May I introduce you to EDA – our owl for electrodermal activity
This is EDA, our little owl with a special talent. EDA can measure electrodermal activity (EDA for short) – it detects the subtlest changes in skin conductivity precisely, reliably, and optimized for research and medical applications.
In this article, we explain the most important principles of EDA measurement, why the choice of measurement frequency is crucial, and how our system creates new possibilities in medical technology.
The shadowy shape of the owl on the sensor consists of two electrodes.
“EDA the Owl” was born during the development process from the idea of the sensor protecting its patients at night – because the sensor was originally designed for sleep monitoring and sleep research.
The sensor was developed as part of a funding project in close cooperation with the Clinic and Polyclinic for Dermatology and Allergology at Biederstein, Technical University of Munich, Department of Prof. Dr. Dr. Zink.
What is electrodermal activity? - Fundamentals for medical technology and research
EDA stands for electrodermal activity and is a fascinating phenomenon. The human body is a complex system, and just as an ECG can provide insights into heart function, EDA measurement provides insights into stress levels and the activation of the autonomic nervous system.
You can find more information about this in our previous blog articles, for example:
- Factors influencing EDA measurement
- Basics of electrodermal activity
- And in the literature, for example Christie Electrodermal activity in the 1980s: a review
Frequency response in EDA measurements - an underestimated factor
For the electrical engineers among us: The electrical parameters of EDA measurements are by no means trivial. There are no standardized measurement frequencies, and the choice of frequency has a significant impact on the measurement result. For historical reasons, other EDA sensors typically use DC or low-frequency AC measurements (< 100 Hz). This was because 100 years ago, when the first measurements were taken, this was the simplest option.
DC measurement (direct current)
- Advantages: Easy to implement, direct measurement of skin conductance.
- Disadvantages:
Electrode polarization can occur, leading to drift and measurement errors.
Long-term measurements are unreliable. - Typical application: Classical psychophysiological studies, e.g., lie detectors.
Low-frequency alternating current measurement (< 100 Hz)
- Advantages: Reduces electrode polarization compared to DC. Better suited for continuous measurements.
- Disadvantages: Can be affected by external interference (e.g. mains hum at 50/60 Hz).
- At low frequencies, e.g., 8 Hz, comparable results to DC measurements are obtained without their disadvantages.
Higher frequencies (> 100 Hz to approx. 1 kHz)
- Advantages: Even lower polarization effects. Better signal quality with short measurement intervals.
- Disadvantages: Penetration of the signal into deeper skin layers can lead to other physiological effects. Measurement can become more complex due to increased capacitive effects.
High-frequency measurement (e.g. 10 kHz)
- Advantages: Very low polarization. Enables impedance spectroscopy for analyzing different skin layers.
- Disadvantages: It no longer measures only skin conductance, but also capacitive and dielectric properties. Data interpretation becomes significantly more complex.
- Typical application: Research, e.g., to separate sweat gland activity from skin structure.
Our sensor allows for an adjustable frequency of DC to 30 kHz, ideal for research and comparative studies. For maximum comparability, we recommend 8 Hz, as this provides DC-like results but is more suitable for long-term measurements.
What makes our EDA sensor special
- Measuring range: 0.3 µS to 150 µS (or < 10 kΩ to approx. 3 MΩ)
- Measurement of real and imaginary parts of impedance
- Data storage over several days, readout via Bluetooth or USB
- Application in research: e.g., for the detection of allergic reactions – initial results are promising and are currently being published
→ More technical details can be found on our EDA sensor product page.
First scientific validation
Our sensor was used with great success in a scientific study conducted by Prof. Dr. Dr. Zink's research group at the Technical University of Munich. The team was impressed by both the sensor and the app's user-friendly design, high precision, and reliable data quality.
We are particularly proud of this first scientific validation.
Our EDA sensor is currently available as a functional sample.
If you are interested in integrating it into your medical technology applications, we would be happy to advise you individually on your requirements.
Please use our contact form or write to us directly – we look forward to speaking with you.