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What is an Electrostatic Discharge Immunity Test
The primary goal is to replicate electric static and apply the event to a selected amount of test points. Common locations on todays commercial electronics include a USB port and the touch screen interface. Other locations on the chassis where a user may grab the product should be tested.
Quick ESD Testing Tutorial
Most engineers have fundamental EMC understanding, including the experience of witnessing the ESD testing in a test lab. The test lab often relies on the product manufacturer to determine the test points as they draft the test plan in accordance to the product compliance standard, IEC/EN 61000-4-2 is a common electrostatic discharge immunity test standard, often referred to in product standards.
Most ESD testing, to most standards, will instruct the technician to run a test sequence of ten discharges in one second intervals in both positive and negative polarity. The test standard may notate a ‘test environment’ consisting of a test bench and grounding plane. For pre compliance testing, this may not be necessary. But take care to not discharge near other (expensive) electronics in use. With each electrostatic discharge, an EM pulse is emitted from the simulator and can affect nearby equipment. For precompliance, ESD generators have a voltage potentiometer to identify failure thresholds.
Please watch the How-to-videos to learn about programming a test sequence into and ESD gun and watch the technique for air discharge.
ESD Contact vs Air Discharge
The goal is to directly apply the electrostatic discharge to the product under test using the contact tip. However, in most instances where a test point is to a non-conductive surface, the air tip is used. The user pulling the trigger to charge the air tip and approach until the discharge. There may be instances where an ESD event is not observed, assuming your electrostatic generator is functioning properly, this is OK and your product passes.
Other unique situations may require the air discharge test method, ie. the test point can’t be accessed by the contact tip.
How to Pass ESD Testing
Generating the criteria to determine hard and soft fails is often driven by the manufacturer of the DUT.