RE: ISN or Current probe method on telecommunication ports?

2001-04-24 Thread Fleury, Bill 
Richard,
 
For shielded ports/cables the method used should be the current clamp method
as described in C.1.2 of Annex C, EN 55022:1998. The ISN is used for
unshielded ports/cables. We had the same problem of failing conducted
emissions when we used an ISN. When you put a current clamp on a shielded
cable you are seeing the data return currents on the shield. Connecting the
shield to earth through a 150 ohm resistor as specified in C.1.2 compensates
for that. At least that is my understanding; maybe others have more insight
into this.
 
Bill Fleury

-Original Message-
From: Richard Lee [mailto:r...@terawave.com]
Sent: Monday, April 23, 2001 12:31 PM
To: emc-p...@ieee.org
Subject: ISN or Current probe method on telecommunication ports?



Dear Colleague, 

Does anybody have done any conducted emission test on telecommunication
ports per EN55022 1998 standard requirement? 

Currently, we have performed a conducted emission test of our product on the
shielded telecom port by using ISN and current probe methods, and the
results of both tests are totally different.

With ISN method, the EUT failed the conducted emission on shielded telecom
port by 20 dB.  With current probe method, our product passed the conducted
test with good margin.

We don't know what is the theory behind the ISN and Current probe methods?
Can anybody explain to us or advise what we need to do to pass the conducted
emission test? Can the test lab accept the current probe method test data or
we have to meet both limits of voltage and current requirements that listed
in table 4 of CISPR. 22 1997 standard?

Our product used all shielded cables on telecom ports.  Per Clause 9.5.3.3 &
9.5.3.4 of CISPR. 22 1997, both methods are allowed for telecom port
testing.  

Any suggestions or feedback will be very appreciated.  

Thanks in advance! 

Richard Lee 
Compliance Engineer 
-- 
Terawave Communications, Inc. 
30680 Huntwood, Ave. 
Hayward, CA  94544 
Tel: 510-401-6590   Fax: 510-401-6628 
www.terawave.com

RE: ISN or Current probe method on telecommunication ports?

2001-04-24 Thread Praveen Rao 
Hi Richard,

I'm sure you are not the only one with doubts on this new standard for
Telecom port measurements.

I beleive that this standard is already under scrutiny and revisions are
underway to clarify some of the issues, especially for current measurement
methods.

About your question, I think you only need to comply with either the Current
limits or the Voltage limits of table 3 or 4 of EN55022:1998.

If you closely look at the bullet points under section C.1.2 :  Bullet 4
says "Voltage measurement is also possible ". I don't see any reason why
you need to comply with both Voltage and Current limits.

You mention about using ISN for your Voltage measurements.  ISNs are used to
measure the asymmetrical (common mode) emissions of unshielded symmetrical
(balanced) Telecom ports of the Equipmentg Under Test. In your case
(shielded ports) you may have to use a high impedence Voltage probe (not
defined in this standard, but similar to the one used in EN55014 but not the
same).  

This is my opinion and lets wait and see for the experts in this forum for
their comments.

Praveen Rao 

  -Original Message-
From: Richard Lee [mailto:r...@terawave.com]
Sent: Tuesday, 24 April 2001 3:31 AM
To: emc-p...@ieee.org
Subject: ISN or Current probe method on telecommunication ports?

Dear Colleague, 

Does anybody have done any conducted emission test on telecommunication
ports per EN55022 1998 standard requirement? 

Currently, we have performed a conducted emission test of our product on the
shielded telecom port by using ISN and current probe methods, and the
results of both tests are totally different.

With ISN method, the EUT failed the conducted emission on shielded telecom
port by 20 dB.  With current probe method, our product passed the conducted
test with good margin.

We don't know what is the theory behind the ISN and Current probe methods?
Can anybody explain to us or advise what we need to do to pass the conducted
emission test? Can the test lab accept the current probe method test data or
we have to meet both limits of voltage and current requirements that listed
in table 4 of CISPR. 22 1997 standard?

Our product used all shielded cables on telecom ports.  Per Clause 9.5.3.3 &
9.5.3.4 of CISPR. 22 1997, both methods are allowed for telecom port
testing.  

Any suggestions or feedback will be very appreciated.  

Thanks in advance! 

Richard Lee 
Compliance Engineer 
-- 
Terawave Communications, Inc. 
30680 Huntwood, Ave. 
Hayward, CA  94544 
Tel: 510-401-6590   Fax: 510-401-6628 
www.terawave.com