Perhaps some of the confusion about this test procedure comes from recent transition from older (801) to newer editions of (1000-4) , generic and product family standards. (Yes, I'm somewhat oversimplifying this....)
With the old way (without the contact probe test using older 801 series with 1992 generic immunity) you need to hit all surfaces and vents areas with the rounded finger-size probe. If the air probe can enter the opening, you are obligated to test that opening with the air probe unless you provide clear ESD warnings (specifically the IEC symbols) near the opening, or at least include a caution in the user instructions. With the new way, having the contact probe officially ADDED to the existing test, then the rounded probe is primarily good for testing intended or accidental insulation defects, such as gaps or seams in plastic enclosures (like vents), molded cable hoods, and insulated but unshielded wiring. Otherwise the sharp contact probe helps make a reliable electrical contact with plated or decoratively painted surfaces for a more repeatable test where conductive parts can be or become (such as scratached paint) exposed. However, you can still do the ESD test both the old way with the air probe, AND follow with the contact probe. (As we normally do in our lab.) With rare exceptions, the only disadvantage is the extra few minutes required to complete the test. It simply gives you a bit more confidence in the product performance. Probably the most irksome issue with ESD is the way air discharge is performed by the test operator. I've seen many people, after getting explicit instructions on the proper technique, becoming hurried or fatigued (some ESD guns are heavy) such that they fail to charge the probe at a suitable distance (at least 10 cm) before approaching for a dischage. This risks producing different results and is the reason the contact probe is considered to be a more reliable and repeatable test method. Regards, Eric Lifsey Compliance Manager National Instruments --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
