Jim,
This is probably very difficult to do (even without throwing in the requirement to be inexpensive). As you probably know, conventional joint impedances use a 4-terminal Kelvin probe, but this is done at 10 kHz, or so. At 100’s of MHz, the parasitics will probably dominate the measurement making it worthless. One could try to use a network analyzer (ok, inexpensive has gone out the window) to measure S21 (insertion loss) between two points and deduce the magnitude of the impedance between them. The insertion loss may vary rapidly with frequency (resonances) and make the measurement difficult to interpret. Practically speaking, I would be surprised if you were able to make a meaningful measurement of chassis bond impedance at these frequencies. You could measure it conventionally at an audio frequency and extrapolate. Ignoring resonances, which are determined by the test setup, the real impedance won’t rise faster than 20dB/decade of frequency, maybe only 10 dB/decade. Jim __________________________ James L. Knighten, Ph.D. EMC Engineer Teradata Corporation 17095 Via Del Campo San Diego, CA 92127 858-485-2537 – phone 858-485-3788 – fax (unattended) ________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of Jim Hulbert Sent: Thursday, June 18, 2009 2:29 PM To: EMC-PSTC ([email protected]) Subject: Chassis Bond Impedance Measurement What is an easy (and inexpensive) means of measuring the high frequency chassis bond impedance between two modules of a system? I would like to get an impedance value at 500 MHz and 1 GHz. Thanks. Jim Hulbert Pitney Bowes - 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]> - 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]>
