To investigate electrostatic discharge (ESD) immunity testing for wearable electronic devices, the worst scenario i.e., an ESD event occurs when the body-mounted device approaches a grounded conductor is focused in this paper. Discharge currents caused by air discharges from a charged human through a hand-held metal bar or through a semi-sphere metal attached to the head, arm or waist in lieu of actual wearable devices are measured. As a result, it is found that at a human charge voltage of 1kV, the peak current from the semi-sphere metal is large in order of the attachment of the waist (15.4A), arm (12.8A) and head (12.2A), whereas the peak current (10.0A) from the hand-held metal bar is the smallest. It is also found that the discharge currents through the semi-sphere metals decrease to zero at around 50ns regardless of the attachment positions, although the current through the hand-held metal bar continues to flow at over 90ns. These discharge currents are further characterized by the discharge resistance, the charge storage capacitance and the discharge time constant newly derived from the waveform energy, which are validated from the body impedance measured through the hand-held and body-mounted metals. The above finding suggests that ESD immunity test methods for wearable devices require test specifications entirely different from the conventional ESD immunity testing.

There has recently been considerable interest in research on wearable non-grounded force display. However, there have been no developments for the communication of nonverbal information (ex. tennis and golf swing). We propose a small and lightweight wearable force display to present motion timing and direction. The display outputs a torque using rotational moment and mechanical brakes. We explain the principle of this device, and describe an actual measurement of the torque and torque sensitivity experiments.