ESD pulse waveforms (such as defined in the IEC 61000-4-2 standard) cannot be directly measured with any measurement instrument (oscilloscope) due to their high voltage and fast properties. 

The ESD target, the electrical and mechanical specifications are defined in the standard, is a kind of transducer from current to voltage by means of a low impedance with characterized frequency response over a specified range, allowing an appropriate scope to measure the voltage across the resistance (typically 2 ohm) of the ESD target.