Re: Green/Yellow Earthing Leads

2002-09-02 Thread John Woodgate

I read in !emc-pstc that Peter Merguerian pmerguer...@itl.co.il wrote
(in 2D1037012914D4118DB8204C4F4F50203DDA3E@ITLLTD01) about
'Green/Yellow Earthing Leads' on Mon, 2 Sep 2002:

BTW IEC 60 204 standard for electrical equipment for machinery states the
bicolour combination GREEN-AND-YELOW shall be such that on any 15mm length
one of the colours covers at least 30% and not more than 70% of the surface
of the conductor, tje other colour covering the remainder of the surface.

That is the specification that appears also in other IEC standards, and
in many other standards for cables as well.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

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Green/Yellow Earthing Leads

2002-09-02 Thread Peter Merguerian

Dear Group,

What is the percentage of color over a surface area for the insulated
green/yellow earthing conductor. Is it better to have more yellow than green
or more green than yellow. I know North Americans prefer more green than
yellow and Europeans like more yellow than green. Any historical reason? I
hope it has nothing to do with the Boston Tea Party! Can the group we come
up with some compromise?

BTW IEC 60 204 standard for electrical equipment for machinery states the
bicolour combination GREEN-AND-YELOW shall be such that on any 15mm length
one of the colours covers at least 30% and not more than 70% of the surface
of the conductor, tje other colour covering the remainder of the surface.


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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





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RE: Telephone headsets

2002-09-02 Thread Peter Merguerian

Chris,

In your subject and ending you specify telephone headsets; in the body of
your message you specify connection to audio amplifiers.

For telephone headsets: use EN 60 950 and the RTTE Directive. Note the limit
of 50 Vac/75 Vdc is not applicable under the RTTE Directive. There is really
not much to comply with under EN 60 950 except for the flammability fo
materials - the standard does not yet address acoustic requirements as in
the UL60950 requirements.

For audio/video equipment: use EN 60065 however, the LVD does not apply
because of the 50 Vac/75 Vdc cutofff as mentioned in your e-mail. In this
case, you may wish to consider complying with the EMC Directive and just
make a declaration based on engineering judgement.



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
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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: Chris K. Poore [mailto:chr...@percept.com]
Sent: Friday, August 30, 2002 4:02 PM
To: EMC-PSTC
Subject: Telephone headsets



We have some telephone headsets that we want to CE Mark, but are not sure
what safety standard to use.  Additionally, I don't see any category under
the CE Marking directive that would be entirely applicable.  The LVD seems
most logical, except that the input voltage to the headsets is well below
the 75DC, 50AC cutoff.  The headsets will connect to an OEM audio amplifier
that has been evaluated to the LVD, and seems to contain all the necessary
isolation (we are not even selling the amplifier). The primary reason for
wanting to CE Mark is because a competitor is doing it.

Is there a safety standard that we should use that is specific to these
telephone headsets for EU compliance?

Thanks,

Chris K. Poore
Staff Compliance Engineer
-
Percept Technology Labs, Inc.
4735 Walnut #E  Boulder, CO 80301
303-444-7480 ext. 113
303-444-1565 Fax
mailto:chr...@percept.com
http://www.percept.com


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Re: Designing for low power conducted and radiated immunity - Thanx

2002-09-02 Thread John Woodgate

I read in !emc-pstc that Chris Chileshe chris.chile...@ultronics.com
wrote (in 01c25266.1d499aa0.chris.chile...@ultronics.com) about
'Designing for low power conducted and radiated immunity - Thanx' on
Mon, 2 Sep 2002:

I believe the gist of your responses was that it is a bit of a tall
order to try and get a filter that will let 25kHz signals through
and reject RF at 150kHz. 

No problem if the 25 kHz signals were sine waves. It's the harmonics in
the digital/pulse signals that make it difficult. If you put in a filter
(with a reasonably good phase response) at, say, 30 kHz, and then
amplified and hard-clipped the 25 kHz signals, you might be OK.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

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RE: Designing for low power conducted and radiated immunity - Thanx

2002-09-02 Thread Chris Chileshe

Hi group, 

Thank you everyone for your great responses on the subject.

Sorry I couldn't acknowledge your postings earlier than this and
sorry I haven't acknowledged your postings individually. Had
to go away somewhere - at short notice. Only just returned.

