I looked into this in detail quite about 18 years ago while I was working for HP. I had the quasi-peak adaptor that was used with the HP-8566 and HP-8568 spectrum analyzers. I dug through the schematics for the adaptor. There were two surprises.
The first surprise was when I read the standards document, it specified a critically damped response. My analysis showed two poles on the complex frequency plane, at 135 degrees and 225 degrees. My college controls book describes critically damped as the fastest response to a step input with no overshoot at the output. This puts two poles on top of each other at 180 degrees. A call to the spectrum analyzer division of HP in Santa Rosa brought me into contact with an engineer who told me that the definition of critically damped in Europe was (still is?) different than in the USA. The poles were where they needed to be by the European definition. The second surprise was a "mystery circuit" that didn't match any description in the standard. This "mystery circuit" took care of a discrepancy between the ideal response of a quasi-peak detector (which the preceding "critically damped" circuit would do) and the actual response of the analog meter used in the Rohde & Schwarz EMC receiver that was considered to be the standard at the time. I was told the difference was only a few tenths of a dB, depending on the nature of the signal. I don't know if the mystery circuit continues to be used. Don Borowski Schweitzer Engineering Labs Pullman, WA Ken Javor wrote on 08/23/2005 10:51:27 AM: > The quasi-peak detector is characterized by a charging time constant and a > discharge time constant. If I want to analytically determine the transfer > function of the detector for a given pulse duration and duty cycle, do I > only need consider the charging time constant? Is the discharge time just > there to enable a recording device (plotter pen) adequate time to respond? > > Thank you. > > Ken Javor > > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > Instructions: http://listserv.ieee.org/listserv/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: > > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc > This e-mail may contain SEL confidential or legally privileged information. The opinions expressed are not necessarily those of SEL. Any unauthorized disclosure, distribution or other use is prohibited. If you received this e-mail in error, please notify the sender, permanently delete it, and destroy any printed copies. This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/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: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
