Mark: "Old" CMOS design may not have much protection. I would suggest that you play it conservatively. Unplug the cluster of input wires from your controller. Or, pull the boards from the backplane if you can. If this is somehow impossible, I would short the inputs to ground using wire braid or an impromptu woven wad of bronze wool.
Regards, Ed > -----Original Message----- > From: [email protected] [SMTP:[email protected]] > Sent: Tuesday, October 12, 1999 9:30 AM > To: [email protected] > Subject: EMI from nearby welding > > > The query I'd like to put to the readers of this list is not exactly > EMC related, but is close enough that I hope you'll forgive me > asking. > > Can anyone give me an idea of the voltages likely to be induced > in the unprotected input wiring of a process plant control system, > when welding is carried out nearby? Or point me to a resource > that may give me some help? > > The welding cables will be close (within a metre of the inputs to > the control system, perhaps even touching the control system > metal case). The welding transformer will be tens of metres > away. The process plant control system is an old logic design > based around 4000 series CMOS. > > The control system will not be energised when the welding is > going on, so my main worry is induced voltages/currents blowing > up the CMOS. Should I worry, or sleep happy? > > All advice gratefully received (except if someone tells me to throw > away the control system and get something better protected, as > that's not an option...) > > Regards, Mark > -- > Mark Hone > > Wellman CJB Limited Email: [email protected] > Airport Service Road Tel: +44 (0)2392 629239 (Direct) > Portsmouth, Hampshire Tel: +44 (0)2392 664911 > PO3 5PG, ENGLAND Fax: +44 (0)2392 697864 > > --------- > :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) Ed Price [email protected] Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 (Voice) 619-505-1502 (Fax) Military & Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) --------- 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).
