Method and apparatus for continuous electrode impedance monitoring
First Claim
1. A method comprising:
- sending a test signal to a sensor of physiological data, said sensor having an impedance;
receiving a combined signal comprising a physiological signal component and a test signal component;
. filtering the combined signal to separate the physiological signal component from the test signal component; and
detecting changes in the impedance of the sensor by a comparison of test signal components.
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Accused Products
Abstract
In one embodiment, the present invention includes a test signal generator capable of producing an impedance test signal comprising of a sine wave having a known frequency. The test signal generator may include a crystal oscillator, a counter, and a lookup table. The lookup table output is applied to a digital to analog converter and is then low pass filtered using a conventional analog filter to produce a sine wave of a known frequency and voltage amplitude. The test signal flows through the electrode and combines with an electrophysiological signal to form a combined signal. A signal processor is used to isolate the combined signal into the test signal component and the electrophysiological component. The signal processor digitally low pass filters the combined signal and the output of the low pass filter is the electrophysiological signal. The signal processor then digitally bandpass filters the combined signal using a filter with a center frequency which is the same as the test frequency. The output of this filter is then used to calculate the electrode impedance.
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Citations
21 Claims
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1. A method comprising:
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sending a test signal to a sensor of physiological data, said sensor having an impedance;
receiving a combined signal comprising a physiological signal component and a test signal component;
.filtering the combined signal to separate the physiological signal component from the test signal component; and
detecting changes in the impedance of the sensor by a comparison of test signal components. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method comprising
communicating a test signal to a sensor of physiological data; -
combining a physiological signal with the test signal to create a combined signal; and
deriving both a physiological waveform and contact impedance from the combined signal. - View Dependent Claims (8, 9, 10, 11)
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12. An apparatus comprising;
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a test signal generator adapted to deliver a test signal to a sensor;
a signal processor adapted to receive a combined signal from the sensor and isolating the combined signal into a physiological component and a test signal component; and
a display adapted to display a physiological waveform derived from the physiological component and a contact impedance derived from the test signal component. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification