Mr. Novak makes some excellent points. I was under the assumption that the
phrase voltage ripple implied conducted emission measurements at a LISN
port. Hence my comments on mode separation. Across a spectrum of even 30
MHz, any normal scope probe I know of (1 or 10 M Ohm in parallel with
So if I am worried whether the 1 us pulse width can be sustained, and I
don't know how to determine it analytically, my plan is as follows:
I put a wire probe in the room, run it to a spectrum analyzer tuned to the
transmit frequency, put the analyzer in zero span mode with a 1 or 3 MHz
Zero span can show rep rate or modulation but it cannot correlate the MHz
bandwidth waveform amplitude the scope sees with the amplitude of any
particular spectral component to which the spectrum analyzer is tuned.
Further, the spectrum analyzer is a much more sensitive device than the
scope, and
As I mentioned earlier, the waveform from a switching power supply has two
distinct components, due to the fast rise-time driving current into ground
(common mode) and the pulse itself which is differential mode. Separating
modes allows you to time window properly to really resolve the waveform
Charles,
Doing this kind of correlation is very difficult for the following reasons:
- unless you measure a very simple and dummy system, hardware today is
so complex that you cant predict for sure its activity; it is a strong
function
of time.
-tThe spectrum analyzer and scope will look at the
I read in !emc-pstc that Charles Grasso cgrassospri...@earthlink.net
wrote (in ekeeipjkkmpklafoobmcaelkcfaa.cgrassospri...@earthlink.net)
about 'Q on Correlation of Votage ripple with a Spectrum Analyser' on
Sat, 26 Jul 2003:
I first calibrated myslef using a known source - a sine wave.
Really?
I read in !emc-pstc that Charles Grasso cgrassospri...@earthlink.net
wrote (in ekeeipjkkmpklafoobmcoelhcfaa.cgrassospri...@earthlink.net)
about 'Q on Correlation of Votage ripple with a Spectrum Analyser' on
Sat, 26 Jul 2003:
Has anyone tried correlating the voltage ripple as seen on a scope
I read in !emc-pstc that Ken Javor ken.ja...@emccompliance.com wrote
(in bb48596e.36a1%ken.ja...@emccompliance.com) about 'pulse modulation
in reverb chambers' on Sat, 26 Jul 2003:
What is the limitation on minimum pulse width in reverberation chambers?
I expect it relates to room size, but
Ilan,
The date of cessation as given in the Official Journal of the European
Communities is not the last date for modifications but the last date on which
a statement of compliance to a particular version of a standard offers a
presumption of compliance with the safety objectives of the LVD (and
Sorry, but I don't understand the physics here. Could you please explain
how a 10 us delay could add 0.01 us to a 1 us pulse? A typical pulse rep
rate is 1 kHz. To me it seems that a 10 us delay would cause no
interference effect at all, since the first pulse is over and another isn't
due to
Charles,
Instead of using the 1GHz single-ended scope probe, have you tried to
connect the same coax cable that you made with the seriers 50 ohms for the
SA to connect to the scope? With a 50-ohm input impedance setting on the
scope, the loading of the planes would be exactly the same.
As I
Then the answer is the difference between the sum of all spectral components
measured with the scope vs. the individual components themselves. If you
want correlation you have to go the FFT route. From a strictly EMC
point-of-view only the spectral components matter, the only point of
That mostly makes sense, except I'm not sure about this part:
I'd expect a pulse to excite many modes within a chamber as long as either
its length or its transition times are shorter than the time it takes a wave
to travel across the chamber and back. That'll smear the pulse.
My thinking is
Ken,
A recent article on reverberant chambers mentions a Q of 83,000 or so. I'd
expect a pulse to excite many modes within a chamber as long as either its
length or its transition times are shorter than the time it takes a wave to
travel across the chamber and back. That'll smear the pulse. On
I read in !emc-pstc that Ken Javor ken.ja...@emccompliance.com wrote
(in bb4987fa.372a%ken.ja...@emccompliance.com) about 'pulse modulation
in reverb chambers' on Sun, 27 Jul 2003:
As long as
those delays are much shorter than 1 us (path difference much less than
300 meters), the original
I read in !emc-pstc that Ilan Cohen ico...@itl.co.il wrote (in
2D1037012914D4118DB8204C4F4F502045FE06@ITLLTD01) about 'Last day of
manufacture EN60950: A4, A11' on Sun, 27 Jul 2003:
Can anyone point me to the specified last day of manufacture for
products tested under EN60950: A4 and A11. (In
This is getting pretty intense for a Sunday!!
Both Mr. Javor and Mr Novak make excellent
observations. Both center on the method of measurment
as a point of concern.
To measure the voltage ripple I used a high
badwidth (1GHz) sigle ended probe with very
short leads. In order to establish the
You were correct in your initial interpretation. I am wondering if a 1 us
pulse can be established and not smeared over a longer period of time. The
source antenna emits a coherent wave with this pulse modulation envelope,
but many different rays taking different paths converge at the receive
I read in !emc-pstc that Ken Javor ken.ja...@emccompliance.com wrote
(in bb49768d.3717%ken.ja...@emccompliance.com) about 'pulse modulation
in reverb chambers' on Sun, 27 Jul 2003:
So if I am worried whether the 1 us pulse width can be sustained, and I
don't know how to determine it
Interesting observation. You said hum gets louder.
Implying hum is already there. What kind of phone?
Is it only that one telephone instrument?
Only occurs when LEDs are near the instrument, not near the
phone lines with the phone in another location?
Is the effect more pronounced at
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