ESD guns, or electrostatic discharge guns, test the immunity of a device to electrostatic discharge. A vital piece of EMC equipment, ESD testing is necessary for a device to receive a CE mark (a symbol that denotes whether or not a product is allowed to be sold legally within the European Economic). The CE marking indicates safety and compliance, and that the device will not interfere with the use or function of other nearby electrical products. It also says that the marked device won’t cause shock and harm to a person that comes into contact with it – aka, the CE mark is a pretty big deal. In order to meet the requirements necessary for CE marking and create a safe product, a device must be put under three distinct test models for electrostatic discharge – human body, machine, and charged device.
The human body electrostatic test model creates the environment of a human body discharging static electricity. The device is then tested to see how it reacts to a person’s static electricity, and the resulting discharge is measured with an ESD gun. The most widely used application for this test in the United States is MIL-STD-883, which outlines the test parameters for the human-body model. In MIL-STD-883, the human body is emulated by a 100 pF capacitor and a 1500 ohm discharging resistance.
An ESD gun is used to monitor a DUT's (device under test) reaction when stimulated by static discharge from a nearby machine. Failure modes in machine model testing are similar to those in human body model testing. The test is applied in nearly the same way, except the resistance is 0 ohms and capacitance is set at 200 pF. While this test is not as frequently used as the human body model, it is still necessary to determine the electrical safety of a device.
The charged device model simulates situations that may happen in manufacturing environments. This test simulates a device charged either indirectly by electrostatic induction or directly by triboelectric effect. The charged device test model exposes the DUT to a charge at a standardized voltage level. If the device can withstand the voltage, the voltage is increased in increments until it fails, at which point the results are documented. CDM is standardized as ANSI/ESDA/JEDEC joint standard JS-002.
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Posted March 09, 2017