I have received several requests for a compilation of all of the responses I
got to my request for information on high quality computers for use as
Emissions test beds. The responses are included below:
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Randy:
As one of the EMI engineers who helped design their new chassis, I
must say that I agree with your assessment of the new OptiPlex
chassis. The chassis used for their Dimension line is still quite good
for use as a test bed as it is of more conventional construction.
Ross Carlton
Harris Corp.
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We use a HP Vetra for testing. The one I have is couple years old
but the new ones are rummored to be as good as this one. It is typically
10db below the Class B limit. It's case is hard to get off as it has
lot's of fingers. (continous). I do not know anything about the other
HP models, just the Vectra's which are hard to find.
Jim
Jim Bacher, Senior Engineer _\\|//_ Monarch Marking Systems, Inc.
email:[email protected] (' O-O ') voice:1-937-865-2020
PO Box 608--------------------ooO-(_)-Ooo------------fax:1-937-865-2048
Dayton, Ohio 45401-0608---|---|---|---|---|---|---|---|---|---|---|---|
170 Monarch Ln., Miamisburg, Ohio [email protected]
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Randy, Power Computing makes an all-metal tower-type chassis with
grounding fingers at the opening for the fences. I haven't gotten to take
any of their systems to the OATS, since I've been pretty happy with the
HP Vectra 500 and Power Mac 7200/90 I've been using. I have heard from a
couple of people that they are pretty clean.
The drawback for most companies with the Mac or Power Computing systems
is that you have to get your Mac firmware up and running fast (I don't
have that problem, my Mac guys are sharp and usually get their stuff
running before the PC, SGI, or Sun guys).
Steve Chin
StreamLogic Corp.
Menlo Park, CA, USA
[email protected]
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Randy,
I have had very good results with a Digital Celebris XL590 PC. The
enclosure is extremely well done and it does have EMI fingers on the card
slots. This system (90 Mhz, I think) is now obsolete, but I assume their
later generation products are also good. Please let me know how you make
out with your testing.
STYLE/MODEL/
UNIT NAME PART NO
========= ============
Digital Monitor VRT17-HA
Digital PC 873WW
HP Thinkjet Prt 2225CT
Digital Mouse m/n M-S35
p/n PCXAS-AD
Max Kelson, Peripherals Engineer
[email protected]
Evans & Sutherland Computer Corp.
***********************
Randy,
We're using the following:
Toshiba Infinia 7161
Very good for Class B, has very low commmon mode emissions, though
the mouse is a little quirky during ESD tests but passes. All metal
enclosure and cover with plastic cosmetic overlays, tower style.
Includes Universal Serial Bus, which also passes EMC. You'll have to
remove the plastic cosmetic back cover if you need to switch from 115
to 230 VAC often. Too new for a long-term immunity assesment, but
this particular unit was not CE marked (which explains the mouse);
the current production models (we've seen it) are CE marked (on the
bottom). (Make sure of this if you decide to get one.) We're
considering buying another real soon.
HP VL2 5/60
No longer available but you might find them 2nd hand. Easy cover
removal, though uses a riser board which makes common mode emissions
noticable. We have two, one is fair for Class B, the other is only
passing Class A; the difference is not explained. They have endured
test after test without hardware failure on the main unit, the mice
last about a year then it seems their cables degrade too much to pass
emissions; but that's easy to fix by getting a new mouse.
Dell XPS P60, or P60d
Also no longer available, fair for Class B. Uses an all metal
enclosure - no plastic, no riser style daughter boards. A bother to
get in/out of, held in place with screws. Just don't let any of the
HD/FD/CDROM drive ribbon cables lay near the cache RAM area. Like
the HPs they have sustained many tests without breaking down.
Dell XPS P100c
Likely not available, same construction as the XPS P60 cabinet - no
plastic. Same cable caveat.
Digital Celebris 466
Out of production for almost two years now, was a very well built
cabinet for EMC - which also explains why Digital couldn't compete
with the other junk on the market. Easy cover removal, low emissions
even though it had a riser daughter baord. Good for Class B;
motherboard (in our case) didn't endure the immunity tests for too
long. It failed for the third time and is now filling space under my
desk.
We find that our software people tend to upgrade their systems
frequently, so we always watch for one of these systems (like the
Dells) becoming available - or we trade failing systems that
otherwise function; like the two new Compaq DeskPro 2000s we bought
that didn't pass Class B emissions and had out-of-spec ISA hardware
slots.
Yes, the plastic base Dells are very bad news; they might pass
initially, but the typical extra handling an EMC test host gets, and
cover on/off cycles, degrades the conductive coatings rapidly.
Regards,
Eric Lifsey
National Instruments
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Randy
I recently asked this question to the test house Instrument Specialties
(Delaware Watergap, Pa.) and they suggested HP (vectra?) desk top PCs.
This makes sense since HP is involved in emission detecting equipment.
Test Eng. Joe Hiens now at Chase in NJ may be able to give you more
feedback. Sorry I don't have their ph# and he presently isn't on the web.
He said that card manufactures commonly use the HP platform because it is
so quite and he implied that the housing was part of it. Perhaps good for
your needs.
Hope this helps
Chris Wells
Sr Des. Eng.
Cutler-Hammer
*************************
I have used the new DEC Alphas (sp?) with much success in testing our PCI
boards.
eric
[email protected]
