James, We run primarily two different types of Radiated Immunity scans depending on the desires of our customer.
1. Unmodulated > frequency set > level from forward power > apply modulation > dwell time > unmodulate > next freq. 2. Setup Sig Gen with Modulation Turned On Always > Set frequency and level to Sig Gen from Cal Tables > Dwell time > next freq/level. I believe these are the two most common methods used with slight variations from lab to lab. We have never considered turning on and off the modulation if using the preset output levels for the signal generator as in method 2 above. The only reason we turn off the modulation in the first method is to better read the forward power from the bi-directional coupler when we are leveling. Power meters do not accurately read the CW level when modulation is turned on (varies from one probe type to another). If you do consider getting the equipment to level, get a good bi-directional coupler and a good fast dual channel power meter. That way you can read both forward and reverse power and you can calculate SWR and amp output in watts on the fly. That way if something is not working right, like a cable or connector going bad you can see the SWR going up. This has clued us into problems several times in the past before they could be seen through other indicators. Since we write our own test software, we are always tweaking our code to add features and flexibility in our testing methods; often driven by requests from our customers. I would love to collaborate with other EMC Test Engineers to work out the details of these test and calibration methods and share ideas to improve the techniques used. But, since many labs are in competition with one another I often find them to be pretty tight lipped about such things. They don't want to give away all their secretes. Have fun. The Other Brian From: [email protected] [mailto:[email protected]] On Behalf Of Pawson, James Sent: Tuesday, August 21, 2012 5:23 AM To: [email protected] Subject: RE: 61000-4-3: Rate of application of field Hi and thanks for all the insightful emails. The way we perform the test in-house is... unmodulated > frequency set > level set from cal (instant application, no ramp) > apply modulation > dwell time > unmodulated > next freq I think we are all agreed that different test methods can result in different EUT behaviour. It would also appear that there is no consensus for an agreed method of testing. My main line of enquiry was to clarify the test procedure. I have seen cases where applying the field suddenly results in a momentary disturbance to the EUT that disappears resulting in a stable operating EUT during the dwell time. A slow increase in the field does not result in this momentary disturbance. Lack of a directional coupler means that measuring the RF field in realtime is difficult in our case to see what is happening at the moment of applying the modulation and changing the level. I guess the dwell time starts as soon as a stable RF field has been established. I'm also going to investigate leaving the RF modulation on and redoing our test procedure to level set with the modulation on constantly to see what difference that makes. Many thanks James ________________________________ From: Pawson, James Sent: 20 August 2012 10:54 To: [email protected]<mailto:[email protected]> Subject: [PSES] 61000-4-3: Rate of application of field Hello, I can't find any clauses in 61000-4-3 (radiated RF immunity) that deal with the rate of application of the RF field. My understanding is that the test is generally performed by setting the unmodulated carrier to the level contained within the calibration file and then suddenly applying the modulation. Is there any precedent for, or problem with, gradually increasing the modulated carrier field strength up to the required level instead of a more sudden application? I imagine a system like a mobile radio would involve a suddenly applied burst of RF when the transmitter is "keyed". Many thanks James - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]<mailto:[email protected]>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]<mailto:[email protected]>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[email protected]>> ________________________________ 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. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
