A simple frequency response compensation method for current probe measurements of ESD currents

The transfer impedance of a current probe is typically not constant within the current probe's operational frequency range. As it is based on induction, it will suffer from reduced sensitivity at lower frequencies. Thus, a current probe cannot be used directly in a time domain measurement. The low frequency roll-off of a current probe can severely distort the actual waveform. A simple frequency response compensation method is proposed here to enable ESD current measurements with current probes. The method enables a current probe to be used for time domain measurements, such as when measuring ESD transient current and estimating the total transferred charge. If a probe's datasheet provides the transfer impedance for the probe, no additional measurements are needed. Advantages and disadvantages of directly using the measured complex transfer impedance, instead of approximating the transfer impedance by a circuit, is discussed in this paper.