If you are going to make repeatable measurements two things have to hold true.
The LISN has to continue to provide its function, and the LISN has to be
close enough to the EUT that the mismatch between EUT, power cord and LISN
doesn't cause vswr errors. At 30 MHz, the power cord should be l/10, or one
meter. Of course that isn't the case, so there is already some question as to
the accuracy of the present measurement stopping at 30 MHz. It is pretty easy
to design a 50 uH LISN to 100 MHz, but you should check. Also, there are 5 uH
LISNs that have been designed to 400 MHz. Above about 2 MHz, it doesn't
matter whether you use a 5 or 50 uH LISN, so you have that possible
alternative.
If it were me, and I wanted to make accurate and repeatable CE measurements, I
would either shorten the power cord to one-tenth wavelength, or I would go to
a current probe measurement and slide the current probe up and down the power
cord looking for peaks (spectrum analyzer in max hold while scanning
frequencies and scanning the probe).
I also think it would be very important to discriminate between different
conduction modes, dm or cm or super-cm (current flowing same sense in phase,
neutral and safety ground).
From: "Garnier, David S (GE Healthcare)" <david.garn...@med.ge.com>
List-Post: emc-pstc@listserv.ieee.org
Date: Thu, 29 Sep 2005 10:55:58 -0500
To: <emc-p...@ieee.org>
Subject: Measuring Conducted Emissions above 30 Mhz
Hello EMC Guru's,
I am looking for some guidance...
Is there an established Standard & Test Method for measuring
AC Power Conducted Emissions above 30 MHz (say to 150 MHz?)
((Obviously, CE limits for CISPR11 only go to 30 Mhz.))
Thanks for your time,
Dave Garnier
David Garnier
e GE Health Care
___________________________________________
David S. Garnier
Senior Technician
Functional & CT Engineering
3000 N. Grandview Ave - M/S W-1250
Waukesha, Wi. 53188
Tel: 262.312.7246
Cel: 414.899.7580
- 2005 IEEE Symposium on Product Safety Engineering 3-4 October Schaumburg,
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