Development of Immunity Test Method for Long-Duration Induced Noise on a Wearable Devices by Electrostatic Discharge

Abstract

In practical applications of wearable devices, there is a situation where the human body and devices are charged to high voltage, and their potential rapidly drops when electrostatic discharge (ESD) from the human body to a surrounding object occurs. In our previous study, we measured ESD stress induced on a portable oscilloscope held by a charged human when ESD occurs from the fingertip of the human to a surrounding object. We found that the duration of the induced noise on the wearable device is very long (ten to hundred microsecond order) when the input circuit of the wearable device exhibited high impedance. The noise could cause wearable devices malfunction due to its long duration. However, an immunity test on the long-duration noise is difficult because a charged human body is required for measuring the long-duration induced noise. In this study, we developed immunity test methods for long-duration induced noise. The methods do not require the human body. Method A uses an ESD gun and highvoltage relay and Method B uses a high-voltage DC power supply and high-voltage relay to simulate the charging of the human body and ESD from the charged human body. We confirmed that the proposed immunity test methods are effective.