I read in !emc-pstc that John Cronin <[email protected]> wrote (in <[email protected]>) about 'Immunity testing of Headset', on Fri, 24 Aug 2001: > A technique commonly used and I believe may have been investigated > by British Telecom is to use a piece of plastic tubing (garden > hose) to couple the acoustic level to a point removed from the > field. Keeps the microphone out of the field and avoids perturbing > the field at the EUT. The system can be calibrated by holding an > acoustic calibrator against the EUT end of the tube.
With suitable precautions and a LOT of understanding of acoustics, this can work, but errors of 10 dB or more are easily caused and may go undetected. >We use a Bruel > and Kjaer microphone preamp and power supply (expensive kit). The > measuring device - psophometer/spectrum analyser must have a > bandwidth of less than 100 Hz at a frequency of 1 kHz. Where is that specified? A psophometer is a fairly broad-band instrument and there are several different standardized ones. If you use a spectrum analyser, what do you do with the results? > > Hope this is of use. I would welcome other comments on the > methods. BT did a lot of work and had a nice system that plotted > the telephone audible output against frequency, the older models > were not very good. There should be a paper available. What Bt's electroacoustics experts can do and what a test-house technician, however well-trained in antennas, CISPR receivers etc., can do are two potentially very different things! -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co..uk Eat mink and be dreary! ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
