the signal source and receiving signals from the sensor; and
,at least one signal delivery circuit, including; a first buffer having; a first buffer input for receiving a signal from a signal source; and
,a first buffer output for supplying a drive signal to an electrode attached to the biological subject; a second buffer having; a second buffer input coupled to the first buffer output; and
,a second buffer output for providing a sensed signal indicative of a signal at the electrode, to a sensor; and a DC offset control circuit coupled between the second buffer output and the first buffer input. - View Dependent Claims (24)
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Specification