ESD monitoring circuit and device

摘要

An electrometer that is able to measure the potential difference of an electrostatically charged body without causing a rapid discharge of the subject charge. The electrometer has an input impedance that is in excess of 100 gigohms. The input impedance is created by an active voltage divider. The active voltage divider is a unique circuit which instead of the typical voltage divider that utilizes a passive resistive divider and an op amp in a voltage follower configuration, uses an amplifier configuration that attenuates its input signal. One result of this configuration is that the input line can then be guarded. This allows the device to be supplied with probes that are not subject to typical elements of degradation of the input signal with distance from the circuit, e.g. parasitic capacitance and bandwidth limitations. The device operates with two channels: a first channel recognizes the presence of a charged body in the proximity of the device, while the second channel measures the magnitude of the potential difference on a charged body examined by a probe. The device includes alarms that are activated when charge levels exceed a chosen level. A display tower allows a user to visually demonstrate to trainees the magnitude of ESC events.