Hi Jim,
A guideline I use for Criteria B is that the E.U.T may exhibit degradation
due to the field disturbance, but must self-recover after the field
disturbance is removed. What I have seen is that in certain power supplies
the secondary output voltage drops due to the surge, causing telco
PSNet
Ned is right, 3 layers of pre-preg are needed for separation of circuits
(hazardous to SELV, SELV to TNV, etc.) thru the board insulator to meet this
requirement under 950 - without Routine testing; Table 6A allows 2 layers of
prepreg but invokes Routine electric strength testing
I would use 6 dB as the correction factor for small EUTs. The 1 dB variance
was after taking into account the 6 dB difference identified with the
REFRAD.
As you had pointed out, the 1 dB left over is a function of luck, i.e.,,
the set up similarity between the EUT and the REFRAD and the
Don,
I would not use 1dB as the correction factor. You have not collected
sufficient statistics to consider this 1dB as systematic error, it is
rather within the accuracy of your measurements.
-Original Message-
From: umbdenst...@sensormatic.com [SMTP:umbdenst...@sensormatic.com]
Richard,
Up to 6 dB on a system with cables. 3 to 4 dB on floor standing equipment
and no cables. 2 - 3 dB on table top and no cables. Today we measured a
6ft telecom rank with one module and several cards and several cables. Some
cables went under the floor, some laid on the turntable, and
Is this online? - Mel
-Original Message-
From: wo...@sensormatic.com [mailto:wo...@sensormatic.com]
Sent: Wednesday, January 12, 2000 1:24 PM
To: emc-p...@majordomo.ieee.org
Subject: RE: transient suppression
World Products, a supplier of MOVs, has a very good, free presentation on
Jim,
I forget where I procured this definition for Criteria B but if you abide by
this definition, it would indicate to me that Due Diligence was exercised
when testing your apparatus. 10 minutes however seems to be a bit long,
where does this constraint come from?
the apparatus shall continue
Jim,
The situation you describe would be criterion C, because there is a
temporary loss of function and it is recoverable.
Scott Lacey
-Original Message-
From: Jim Hulbert [SMTP:hulbe...@pb.com]
Sent: Wednesday, January 12, 2000 3:08 PM
To: emc-p...@ieee.org
Subject: Surge
I echo Tony's words. I've just extended my chamber to 24' from 20', it makes a
huge difference. I have some channel section left over if you need it...
I replaced the flimsy roof section with 3 by 4 by 3/16 box section steel
too, just to help keep the roof straight...
Derek.
Tony J. O'Hara
Here is the URL for the regulation that takes effect 1 Feb. 2000. There is
also an explanatory document. Both are in German. French and Italian will
soon be available.
The regulation: http://www.admin.ch/buwal/recht/d/vo/davonisv.pdf
I see I omitted an important phrase in my previous response -- EUT emission.
I tested a small EUT in the chamber and found the correlation to be off by
as much as 7 dB when measured again at the OATS. When I compared the REFRAD
data of the OATS to the REFRAD data of the chamber, I found a 6
A product has a switched mode power supply with a current sensing circuit that
causes the supply to shut down when a surge pulse is applied to the AC mains in
accordance with EN61000-4-5/IEC1000-4-5. After about 10 minutes, the supply can
be turned back on and normal operation of the product
Jeff Chambers wrote:
There is also the 'hybrid' transient suppressor, an assembly consisting of a
gas discharge tube, followed by a series resistor (or inductor), followed by
a suppression diode...
Yes, a comprehensive protection approach is likely going to include
combinations of MOVs,
Mike Hopkins wrote:
Keep in mind rise time (really - turn on time) doesn't mean much on the AC
mains. Most specs assume the measurement is made right at the body of the
device, so even short wires will add enough inductance for a fast wave to
make the arguement moot.
Mike,
That's a
World Products, a supplier of MOVs, has a very good, free presentation on
the application of all types of protection devices. I highly recommend the
presentation.
Richard Woods
--
From: Ken Javor [SMTP:ken.ja...@emccompliance.com]
Sent: Tuesday, January 11,
David,
You might still have fighting chance to generate satisfactory field
uniformity in the semianechoic room over the area appropriate to the size of
your product. For products smaller than 5ft x 5ft, you can use lesser number
of points to determine field uniformity. If you do so, you can
Gary, what correlation error in dB did you think you had?
Richard Woods
--
From: Gary McInturff [SMTP:gmcintu...@telect.com]
Sent: Wednesday, January 12, 2000 12:26 PM
To: Barry Ma; mmate...@foxboro.com
Cc: emc-p...@majordomo.ieee.org
Richard,
It was correlation between two OATS' at opposite sides of Atlantic.
Correlation
for a desktop PC size product with cables and peripherals was within couple
dB.
Correlation factors needed frequent updates and program was soon abolished.
Mirko Matejic
-
This message is
Is it possible that the correction factors you got from RefRad* cannot give the
same good results when measuring real EUT? In other words, different EUT would
probably need different correction factors. I'm just curious.
*RefRad is a comb generator produced by EMCo - a part of ETS now.
Barry
Don,
We have made correlation between our chamber and OATS using the CNE meter at
several positions in the uniform field of the chamber. Chamber antenna
fixed, Oats antenna scanned. We have created a correction table whereby one
point or an average of several points can be used depending on the
REFRAD -- Reference Radiator, a comb generator that puts out pulses at 10
kHz or 1 MHz or 5 MHz spacing.