I believe the gist of your responses was that it is a bit of a tall
order to try and get a filter that will let 25kHz signals through
and reject RF at 150kHz. 

To this end, I am thinking I may have to design a separate filter circuit 
for the output while keeping my original filter strategies on the DC lines.
Any fundamental flaws in this reasoning? 

Gert and others raise a few points I would like to comment/pursue/query
etc. Note that I have to assume screened cable is not an option initially
and further that the output it is a PWM square wave with a maximum 
fundamental frequency of 25kHz and not 25kbit.. 

 2/ It has not been proved that the sensor actually
degrades when exposed to the signals.

My fault. I didn't supply you with enough information. I have the 
analog version of the sensor. Before addition of the pi-filters it
was very susceptible. With only LC filtering, it was much better 
but still showed mild susceptibility during conducted immunity 
tests although the radiated immunity was vastly improved. With 
PI filters, it was immune over the full test spectrum 150k-1G.

3/ A CM coil may be applied with a asym signal if certain
conditions are met (esp.  grounding )

I have had bad experiences with trying to use CM chokes on
asym. lines, but you make a point about grounding, so maybe 
worth another look? 

 5/ standard EMI filters of the pi-type will probably
   do the job. I recommend using off the shelve parts available easily.

I have heard conflicting reports on these devices. I have heard from
certain 'well-informed' sources that the SMT PI-filters which one can 
get from the big manufacturers do not work quite as well as filters 
made from discrete SM devices. Any experiences worth sharing - 
anyone? Is it all about 'horses for courses' i.e. the right filters for the job.

 7/ The value of reasonable impedance does not need to be
that high 300- 500 Ohms is sufficient. Don't over do.

That is a good point. I work to a minimum of 300 Ohms - and where I  
have to squeeze every last bit of the spectrum into the useable range 
on a ferrite, will accept slightly lower (usually means using larger 
caps-to-case to maintain the impedance ratio).

Thank you again for the wonderful responses.

- Best regards

- Chris Chileshe
- Ultronics Ltd


-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Chris Chileshe
Sent: Thursday, August 22, 2002 11:31 AM
To: 'emc-pstc'
Subject: Designing for low power conducted and radiated immunity



Dear all,

On the evidence of the quality of responses I have seen on more difficult
queries, I think this should be fairly straightforward for all you RF
engineers
out there.

My product is a small 3-wire pressure sensor which sends out a digital bit
stream encryption of the pressure measured. It's current draw is around
30mA max. The bit stream is around 25kHz, 5V TTL. The 3-wires are
simply supply (5-10VDC), Output (5V logic) and Ground.

I am trying to make the product pass conducted RF immunity tests to
EN 61000-4-6 (150kHz - 80Mhz) at 10V and radiated immunity tests to
EN 61000-4-3 (80Mhz - 1Ghz) at 30V/m. There is an intrinsic safety limit
on the overall capacitance I can use in the product.

My general thoughts are to use a PI-filter on each of the 3 lines with
the vertical section of the filter being ceramic capacitors to the metal
case enclosure. A limit of about 10nF exists (for other reasons) on
these capacitors.

The horizontal section of the PI will be made up of a series connection
of a ferrite (for high frequency suppression) and an inductor for the lower
frequencies where the ferrite is transparent - in that order.

My problems (sorry .. challenges) are as follows:

1 - I need to let a bit stream through at 25kHz, but reject RF at 150kHz
 without a common mode choke (output is not differential). Is this a
 tall order?

2 - The inductors that give me a reasonable value of impedance at these
 sub 1Mhz frequencies tend to be largish and have Self Resonant Freqs.
 in the test spectrum albeit some of them (SRFs) are in the radiated
immunity
 band where I expect the ferrite to be in charge of attenuation. Is this
 likely to cause me problems?

3 - Can I find a single ferrite that will cover the entire RF test spectrum
of
 EN 61000-6-2 ( 150kHz - 1Ghz) or is it generally accepted that even the
 so called 'wideband' ferrites (SMT 0603/0805 max) are good down to
 about 5MHz but no lower?

Any relevant comments welcome.

Best regards

- Chris Chileshe
- Ultronics Ltd



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