Grace, It is possible that out-of-band emissions (lower than 150khz) can be causing a measurement error. I would think this is a possibility with a dimmer circuit. Try adding a 10 or 20dB attenuator in the measurement circuit, right at the signal output of the LISN (before any transient limiter). If you add 10dB, then you should see a 10dB drop on the analyzer. If it does not drop 10dB, then the out-of-band emissions are causing a problem. If you have a transient limiter, that can act as a comb generator if it is actually clamping periodic spikes from the EUT. I recently had an EUT that appeared to fail, but running the linearity check such as I described above showed that I had a problem. After replacing the transient limiter with a regular attenuator, and using an analyzer with a pre-selector instead of one without, I was able to get passing results. And always use as much attenuation in the analyzer as possible to prevent overloading the input. Bob R.
--- On Tue, 5/12/09, Grace Lin <[email protected]> wrote: Dear Members, Is there any specific instrument settings for taking power line conducted emission? It seems the dimming function of a dimmer brings up a lot of noise at low frequency such at 150 kHz. Disabling the dimming function brings down the emission up to 30 dB at 150 kHz in one case. Thank you. Best regards, Grace Lin - - 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.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. 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]>
