ElectroStatic Discharge

In 600 BC, Thales of Milet was the first one to "discover" electrostatic charging of objects. This makes this type of disturbance the oldest in its kind, but still responsible for many problems in present electronics. For this reason, the electrostatic discharge (ESD) test is a part of the measurements that have to be performed for obtaining the CE-mark.

There are different types of setups for the equipment under test (EUT), such as floor-standing and table-top equipment, but the latter is mostly used.

The tests are performed with a special generator connected to an ESD-gun. Through a predefined impedance, the pulse is carried to the EUT. The voltage of the pulse is between 2 kV and 15 kV and is dependent on the ambient conditions such as relative humidity, the material of the enclosure of the EUT and the type of discharge. The shape of the pulse from the generator is displayed at the bottom of this page. There are two types of discharge, namely contact and air discharge. Contact discharge is the preferred test method, so air discharge has only to be tested when contact discharge cannot be applied (e.g. anti-static material of EUT).
So performing direct and indirect application of discharges to the EUT is applicable in the following manner:

• Contact discharge to the conductive surfaces and to horizontal or vertical coupling planes;
• Air discharge at insulating surfaces.

When performing the tests it is required that the EUT and possible auxiliary equipment are exercising all normal modes of operation. The test results may be classified on the basis of the operating conditions and functional specifications of the EUT, according to the following performance criteria:

• (A) Normal performance within the specification limits;
• (B) Temporary degradation or loss of function or performance which is self-recoverable;
• (C) Temporary degradation or loss of function or performance which requires operator intervention or system reset;
• (D) Temporary degradation or loss of function or performance which is not recoverable, due to damage of equipment (components) or software, or loss of data.