Electrodermal activity (EDA) is an important affective indicator, measured conventionally on the fingers with desktop sensing instruments. Recently, a new generation of wearable, battery-powered EDA devices came into being, encouraging the migration of EDA sensing to other body locations. To investigate the implications of such sensor/location shifts in psychophysiological studies we performed a validation experiment. In this experiment we used startle stimuli to instantaneously arouse the sympathetic system of n=23 subjects while sitting. Startle stimuli are standard but minimal stressors, and thus ideal for determining the sensor and location resolution limit. The experiment revealed that precise measurement of small EDA responses on the fingers and palm is feasible either with conventional or mobile EDA sensors. By contrast, precise measurement of small EDA responses on the sole is challenging, while on the wrist even detection of such responses is problematic for both EDA modalities. Given that affective wristbands have emerged as the dominant form of EDA sensing, researchers should beware of these limitations.

A torsion based shear mode energy harvester is used to power a wireless sensor module consisting of a microcontroller, a temperature sensor, an accelerometer and a wireless transmitter. A 10 cm3energy harvester was used and was found to produce nearly 450 μW of maximum power through an optimal load resistance under 0.5 gpkacceleration excitation at its resonant frequency. This harvester was then tested using a standard diode bridge rectifier which was assessed for its suitability in powering the wireless sensor module.