Abstract: Systems and methods of monitoring electrodermal activity (EDA) in human subjects suitable for use in wearable electronic devices. An EDA monitoring system can include first and second dry electrodes, an alternating current (AC) excitation signal source, a trans-impedance amplifier, an analog-to-digital (A-to-D) converter, a discrete Fourier transform (DFT) processor, and a microprocessor. The AC excitation signal source can produce an AC excitation signal having a predetermined excitation frequency, such as about 100 or 120 Hertz (Hz). The analog-to-digital (A-to-D) converter can include a sample-and-hold circuit that operates at a predetermined sampling frequency, such as about four times (4×) the predetermined excitation frequency of 100 or 120 Hz. The DFT processor can generate complex frequency domain representations of digitized, sampled voltage level sequences provided by the A-to-D converter for use in obtaining measures of a user's skin impedance or skin conductance.

Abstract: Systems and methods of monitoring electrodermal activity (EDA) in human subjects suitable for use in wearable electronic devices. An EDA monitoring system can include first and second dry electrodes, an alternating current (AC) excitation signal source, a trans-impedance amplifier, an analog-to-digital (A-to-D) converter, a discrete Fourier transform (DFT) processor, and a microprocessor. The AC excitation signal source can produce an AC excitation signal having a predetermined excitation frequency, such as about 100 or 120 Hertz (Hz). The analog-to-digital (A-to-D) converter can include a sample-and-hold circuit that operates at a predetermined sampling frequency, such as about four times (4×) the predetermined excitation frequency of 100 or 120 Hz. The DFT processor can generate complex frequency domain representations of digitized, sampled voltage level sequences provided by the A-to-D converter for use in obtaining measures of a user's skin impedance or skin conductance.

Abstract: Accurately measuring bio-impedance is important for sensing properties of the body. Unfortunately, contact impedances can significantly degrade the accuracy of bio-impedance measurements. To address this issue, circuitry for implementing a four-wire impedance measurement can be configured to make multiple current measurements. The multiple current measurements set up a system of equations to allow the unknown bio-impedance and contact impedances to be derived. The result is an accurate bio-impedance measurement that is not negatively impacted by large contact impedances. Moreover, bad contacts with undesirably large impedances can be identified.

Abstract: Accurately measuring bio-impedance is important for sensing properties of the body. Unfortunately, contact impedances can significantly degrade the accuracy of bio-impedance measurements. To address this issue, circuitry for implementing a four-wire impedance measurement can be configured to make multiple current measurements. The multiple current measurements set up a system of equations to allow the unknown bio-impedance and contact impedances to be derived. The result is an accurate bio-impedance measurement that is not negatively impacted by large contact impedances. Moreover, bad contacts with undesirably large impedances can be identified.

Abstract: Various examples are directed to a measurement system for measuring an electrical property of skin comprising an excitation circuit, a receiver circuit, and a sequencer circuit. The excitation circuit may generate a periodic excitation signal that, when provided to the skin, generates a response signal in the skin indicative of the electrical property. The sequencer circuit may be configured to activate the excitation circuit to provide the excitation signal to the skin. While the excitation circuit is activated to provide the excitation signal to the skin, the sequencer circuit may activate the receiver circuit to execute a first sample cycle to generate a first plurality of samples of the response signal. A first value for the electrical property of the skin may be determined based at least in part on the first plurality of samples of the response signal.

Abstract: Accurately measuring bio-impedance is important for sensing properties of the body. Unfortunately, contact impedances can significantly degrade the accuracy of bio-impedance measurements. To address this issue, circuitry for implementing a four-wire impedance measurement can be configured to make multiple current measurements. The multiple current measurements set up a system of equations to allow the unknown bio-impedance and contact impedances to be derived. The result is an accurate bio-impedance measurement that is not negatively impacted by large contact impedances. Moreover, bad contacts with undesirably large impedances can be identified.

Abstract: Various examples are directed to a measurement system for measuring an electrical property of skin comprising an excitation circuit, a receiver circuit, and a sequencer circuit. The excitation circuit may generate a periodic excitation signal that, when provided to the skin, generates a response signal in the skin indicative of the electrical property. The sequencer circuit may be configured to activate the excitation circuit to provide the excitation signal to the skin. While the excitation circuit is activated to provide the excitation signal to the skin, the sequencer circuit may activate the receiver circuit to execute a first sample cycle to generate a first plurality of samples of the response signal. A first value for the electrical property of the skin may be determined based at least in part on the first plurality of samples of the response signal.

Abstract: Systems and methods of monitoring electrodermal activity (EDA) in human subjects suitable for use in wearable electronic devices. An EDA monitoring system can include first and second dry electrodes, an alternating current (AC) excitation signal source, a trans-impedance amplifier, an analog-to-digital (A-to-D) converter, a discrete Fourier transform (DFT) processor, and a microprocessor. The AC excitation signal source can produce an AC excitation signal having a predetermined excitation frequency, such as about 100 or 120 Hertz (Hz). The analog-to-digital (A-to-D) converter can include a sample-and-hold circuit that operates at a predetermined sampling frequency, such as about four times (4×) the predetermined excitation frequency of 100 or 120 Hz. The DFT processor can generate complex frequency domain representations of digitized, sampled voltage level sequences provided by the A-to-D converter for use in obtaining measures of a user's skin impedance or skin conductance.