HI Brian, thanks for taking the time to do a round up... Much appreciated, and very interesting
Derek Walton L F Research ----- Original Message ----- From: "Kunde, Brian" <[email protected]> To: <[email protected]> Sent: Thursday, September 13, 2007 4:06 PM Subject: RE: Trouble with Chamber Lights - FINAL > Hello All. > > For those of you who have been following this thread, let me fill you in > on what we learned. Our most recent problem was caused by a single bulb, > second nearest our antenna. So we changed out all our bulbs with GE > MVR400/U bulbs and we are back in business. Thanks to Mr. Woodgate, two > bright individuals from GE Lighting contacted me and schooled me on > metal halide lights. > > As you may know, we were fighting intermittent noise from our metal > halide lights in our 10 meter chamber. We troubleshot the problem to a > single GE/Tungsram MH400/U/TU bulb. We speculated the problem was caused > by a failure in the bimetal switch and starter within the bulb. I have > been told by GE this is incorrect. > > Metal Halide lights function by generating a controlled continuous arc > within the arc tube between two electrodes. This arcing makes noise. > Period! Once the bulbs warm up the arc stabilizes and it generates less > RF noise. But for reasons beyond anyone's control, the arc can > intermittently go unstable for a few seconds causing increased noise > (ever see the lights change color). This problem can vary from bulb to > bulb and change during the bulbs life. Changing out the bulbs may help > for awhile but we have to consider this the nature of this lighting > technology. > > The chamber manufacturers mount these lights above the chamber in a box > (high-hat) lined with ferrite tile to minimize the RF noise from the > lights. Though this is a good approach and works well most of the time, > when the bulb arc goes unstable it can still interfer with your testing. > > > So, what do we do about it? > > 1. It helps to properly "burn in" new bulbs. Turn them on and let them > burn in for 100 hours, turning them off for only 1 hour per day. This > helps the arc to stabilize. > > 2. If you see noise from the lights during EMC testing, you will have to > test with the lights off. > > 3. If you can't handle the darkness, then you need to have a secondary > light source (stumble light) that will generate enough light to get you > by, such as incandescent or halogen. Keep in mind that both these light > technologies require more frequent bulb changes which can be a pain. > > Option 1: If you can't wait for standard Metal halide lights to recycle > back on, you may consider changing, at least a couple fixtures to Pulse > Start or Instant On lights which come back on a lot faster, even when > hot. These lights may introduce new noise problems but if you have > already decided to turn them off during testing then what does it > matter. > > Option 2: We found that the lights nearest the antenna are most likely > to cause noise that we can see while testing. So we are going to re-wire > our lights so we can turn off all but the two farthest from the antenna > (over our turntable). That way when we test we can turn off 6 of 8. If > we have trouble with these two, then we only have two lights to > troubleshoot instead of 8. > > I have a meeting with ETS-Lindgren in a couple weeks and the lighting > issue is on our agenda. If anything new comes from it I will pass it on. > > Good luck, > The Other Brian > > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of Kunde, > Brian > Sent: Monday, September 10, 2007 8:32 AM > To: [email protected] > Subject: RE: Trouble with Chamber Lights > > Does anyone have experience with "Pulse Start" Metal Halide lights? It > appears as if they took the unreliable starter electrode, bi-metal > switch and resistor out of the bulb and somehow use a high voltage pulse > from the ballast to start the bulb. One major advantage is the bulbs hot > re-start much faster (don't have to wait for the bulb to cool off before > the light will re-start). > > Anyway, we are speculating the problem with EMI noise from standard > metal halide lights are in the bulbs and more specifically, in the > unreliable bi-metal switch which falsely fires the starter electrode > causing EMI noise. Pulse Start bulbs seem to not have those parts so > maybe they are better. Or maybe they have there own problems. Any > information would be appreciated. > > The Other Brian. > > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of Kunde, > Brian > Sent: Friday, September 07, 2007 9:40 AM > To: Ray, Darryl P; [email protected] > Subject: RE: Trouble with Chamber Lights > > Here is an update on our progress. > > We are six days into our investigation and it appears the problem is > with the bulbs themselves. We thought we were using the GE MVR400 as > many has recommended (read below) but still having trouble with them. > The bulbs have a bi-metal switch inside which shorts out the sparker > (starter) once the bulb gets hot. We are speculating that this switch is > intermittent and will sometimes start up the sparker after the bulb has > heated up