マイクロギャップの火花放電に伴う過渡電界の光電界プローブを用いた測定波形の検証

抄録

With the widespread use of wearable terminals, machine to machine (M2M) and internet of things (IoT) equipment, electrostatic discharge (ESD: Electrostatic Discharge) due to electrification of humans and objects can cause electromagnetic interference (EMI) inside these devices, which is called intra-EMC (Electromagnetic compatibility). This type of the EMI issue would be often derived from a steep transient electric near field generated by less than 1 kV spark discharges between micro-gaps. To clarify the characteristics of such electric near field, therefore, an optical electric field probe, which does not disturb any electromagnetic fields to be measured, has been used to measure the transient electric field caused by a micro-gap spark when charged metal spheres collide, while it is not fully understood whether or not the probe output precisely responds to the transient electric field in the vicinity of the discharge point. In this study, the measured waveforms of the above-mentioned electric field are verified by comparison with the electrostatic field theoretically derived from image charges and the transient electric field calculated from an image dipole charge model combining a spark resistance law. The result reveals that at a distance near the discharge point the optical field probe does not properly work due to the presence of the electrostatic field, whereas the transient electric field at a distance away from more than twice the diameter of metal spheres from the discharge point can be correctly measured because of sufficient attenuation of the electrostatic field component.