Simultaneous impedance testing method and apparatus
Inventors
Xia, Yongshou • Kolasa, William • Garz, Eric
Assignees
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Publication Number
US-9594104-B2
Publication Date
2017-03-14
Expiration Date
Abstract
A method and apparatus for determining the impedance of the plurality of channels comprising a plurality of channels having a plurality of first channels and a plurality of second channels, at least one reference channel, a signal generator electrically connected to the plurality of channels, a reference signal generator connected to the reference channel, at least one amplifier connected to each of the plurality of channels and the reference channel and at least one filter connected to an output of the at least one amplifier to filter the output signal from the at least one amplifier. The signal generator is configured to provide a plurality of input signals to the plurality of channels. The reference signal generator provides an input signal to the reference channel.
Core Innovation
The invention relates to an impedance-testing apparatus and simultaneous impedance measurement method for a plurality of electrodes using a plurality of channels that include a plurality of first channels and a plurality of second channels. The apparatus includes at least one reference channel configured as a reference potential for the plurality of channels, a signal generator connected to the plurality of channels, and a reference signal generator connected to the reference channel. Signals are applied to the channel groups while a reference channel is driven for determining impedance based on filtered amplifier outputs.
A key aspect is the relationship among the input signals applied to the first channels, second channels, and reference channel, including opposite phase and phase relationships that minimize common mode voltage imposed on the amplifier of each channel and across the plurality of channels with respect to the reference channel. In some configurations, the second input signal is opposite in phase of the first input signal and is generated by means of an inverter connected in parallel with the output of the signal generator, and the reference channel input has a different frequency or an orthogonal phase shift with respect to the first and second input signals.
The invention includes amplification and a filter arrangement having a first filter and a second filter connected to an output of the amplifiers to filter the signals from the amplifiers. Impedance of the plurality of channels can be determined from the output signal obtained from the filter arrangement, including determining impedance of the first channels, second channels, and the reference channel by measuring the output from the at least one filter arrangement. The approach is directed to accurate impedance results and patient safety by avoiding excessive current through patient ground while increasing measurement speed for high electrode counts.
Claims Coverage
The independent claims cover an impedance-testing apparatus and several simultaneous impedance testing methods using multiple electrode channels with a reference channel, where selected input signal phase/frequency relationships minimize common mode voltage and impedance is determined from filtered amplifier outputs. The independent claims introduce inventive features in apparatus structure with opposite-phase/inverted inputs and filtering, and method steps that apply coordinated signals to channel groups and a reference channel and determine impedance using filtered outputs while minimizing common mode voltage.
Impedance-determining multi-channel apparatus with reference channel and opposite-phase inputs
An apparatus for determining impedance of a plurality of electrodes with a signal generator providing a first input signal to first channels and a second input signal opposite in phase to the first input signal generated by an inverter connected in parallel with the output, a reference signal generator providing an input to a reference channel configured as a reference potential, amplification with channel positive terminals and reference channel negative terminal connection, and a filter arrangement having a first filter and a second filter connected to outputs to determine impedance from the filtered output, wherein common mode voltage imposed on each channel amplifier is minimized.
Simultaneous impedance testing with different-frequency reference input and filtered output determination
A simultaneous impedance testing method providing an apparatus with first and second channel groups, at least one reference channel, a signal generator, a reference signal generator, amplifiers, and a filter arrangement; applying a first input signal to the first channels and simultaneously applying a second input signal opposite in phase to the second channels; simultaneously applying an input signal from the reference signal generator to the reference channel such that the frequency of the reference input signal is different from the frequency of the first and second input signals; measuring the output from the filter arrangement and determining impedance of the first channels, second channels, and the reference channel; wherein the input signals minimize common mode voltage across the plurality of channels and the reference channel.
