Wideband Measurement of Discharge Current Caused by Air Discharge Through Hand-Held Metal Piece from Charged Human Body

摘要

In IEC 61000-4-2 for electrostatic discharge (ESD) immunity testing, an ESD gun is used to simulate the ESD events from a charged human body. A gun of this kind injects into a device being tested the discharge current through a lumped resistor from a charged lumped capacitor. In actual ESD events from charged human bodies, however, the charge distributed on the body surface is discharged through a spark from the fingertip, and its situation is essentially different from that of the ESD gun. To understand the behavior of the above-mentioned discharge current, using a 6-GHz digital oscilloscope, we previously measured the current through a hand-held metal piece from a charged human body, and proposed an equivalent circuit model for calculating the discharge current with a time-invariant spark resistance. In this study, with respect to the approaching speed of the hand-held metal piece, we measured discharge currents through a metal piece from a human body with a charge voltage ranging from 200 V to 1000 V, and estimated the resultant voltage waveforms from the above-mentioned equivalent circuit model. Through these results, in conjunction with the metal piece speed, we demonstrated the dependence on the charge voltage of current peak, current rise time, time-varying spark resistance, spark length, and breakdown field. We confirmed also that the spark resistance value at the current peak time enables one to calculate the discharge current, which supports the validity of the previously proposed circuit model.