Muriel,
I once had access to a file that described the history behind adoption of
the standard bandwidths and time constants. It was fascinating. However, I
neglected to make a copy, and have not seen it for years.
Peak detectors are pretty well self explanatory. Whatever the peak signal
is, it is retained for a time much longer than the repetition rate of any
amplitude variation present. Average detectors respond to merely the
average level of an incoming signal over time.
the one most folks get tripped up on is Quasi-peak. These detectors specify
time constants for charge and discharge of the detector filtering. The time
constants are selected by reference to what kinds of signals cause the most
noticeable interference. In determining this, as I recall, tests were made
by having people listen to radio and watch television as the level, PRF and
duty cycle of interfering signals were adjusted. Having a good idea which
caused the most noticeable effects, the CISPR 16 committee devised
combinations of filter bandwidths and detector response to preferentially
accentuate interference of a bothersome kind, while de-emphasizing less
bothersome interference.
Perhaps we have people reading this list who took part in the formulation
of CISPR 16. It is an interesting picture of the relationship between the
"real world" of human beings, and the minutiae of our profession.
Cortland
====================== Original Message Follows ====================
>> Date: 04-Dec-00 11:12:01 MsgID: 1077-7188 ToID: 72146,373
From: Muriel Bittencourt de Liz >INTERNET:mur...@grucad.ufsc.br
Subj: Detectors used in EMC testing
Chrg: $0.00 Imp: Norm Sens: Std Receipt: No Parts: 1
List-Post: emc-pstc@listserv.ieee.org
Date: Mon, 04 Dec 2000 17:08:35 -0200
From: Muriel Bittencourt de Liz <mur...@grucad.ufsc.br>
Organization: GRUCAD
Subject: Detectors used in EMC testing
Reply-To: Muriel Bittencourt de Liz <mur...@grucad.ufsc.br>
Hello Group,
I have a couple questions about detectors used in EMC testing, namely:
- We use Peak, Quasi-Peak and Average detectors. What is the reason for
using this three different detectors?
- What is the principle of operation of each one of the detectors?
- When I make a DC test (equipment with DC feeding through the LISN),
the three detectors are still needed? Why?
- The Quasi-Peak and the Average detectors can be viewed as "filters"
that reduce the EMI seen by the receiver?
Thanks in advance for the help.
Best Regards
Muriel
==
Muriel Bittencourt de Liz - EMC Engineer
Group of Conception and Analysis of Electromagnetic Devices
Federal University at Santa Catarina
Florianópolis, Santa Catarina
Brazil
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