and this is the source of the emissions. Because this problem > is so intermittent, it makes it very hard to troubleshoot. After the > lights warm up it may take hours to see if the problem is still there or > not. > > We did the process of elimination method but we think we may have more > than one bulb causing the problem. So as we are changing out the bulbs > and plugging the lights back in, one at a time, we have to wait several > hours or more to see if we can continue to the next light. > > It is strange that after 11 years with no problems we all of a sudden > have nothing but trouble with these lights. We noticed the bulbs we > installed six months ago, though they came in a box that said "GE", the > bulbs say "TUNGSRAM" on the side. We found that Tungsram is a Hungarian > company that GE bought. I wonder if Tungsram is making these bulbs now > for GE and there is serious quality issues that is causing our problem. > The new bulbs we are installing do say "GE" on them but they look > identical to the Tungsram bulbs. > > Does anyone have good experience with other brands of metal halide bulbs > like Sylvania? I can't believe a stupid light bulb has my chamber shut > down for 6 days. > > Thanks to everyone for your replies. They have been most helpful. I keep > posting on this topic so hopefully the information will be helpful to > others someday. > > The Other Brian. > > > > -----Original Message----- > From: Ray, Darryl P [mailto:[email protected]] > Sent: Wednesday, September 05, 2007 7:24 PM > To: Powell, Doug; Kunde, Brian; Stone, Richard; [email protected] > Subject: RE: Trouble with Chamber Lights > > > Brian, > > I have been involved with many EMC labs in particular the design and > construction of semi anechoic chambers. This is trickily problem as > these lights are intended for warehouses not RF chambers. Metal Halide > lights are very efficient but can be noisy. > > I have had lots of trouble with intermittent noise spikes from the Metal > Halide lights. Based on what I have learned, the noise is probably > coming from the lamp itself and not the ballast. I have had had pretty > good luck with the GE MVR400 series (400 watt) of lamps. Make sure you > match the ANSI rating of the lamp to that of the ballast. This is > critical. > > The bulbs do lose their lighting output rather quickly, and should be > replaced about every 6 to 12 months. The lighting degradation is gradual > and may not be noticed if your using the chamber frequently. I have > made measurements over time on a given changer and the reduction is > indeed measurable. > > There always a chance of getting a noisy lamp so have extras on hand. > > Also the lights need to be on for at least 10 minutes otherwise they > will be spikee. > > Hope this helps. > > > Darryl Ray > > > Darryl P. Ray > > Principal EMC Engineer > Covidien - Respiratory Division > 5823 Newton Drive > Suite 110 > Carlsbad, CA 92008 > > Voice: 760-603-5882 > Fax: 760-603-5369 > email: [email protected] > Please note new company name (formerly Tyco Healthcare) address, phone > number and email address > > > > > > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of Powell, > Doug > Sent: Friday, August 31, 2007 2:54 PM > To: Kunde, Brian; Stone, Richard; [email protected] > Subject: RE: Trouble with Chamber Lights > > Brian, > > We have been using tungsten for several years without noise problems. > However, the life of the bulbs is very short (2-3 months). To combat > this we purchase traffic signal bulbs. There are several features in > these bulbs for temperature extremes, rough handling, etc. From my > experience with these I think they will last about 2 years. > > The problem is that I cannot locate a flood light version of a traffic > signal bulb, so this only works for general lighting. > > > > Thanks, > > -doug > > Douglas E. Powell > Senior Compliance Engineer > Corporate Product Compliance > > Advanced Energy Industries, Inc. > Fort Collins, Colorado USA 80525 > > > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of Kunde, > Brian > Sent: Friday, August 31, 2007 9:17 AM > To: Stone, Richard; [email protected] > Subject: RE: Trouble with Chamber Lights > > I forgot to add that we are seeing these spikes with nothing in the > chamber (No EUT being tested) We have all other power going into the > chamber disconnected, so the mast, turntable, applicance, camera and > test power is all disconnected. We have evern disconnected all wiring > going in and out of the chamber except for the Coax that goes to the > receiver. > > The Other Brian > > > -----Original Message----- > From: Stone, Richard [mailto:[email protected]] > Sent: Friday, August 31, 2007 11:11 AM > To: Kunde, Brian > Subject: RE: Trouble with Chamber Lights > > hi Brian, > i find it hard to believe its the buld itself, the fixture and/or its > wiring could be recieving transient or radiated emi within the ground > plane from other equipment running locally. I dont recall the freq > spikes that were showing up. > I use standard 100wt flood lights in my chamber, the electrical to them > is not the same as the electrical wiring for the