Measurement of Active Sweat Glands
The skin is contacted by the first electrode which covers gland outlets. Inserted micro current (µI) finds its way through the sweat in the gland canals, through the epidermis, into the deeper levels of the skin which conduct extremely well (1,000 times greater conductance than the epidermis). The current then moves back out, through other active glands which are covered by the second electrode. The measured voltage (V) corresponds directly to the skin conductance.
The more sweat produced, the easier it is for the micro current to find its way and the higher the skin conductance. When a stressor occurs the sweat channels are filling up more and a peak in skin conductance appears. Then, when relaxation begins, no more sweat is produced and the sweat slowly dries out and is absorbed by the tissue.
That is why it is easier to drive up skin conductance level and why it takes longer to bring it down during the drying out period.
Major influences on skin conductance measurement
To measure skin conductance is not a trivial task. Various influences need to be considered and overcome to measure with the necessary precision.
- Contact area of the electrodes to the skin and Movement: Major influence. If the thumb tilts a bit and does not have full contact, the skin conductance changes in the ratio of the contact area which stays in contact compared to the full area. Solution: Overcome by the tilting lever and small control sensors next to the main sensor elements.
- Pressure of the skin onto the electrodes: Some influence, has short term (seconds) and long term (minutes) components. Mostly evened out through the necessary grip one needs to operate the mouse normally.
- Temperature of the surrounding: Some influence. In an office environment there is mostly even temperature through heating or air conditioning. Therefore respiration is mostly a reaction to the mental challenges.
The patented Logisens sensors are designed to overcome the above described influences. Based on 25 years of experience with miniaturized skin sensors, Logisens sensors measure with the necessary precision to give reliable feedback to create awareness and conduct trainings even during movements of the user. |
