Hi Allen. What kind of cable/wire are you using to connect your metal chassis and your circuit ground to earth?
If you're using a small diameter cable, try using some wide earthing braid instead (surface area is more important than actual metal volume because of the skin-effect at the kind of frequencies involved with ESD/Fast transients). Provided you have a really good **RF** ground connection (ie lots of surface area), contact discharge into chassis isn't usually a hassle from my experience. The key is usually just to ensure you have a really low impedance path from your chassis to earth that doesn't pass through (or too near sensitive parts of) your circuit board. If you still have problems with a good RF earth, my experience has taught me some simple experimentation to find the coupling path is usually quicker to produce results than messing about with risking the health of expensive oscilloscopes. For example, try either (1) moving the circuit board away from the chassis, or (2) inserting a grounded shield (faraday cage style - perhaps aluminium foil?) around the circuit board; while still maintaining the same single-point circuit-ground-to-chassis connection. Repeating the test then should give you some idea of whether the interference is due to the energy from the ESD radiating from the chassis though the circuit board to get to earth or not. Hope that's of some help. Best of luck. At 09:57 AM 31/03/99 -0800, you wrote: >Does anyone have a suggestion on how to troubleshoot ESD problems? > >Specifically, I am having a problem with contact discharge to a metal chassis. The first thing that comes to mind would be to check for ground bounce with an oscilloscope when the ESD gun is discharged. For example, I thought of grounding the oscilloscope probe to the ground plane and then probing the circuit ground (which is electrically connected to chassis ground at one point). However, I have been told the ESD gun will probably cause interference with the oscilloscope, e.g. energy coupled into the scope probe, etc. > >Any advice would be greatly appreciated. > > >Allen Tudor, Compliance Engineer >PairGain Technologies tel: (919)875-3382 >2431-153 Spring Forest Rd. fax: (919)876-1817 >Raleigh, NC 27615 email: [email protected] > > > >--------- >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). > > ------------------------------------------------------------------------- Please note: The views, opinions and information expressed and/or contained herein do not necessarily reflect the opinions or views of Foxboro, the organisation/s through which this communication was transmitted nor any other third party, unless explicitly stated so. Peter Poulos (Hardware Design Engineer) Foxboro Australia 42 McKechnie Drive, Eight Mile Plains, QLD, Australia 4113 Tel:+61 (07) 3340 2118 Fax: +61 (07) 3340 2100 E-mail:[email protected] --------- 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).
