Xing,
Section 5.2.3 of IEC 60950 (2nd edition) shows how this
measurement is made for Class II equipment. This should
be the same in China's GB 4943? standard.
See the paragraph near the end of 5.2.2 describing that
for Class II, accessible conductive parts or metal foil
wrapped around the unit are used to measure the current
to either phase or neutral. If your adapter is plastic
enclosed, with no exposed metal, the leakage should be
quite small.
You could also use the output pins as the "ground" side,
but these may not qualify as being exposed.
George
"xingwb" <xingwb%[email protected]> on 06/25/2002 05:56:33 AM
Please respond to "xingwb" <xingwb%[email protected]>
To: "Peter Merguerian" <pmerguerian%[email protected]>
cc: emc-pstc%[email protected] (bcc: George
Alspaugh/Lex/Lexmark)
Subject: Re: TOUCH CURRENT LIMIT
Hi Mr. Peter:
Our test lab receive a CB TEST REPORT FOR NATIONAL RECOGNIZATION,
the EUT is a class II ac adapter having a bridging capacitor (4700pF)across the
reinforced insulation
The touch current measured by CB is 0.17mA(4700pF declared)
but the value we measure is 0.28mA(4700pF)
which one is correct ?
it depend on test equipment?
How to judge
How to obtain accurate result?
any comments are appreciated
Xing weibing
2002-06-25 17:56
----- Original Message -----
From: Peter Merguerian
To: 'xingwb' ; Robert Johnson ; Peter Merguerian
Cc: [email protected]
Sent: Tuesday, June 25, 2002 6:38 PM
Subject: RE: TOUCH CURRENT LIMIT
Xing,
Yes, 0.25mA is very strict for 950. However, I can assure you that depeding on
the test lab and uncertainty of the test equipment, you will obtain slightly
different results.
This e-mail message may contain privileged or confidential information. If you
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PETER S. MERGUERIAN
Technical Director
I.T.L. (Product Testing) Ltd.
26 Hacharoshet St., POB 211
Or Yehuda 60251, Israel
Tel: + 972-(0)3-5339022 Fax: + 972-(0)3-5339019
Mobile: + 972-(0)54-838175
http://www.itl.co.il
http://www.i-spec.com
-----Original Message-----
From: xingwb [mailto:[email protected]]
Sent: Tuesday, June 25, 2002 11:13 AM
To: Robert Johnson; Peter Merguerian
Cc: [email protected]
Subject: Re: TOUCH CURRENT LIMIT
Dear SIRS:
Thanks for your e-mail
A further question for touch current:
Is it (0.25mA) strict for Class II equipment ?
0.28mA rms is OK FOR IEC60065
0.28mA rms is not OK for IEC60950
Any comments are appreciated
Best Regards
XING WEIBING
2002-06-25
----- Original Message -----
From: Peter Merguerian
To: 'xingwb' ; [email protected]
Cc: Ilan Cohen ; Michael G ; Shmuel Gnatt ; Sima Beloborodov ; Valery
Rodionov
Sent: Monday, June 24, 2002 9:00 PM
Subject: RE: TOUCH CURRENT LIMIT
Xing Hello!
ake a look at IEC 60990, "Methods of measurement of touch current and
protective conductor current". The limits in IEC 60 950 are based on this
particular standard.
Best Regards
This e-mail message may contain privileged or confidential information. If
you are not the intended recipient, you may not disclose, use, disseminate,
distribute, copy or rely upon this message or attachment in any way. If you
received this e-mail message in error, please return by forwarding the message
and its attachments to the sender.
PETER S. MERGUERIAN
Technical Director
I.T.L. (Product Testing) Ltd.
26 Hacharoshet St., POB 211
Or Yehuda 60251, Israel
Tel: + 972-(0)3-5339022 Fax: + 972-(0)3-5339019
Mobile: + 972-(0)54-838175
http://www.itl.co.il
http://www.i-spec.com
-----Original Message-----
From: xingwb [mailto:[email protected]]
Sent: Monday, June 24, 2002 1:57 AM
To: [email protected]
Cc: Rich Nute
Subject: TOUCH CURRENT LIMIT
Dear colleagues
I have a question regarding touch current limit of IEC 60950?
We can read from table 5A of IEC60950:1999:
Touch current limit for accessible parts and circuits not connected
to protective earth: 0.25 mA
question 1 : How does it (0.25mA) come from and what it is based on?
based on IEC479? OR other source
why it is not 0.5mA(based on IEC60479)
question 2 :for hand-held equipment it is 0.75mA
why ?
Please shed some light for above questions
Any comments are appreciated
Best Regards
Xing weibing
2002-06-24
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