Overview
The indirect discharge part of ESD immunity test uses two planes, known as the vertical coupling plane (VCP) and the horizontal coupling plane (HCP) and coupled to the ground reference plane (GRP). The HCP remains in place under the EUT during the direct tests, the VCP to be placed at a 10 cm distance from the EUT. Each coupling plane requires a connected to the GRP by the GRC resistor lead, to ensure that any charge bleeds off within a few microseconds. The construction of these leads is critical: there should be a resistor close to each end, so that the length of lead between them is isolated from the connections and stray coupling to it is neutralized. Although power rating is unimportant, the resistors themselves should withstand a high pulse dv/dt without breaking down, for which low inductance carbon composition types are best suited.
