EMC Regulations, standards and specs (particularly CISPR) relating to
commercial electronic equipment are aimed at controlling the pollution
electromagnetic spectrum and protecting radio communications against
radiated and conducted(MAINS PORT) spurious emissions . In particular,
CISPR 22 addresses the emissions limits at "Mains Port" in Table 1 and 2 of
clause 5.1.
Mains relates to a public utility supplying generally AC power, the
corruption of which would create a havoc particularly with AM reception,
possible Aircraft/.Airport comms and remote toys operating at 27 MHz.
Historically, in the civil sector, the parameters of the LISN were
determined by analysing the RF impedance of domestic, Industrial and other
"mains" supply systems. The mean values were found to be well represented by
an equivalent circuit of 50 ohm in parallel with 50uH.
Since good agreement was possible between several countries this LISN
network was adopted by CISPR in publication 16 as being suitable for AC
supply.
CISPR 14 treats DC ports as additional terminals, with the relaxed limits of
Table 1 and recommends the use of a HV Probe ("where a LISN cannot be
used"). So, the measurement and limits of DC Ports have been specified in a
CISPR publication, which could at least provide a guideline and be
consistent with the general CISPR philosophy.
You could always use a HV Probe with the tighter Class B limits, but at the
end of the day (and noting your commercial environment and not domestic)
economic realities would prevail and perhaps you would opt for the more
lenient "Additional terminals" limits of CISPR 14. We note that DC Port
measurements have not been mandated in any CISPR 22 publication.
In the interim period and if required by the client, I would tend to go this
way.
Regards
Arun Kaore
EMC Engineer
ADI Limited
Systems Group
Test & Evaluation Centre
Forrester Road, St Marys NSW 2760
P O Box: 315, St Marys NSW 1790
Tel: 61 2 9673 8375
Fax: 61 2 9673 8321
Email: kao...@sg.adi-limited.com.au <mailto:kao...@sg.adi-limited.com.au>
-----Original Message-----
From: VENTER, Francois [SMTP:fven...@alcatel.altech.co.za]
<mailto:[SMTP:fven...@alcatel.altech.co.za]>
Sent: Tuesday, 20 July, 1999 15:44
To: emc-p...@majordomo.ieee.org <mailto:emc-p...@majordomo.ieee.org>
Subject: CISPR 22 / EN 55022
Hi All
Due to local demand for the test, we have started to conduct conducted
emission tests on dc supply lines to the equipment. The reason why it is
demanded is that in a telecoms centre one does not have the equipment
connected to a dc battery. It is most of the time connected in parallel with
other equipment to a vast dc network. This test is of course not a
requirement in CISPR 22 or EN 55022.
My question relates to the limit lines in CISPR 22/EN 55022. Would you say
that it is valid to apply the limits in the standard to a conducted emission
test on a dc line. I currently use the same test procedure and LISN for both
ac and dc tests - Rhode & Schwarz (Receiver) & Scwarchbeck (LISN). I get
very repeatable results. Your comments would be appreciated.
Yours faithfully
FA Venter (PR. Eng.)
Alcatel Altech Telecoms
Senior Development Engineer - EMC
fven...@alcatel.altech.co.za <mailto:fven...@alcatel.altech.co.za>
PO Box 286, Boksburg, 1460, South Africa
Tel +2711 899-6658
Fax +2711 899-6590
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