Muriel, The Quasi-Peak and Average detectors are specified in CISPR 16. (EN 55016) I don't have a copy, so I can't provide you with cold hard mathematical details of what resistance, capacitance, ... is used. But I can tell you how and why they are used.
The Quasi-Peak and Average detectors are used to model a human's response to interference. For instance, assume that I made a device with a high peak emission that only lasted 1millisecond and that emission only occurred once every second. (1Hz with 0.1% duty cycle) I could turn that device on and let it interfere with your radio or TV. You probably wouldn't even notice. The emissions would cause glitches that are so quick and so far apart that a human being's sense of hearing wouldn't even pick it up. If you were to run this signal through a quasi-peak or average detector, you would get a reading that is very low compared to the peak value. This represents the fact that this signal would cause a very low level of annoyance to a human listener. (However, if these emissions had a sufficient peak value, they could cause problems with nearby edge triggered digital circuits, but that's different problem.) If my device put out that same peak level for 50microseconds and repeated it every 100 microseconds (10KHz with 50% duty cycle). Your ears would notice the interference. Your sense of hearing would "smear" the interference into a constant "buzz". This would definitely annoy you. The quasi peak detector is designed to pick up these types of signals. In order to do this, the quasi-peak detector uses a "leaky averaging" (usually an resistor/capacitor combination) circuit with a quick charge/discharge characteristic. In this case, the quasi peak detector and the average detector would give a reading very close to the peak value. This represents the fact that this type of signal would cause a high level of annoyance to a human listener. If my device put out that same peak level lasting for 500 milliseconds out of every second. (1Hz, 50% duty cycle) Then, you would definitely hear and be bothered by the interference put out by my device. You would hear a 1/2 second tone or buzz every second. This interference is slow enough that the quasi-peak detector may not yield a high reading. (I'm not sure where exactly, the cutoff frequency is, those who have CISPR 16 may be able to help with this.) However, the average detector will yield a high reading thus truly representing that you would be annoyed by this interference. So, in short, the quasi-peak detector models the human ear response to high-frequency, high-duty cycle interference. The average detector models the human ear response to low frequency, high duty cycle interference. Hope this helps, Chris Maxwell, Design Engineer GN Nettest Optical Division 6 Rhoads Drive, Building 4 Utica, NY 13502 PH: 315-797-4449 FAX: 315-797-8024 EMAIL: [email protected] > -----Original Message----- > From: Muriel Bittencourt de Liz [SMTP:[email protected]] > Sent: Monday, December 04, 2000 2:09 PM > To: Lista de EMC da IEEE > Subject: Detectors used in EMC testing > > > 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 > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