turntable motor... > i would check that as well, you can filter that to. but it means taking > off the heavy turntable and doign some maitnenance,but it did work for > me a while back. > good luck > Richard, > > -----Original Message----- > From: Kunde, Brian [mailto:[email protected]] > Sent: Friday, August 31, 2007 11:00 AM > To: Stone, Richard; [email protected] > Subject: RE: Trouble with Chamber Lights > > > We have confirmed that the problem goes away when the lights are off. > For instance, last night we ran our receiver in Max Hold with the lights > off and not a single spike (16 hours). There are two 100db line filters > on the power to the lights mounded on the highhat bulkhead. In one > experiment, we bypassed the line filter for two reasons; If something in > the filter was causing the spikes, then the problem should have gone > away. It didn't. Also, if the source of the spikes were outside the > chamber or on the power line feeding the filter/lights, then the spikes > should have increased in amplitude. They didn't. So we feel the problem > is within the chamber, which narrows it down to the lights themselves or > the wiring. > > Today we will continue to try and narrow the problem down to a single > fixture, but as some have suggested, the problem maybe an inherent > problem with the ballasts or the bulbs. So the problem may be with all > the lights. Any additional information on known good ballast or bulbs > would be helpful. Our electrician said that he installed GE bulbs, but > could also get Phillips bulbs if we thought that would make a > difference. > > If the problem continues to allude us, we could become desperate enough > to replace all eight fixtures with new ones. Any recommendations on that > front? Other than LED, is there a better choice than metal halide for > chamber illumination? > > Thanks again for everyone's help. > > The other Brian > (head still bleeding) > > > > -----Original Message----- > From: Stone, Richard [mailto:[email protected]] > Sent: Friday, August 31, 2007 9:40 AM > To: Hall, Ken; Kunde, Brian > Cc: Crumm, Al > Subject: RE: Trouble with Chamber Lights > > Have you confirmed this with the power shut off to the bulbs? Perhaps > its the circuit powering the bulbs instead. Also i have seen in my > chamber sporadic emi spikes due to bouncing of all the unused shielded > cables whos ends are sitting on the conductive turntable floor, and > bouncing up and down, that was unique, but its gone once i insulated > them from floor. > > Can anyone reccommend a feed thru filter where all the BNC, RJ45 > connectors can be plugged in one side and then filtered out the other. > This would be to stop ambients since the hole is 3 in diameter and 4 > inches in lenght. i am gettign about 10 ambients, 6 radio, 1 aircraft > and 2 local ambients. > my eut and support cables only fill about 30% of the hole. > > thnaks > richard, > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of Hall, > Ken > Sent: Friday, August 31, 2007 9:24 AM > To: Kunde, Brian; EMC PSTC > Cc: Crumm, Al > Subject: RE: Trouble with Chamber Lights > > Hello, > > We had/have similar prolems and, I think, finally figured out it was the > base to lamp connections arcing. > > Please le tme know it thishelps. > > Regards, > > Ken Hall > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of Kunde, > Brian > Sent: Friday, August 31, 2007 6:06 AM > To: EMC PSTC > Subject: Trouble with Chamber Lights > > We have a Lindgren FACT10 (used to be called a FACT5) 10 meter > semi-anechoic chamber built 11 years ago. Recently we have been seen > sporadic spike emissions that interferes with our peak scans. We have > narrowed the problem down to the chamber lights, which are 8 metal > halide 400 watt lamps. > > We have replaced all the bulbs and the ballast but the problem is still > there. We have replaced the line filters used on the light circuit; also > no change. > > It is a real difficult problem to troubleshoot because the emissions are > so sporadic. We started disconnecting the lights one by one. With fewer > lights the problem seems to diminished, but it is like all the light > generate this noise from time to time. > > Other than the startup noise from these metal halide lamps, I thought > they are suppose to be very quite and not generate such EMI noise. I was > hoping some of you chamber owners out there may have some insight into > our problem. We are running out of ideas here. > > Could we have obtained bad or cheep bulbs? Is there a manufacturer of > replacement bulbs that are better? Is there a newer light technology > that is better than the 11 year old metal halide lamps? > > Any and all suggestions are welcome and appreciated. We are stratching > our heads bloody trying to figure this out. > > Thank you all, > The Other Brian > > > LECO Corporation Notice: This communication may contain confidential > information intended for the named recipient(s) only. If you received > this by mistake, please destroy it and notify us of the error. Thank > you. > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. 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