EMC Test Systems sells it under the model number REFRAD Model 4630B. The
pulse amplitude is not specified, but the output is amplitude and frequency
stable. Battery operated, can
Yes, the coil inductance would reduce the antenna length. Also it would change
the antenna impedance. To accommodate all related factors people usually use
ferrite bar with two windings - the primary to the monopole antenna, and the
secondary to an amplifier.
Barry Ma
Anrutsu Comany
Barry,
I'm guessing that part of the reason are the complex geometries that
can be generated in rooms with reflections etc - even using the abosrbers.
So small changes in equipment arrangement can throw things way off. Meaning
that you can't rely on the repeatibility of the correction
Hi David
In my experience that is just a little too short. The smallest chamber I'm
familiar with that would satisfy 61000-4-3 (80MHz -1GHz) is 7L x 3.4W x 3 H
meters. This size is usually called a compact anechoic chamber. It can
also be effectively used for pre-compliance of emissions testing!
If you have not already done so, I would suggest posting your
question on the emc-pstc listserver, where there are many more
qualified people.
Form my power supply days (years ago) here are some thoughts:
1. If your load is resistive, e.g. a hair dryer, it will make
little diffewrence.
2.
Mirko, what level of correlation error (in dB) did you achieve between the
chamber and OATS.
Richard Woods
--
From: Matejic, Mirko [SMTP:mmate...@foxboro.com]
Sent: Wednesday, January 12, 2000 9:59 AM
To: emc-p...@majordomo.ieee.org
Subject:
Keep in mind rise time (really - turn on time) doesn't mean much on the AC
mains. Most specs assume the measurement is made right at the body of the
device, so even short wires will add enough inductance for a fast wave to
make the arguement moot.
-Original Message-
From: Dan Kwok
Clamps are necessary if you don't want the AC mains shorted to ground for
each transient event.
MOV's are the most commonly used suppressors for the AC line. Use MOV's
rated at higher than the peak AC voltage expected on the mains. Clamping
voltages are typically in the 300 to 500V region;
In my notes from university (when cps was prevalent) I see that originally
kcps was written and even mcps (handwriting was terrible hard to tell
whether the m was capital or not, the m for millivolts was always written
mV), then when the change to Hertz came about (that probably should be
hertz)
David:
I would be very cautious about personal cell phones field intensity
measurements . The proximity of the antenna is so close to the body (head)
that some field intensity values I've heard about approach 200-500 V/.m.
The power from such devices is very low but close proximity puts it in
Is it feasable to convert a 5 x 4 x 3 meter unlined shielded room to meet field
uniformity requirements of 61000-4-3 using absorbing tile or wedges? Ballpark
estimate?
Thanks,
David.
David Gelfand
Memotec Communications Inc.
Montreal Canada
-
This message is coming from the
Barry,
Request was to measure radiated emission levels in compact semianechoic room
and predict measured levels at a specific OATS. In order to achieve this
goal I proposed to adjust room antenna factors, or to introduce correlation
correction factors for measurements in a room. Measurements in a
Barry,
Thank you for your comment. What we are trying to do is establish better
correlation between the chamber and OATS so we minimize our time in the
heat, humidity, rain and bugs (South Florida) at the OATS. We are not
trying to replace the OATS with the chamber.
We have recently been
A good hit on Firewire can be got at http://www.whatis.com (enter
firewireas the search string)
-Original Message-
From: david_inst...@uk.xyratex.com [mailto:david_inst...@uk.xyratex.com]
Sent: Wednesday, January 12, 2000 9:52 AM
To: emc-p...@ieee.org
Subject: Re: What is Fire-wire?
Dear answerers,
thanks for your kind help.
The real cases have been VERY useful. If you have more of them, please send
the values to me.
Thanks again.
David
-
This message is coming from the emc-pstc discussion list.
To cancel your subscription, send mail to majord...@ieee.org
Hi Pryor,
I have no Egyptian experiance but my archive says, that on 01.11.99 Ron
Pickard/Hypercom/US [rpick...@hypercom.com] answered a question about Egypt:
Contact the following agencies for further details:
EGYPT TELECOM
Ramses Street
Cairo 11511 EGYPT
There is also the 'hybrid' transient suppressor, an assembly consisting of a
gas discharge tube, followed by a series resistor (or inductor), followed by
a suppression diode. As mentioned by Robert, the gas tube takes time to
operate, during which the pulse voltage can rise to hundreds of volts.
Hi Paul
Part 20.3.1 of UL6500 states Materials shall have properties as shown in
Table VIII.
Table VIII gives a list of specific parts (items 1 - 10) and then item 11)
gives a minimum requirement of Materials used in applications other than
those specified in items 1 - 10 as 94HB.
There is an
Hi Group.
This stuff is covered in the UK by BASEEFA rules, and the various areas
described variously as Ex and EEx etc.
As an aside, whenever I have designed Intrisically safe equipment, I have
left behind all the EEx equipment, the BASEEFA approved housings, the
safety relays, and Zener
Ken Javor wrote:
When choosing transient suppression for power line input to equipment, what
are the choices (MOVs, silicon TVS, glass discharge tubes, others) and what
are the trade-offs? Thank you.
Hello Ken,
Here are some typical device types I've come across for transient
suppression:
Ken,
Rule of thumb which hopefully is accurate:
MOV's have a discrete lifetime (like 10 cycles at full rating) before
they're gone.
In order of joules absorbed versus package size:
Glass tubes, MOV's, silicon (from huskiest to weakest)
For turn on time:
silicon, MOV's, glass tubes (from
41 matches
Mail list logo
