Hello Joe,
Without knowing anything about your instruments, their operation or environment I'll throw-out some general things that I would investigate first: Inside your lab / building: * ESD control in your Lab - Check Mats - Straps etc. * Any cell or 2-way communication (maintenance personnel etc) If yes, then experiment. * Any heavy switching inductive loads e.g.. motors, HVAC.. capacitive- e.g.. fluorescent lighting systems. Other test equipment / computers. If Yes, then monitor the primary power source that feeds your instruments to detect / record any disturbance events they may be occurring. You mention that each instrument is on it's own "dedicated" line..It's possible that the timing of a powerline event could be critical in terms of operational function of your instrument. An event occurring at precisely the right (or wrong) time in relation to a vulnerable operation point for your instrument could affect only one out of the lot. * Cable routing & shielding - check to determine if any unshielded power or data cables running from your equipment are routed near any above mentioned machinery or cabling connected to that machinery etc. If you are using shielded wires on your equipment, verify proper termination of the shields at each source and destination point. Outside your lab: * Any transmitter towers in the immediate area ? If Yes, try to find out who owns it and inquire about it's usage e.g. frequencies, traffic (usage) relating to time of day etc. The FCC might be able to help ID the owner. * Any welding (e.g.. autobody shop) or construction nearby ? If Yes, find out their hours of operation. If you get a disturbance during that time, call and ask if they were just using their welding equipment. Monitor the power line that feeds your instruments to record day & time event(s) occurred. * Any intermittent mobile communication passing by your building, e.g.. Police, Fire, ambulance? I once read about an incident where a cash register at MacDonalds would go whacky every so often. At approximately the same time of day (but not everyday), one of the cash registers would ring up a few hundred burgers, a thousand orders of fries... etc.. The registers were replaced, but it didn't matter. The problem still existed. It took half a dozen consultants and thousands of dollars to determine the culprit. That culprit was a police transmitter. Apparently, this officer would occasionally have his lunch in the MacDonalds parking lot and use his 2-way radio to talk to his comrades. I'm sure there's dozens of stories like this, so don't dismiss a similar possibility. Good Luck, George > -----Original Message----- > From: marti...@pebio.com [SMTP:marti...@pebio.com] > Sent: Tuesday, September 07, 1999 5:04 PM > To: emc-p...@majordomo.ieee.org > Cc: marti...@pebio.com > Subject: Immunity Problems ?? > > > > > EMC Professionals, > > We have 42 of the same instruments installed in one laboratory. They are > each > installed on their own dedicated line. On a regular basis, an instrument > will > shut down during a run. The instrument that shuts down is different each > time. > > These instruments are laboratory equipment that meet Class A radiated > limits of > EN 55011 > and meet the immunity requirements of EN 50082-1. > > Any ideas as to the potential cause of the problem and possible ways to > resolve > the problem would be greatly appreciated. > > Regards > > Joe Martin > EMC/Product Safety Engineer > P.E. Biosystems > marti...@pebio.com > > > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > jim_bac...@monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators). > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
