Measurement of transient electric field at the occurrence of electrostatic discharge when a charged metallic sphere approaches a grounded object

Abstract

Electrostatic discharge (ESD) is one of the electromagnetic wave noise sources which affect the function of mechatronics equipment. Spark lengths, discharge currents and electric fields at the occurrence of ESD were measured when a charged object approached a grounded object. It was confirmed that the spark lengths tended to shorten when approach speeds of the charged object increased. It was also confirmed that peak discharge currents tended to increase and rise times of the discharge current tended to shorten when the spark lengths shortened. Time change rates of electric field tended to become faster and amplitude spectra of the electric field tended to increase when the spark lengths shortened. Maximum values of time change rate of the electric field at 138 mm away from the point where ESD occured correlated with the peak discharge current, maximum values of the time change rate of the discharge current, and maximum second order differential values of the discharge current; quasi electric field was dominant among components of the electric field measured in this experiment.