Skin Conductance Sensing With Logarithmic Gain and Phasic Extraction
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Solution Overview
Problem
Existing skin conductance measurement devices struggle to separate emotional and thermal regulation components from skin conductance measurements, leading to inaccurate emotional state analysis due to interference from motion and temperature effects, and require high-resolution, costly components to cover the wide range of skin conductance values.
Innovation Solution
A sensor system with a logarithmic amplifier and digital processor that extracts phasic and tonic skin responses, using a logarithmic gain to optimize analog-to-digital conversion and reduce component complexity and cost, allowing for effective separation of emotional and thermal components over a wide range of skin conductance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution analog-to-digital converters are used to cover the full range of skin conductance values, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent segments the skin conductance measurement range into two distinct components: tonic skin conductance level (SCL) and phasic skin conductance response (SCR). By separating these components through signal processing, the system can use lower-resolution ADCs for SCL measurement while maintaining high precision for SCR detection, thus reducing overall device complexity while preserving measurement precision for emotional state analysis
Solution Approach 2:
The patent extracts the phasic SCR component from the total skin conductance signal using differential amplification and signal processing techniques. This extraction allows the system to focus measurement precision on the emotionally-relevant SCR component rather than requiring high precision across the entire conductance range, thereby reducing ADC resolution requirements and device complexity
2Ease of operation
If skin conductance measurement is performed at the wrist to enable wearable application, then ease of operation is improved, but measurement precision deteriorates due to motion and temperature interference
Solution Approach 1:
The patent employs dynamic signal processing techniques that adapt to motion artifacts and temperature variations in real-time. The system uses differential measurement approaches and signal filtering that dynamically adjust to changing environmental conditions, allowing accurate emotional state detection despite the motion and temperature interference inherent in wearable wrist-based measurements
Solution Approach 2:
The patent implements feedback mechanisms through differential amplification and signal processing that continuously monitor and compensate for motion and temperature effects. By comparing signals from multiple electrodes and using feedback loops to filter out common-mode interference, the system maintains measurement precision for emotional state detection while enabling comfortable wearable operation at the wrist
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient extraction of phasic and tonic skin responses, reducing the need for high-resolution converters and allowing for lower-cost, low-power implementations suitable for consumer products, while providing accurate emotional state analysis and cortisol response prediction.
Implementation Method 1
the amplifier has a logarithmic gain for generating an output signal which is a logarithm of the skin conductance
Implementation Method 2
an analog to digital converter for converting the analog output voltage to a digital output signal
Implementation Method 3
The skin conductance can be measured by placing electrodes on the skin, applying a voltage and measuring the current
Data Source
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AI summary
A sensor is for measuring skin conductance. An amplifier is used to convert the skin conductance into an analog output voltage which is then converted into the digital domain, so that the increase in tonic skin conductance and the phasic skin conductance response are obtained in the digital domain. The amplifier has a non-linear logarithmic gain, with a decreasing gain for increasing skin conductance values. The sensor enables detection of both increase in tonic and phasic signals and over a wide range of skin conductance. It provides optimal use of the analog to digital converter so that a lower resolution and therefore lower cost converter can be used.