Simultaneous impedance testing using orthogonal-phase reference input to minimize common mode voltage
A simultaneous impedance testing method determining impedance by applying a first input signal to the first channels and an inverse of the first input signal to the second channels; simultaneously determining the impedance of the reference channel by applying an input signal having an orthogonal phase shift with respect to the first and second input signals; and wherein the phase shift minimizes common mode voltage across the plurality of channels.
Impedance testing method minimizing common mode voltage using opposite-phase channel-group inputs and filtered measurements
An impedance testing method minimizing common mode voltage across a plurality of channels by providing an apparatus with first and second channels, at least one reference channel, signal generators, amplifiers, and a filter arrangement; applying an input signal to the reference channel; applying a first input signal to the first channels; simultaneously applying a second input signal to the second channels having the opposite phase of the first input signal; determining impedance of the reference channel by measuring the output from the filter arrangement connected to the reference channel; determining impedance of the plurality of first and second channels by measuring outputs from the filter arrangement connected therewith; wherein the input signals minimize common mode voltage across the plurality of channels and the reference channel.
Simultaneous impedance testing with minimized common mode voltage relative to reference-channel and different-frequency reference input
A simultaneous impedance testing method providing an apparatus with first and second channels, at least one reference channel, signal generator and reference signal generator, amplifiers, and a filter arrangement; simultaneously applying a plurality of input signals to the plurality of channels such that the common mode voltage of the plurality of channels with respect to the reference channel is minimized; simultaneously applying an input signal to the reference channel having a different frequency with respect to the plurality of input signals; determining impedance of the plurality of channels and the reference channel by measuring output from the filter arrangement; wherein the plurality of input signals minimize common mode voltage across the channels.
Simultaneous impedance testing method with reference input and opposite-phase, different-frequency second-channel input
An impedance testing method providing an apparatus with first and second channels, at least one reference channel, a signal generator, a reference signal generator, amplifiers, and a filter arrangement; applying an input signal from the reference signal generator to the reference channel; applying a first input signal to the first channels; simultaneously applying a second input signal to the second channels such that the second input signal has an opposite phase of the first input signal and the frequency of the second input signal is different from the frequency of the first input signal; measuring output from the filter arrangement and determining impedance of the reference channel; measuring output from the filter arrangement connected therewith and determining impedance of the first and second channels; wherein the input signals minimize common mode voltage across the plurality of channels and the reference channel.
Simultaneous impedance testing using switching arrangement to apply channel and reference inputs and measure filtered outputs
A simultaneous impedance testing method providing an apparatus for testing impedance of a plurality of electrodes comprising a plurality of channels having a plurality of first channels and a plurality of second channels, at least one reference channel, a signal generator connected to the plurality of channels and the reference by means of a switching arrangement, and amplifiers; applying a plurality of input signals to the plurality of channels by means of the switching arrangement; simultaneously measuring output from the amplifiers connected to the plurality of channels and determining impedance of the plurality of channels; applying an input signal to the reference channel by means of the switching arrangement; simultaneously measuring output from amplifiers connected to each of the plurality of channels and determining impedance of the reference channel; wherein the input signal, the first input signal and the second input signal minimize common mode voltage across the plurality of channels and the reference channel.
Across the independent claims, impedance is determined for multi-electrode channel groups and a reference channel using amplification and a filter arrangement, while the core inventive relationships among input signal phase and/or frequency, including opposite phase, inverse, orthogonal phase shift, and different frequencies, are selected to minimize common mode voltage. The apparatus and methods further coordinate applying channel-group inputs, optionally using an inverter or a switching arrangement, and measuring filtered outputs to determine impedance.
Stated Advantages
Minimizes common mode voltage, thereby reducing measurement error/noise.
Increases measurement speed for high electrode counts.
Supports accurate impedance results.
Improves patient safety by avoiding excessive current through patient ground.
Documented Applications
Biopotential measurements using ECG, EMG, EEG, and PSG, with impedance testing apparatus and simultaneous impedance measurement for multiple electrode channels.
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