John-
Thanks for the info about swapping out CPU's.
Be careful about declaring a the CPU's as more sensitive. It may be
that
they was never tested - here is what I mean: your setup may be different from
the "generic" setup used to test/qualify CPU's. It could be that the CPU's
pass all tests in a standard "generic" test configuration. But if you test
configuration is different then the performance can also be different.
One big difference is your stainless mouse. Most PC's are not sold with
stainless steel mice. The generic PC mouse has a plastic shell and a plastic
shell does not require contact discharge testing. Therefore you may be the
first person to perform a contact discharge test on devices connected to that
port.
Sounds like you have an interesting case of putting two passing
components
together, and creating a non-passing system. This is a great real-world
example. Please keep the list updated with your findings.
From: [email protected] [mailto:[email protected]] On Behalf Of John Cochran
Sent: Wednesday, January 06, 2010 1:10 PM
To: [email protected]
Subject: RE: [PSES] ESD Test Failure of Stainless USB Mouse
One of my problems in solving this problem is that the industrial computers we
use, pass the ESD tests with this mouse. The 2 systems that are failing have
Dell computers. One is a Dell Optiplex 760 and the other is a Dell rack-mount
server. I don't know if better grounding was used on the industrial
motherboards and chassis, or if the Dell computers are more sensitive to ESD
events. It appears from testing that we are not grounding the cable shield as
it enters the stainless steel enclosure. A separate ground wire was attached
to the mouse shell, then to the enclosure, which passed the ESD tests. I have
some components ordered which should help me ground the cable shield to the
enclosure, just inside the enclosure entry point. I know that a feed-through
grounded cable gland would be preferred, but it aesthetically does not look
good. I'll let you know if it works, but I definitely will test to see at
what level it fails, like Doug suggested.
Thanks,
John
From: [email protected] [mailto:[email protected]] On Behalf Of Doug Smith
Sent: Wednesday, January 06, 2010 1:16 PM
To: John Woodgate
Cc: [email protected]
Subject: Re: [PSES] ESD Test Failure of Stainless USB Mouse
Hi Everyone,
Just a thought on ESD testing. The actual failure level should always be
determined, not just that the test was not passed. For instance, suppose
you are trying for 4 kV contact mode but fail and the failure happens at
1.5 kV. You try something, but unit still fails. However, the failure
level increased to 3 kV. This is very important. Either more of the same
technique should be tried or you have peeled one layer of the ESD onion
and now another mechanism controls the response. I recently had a
product that had three distinct mechanisms and all had to be fixed
simultaneously for the product to work. A solution would never happen if
one tried experiments one at a time and just looking at the pass-fail
state on a product like this.
Doug
On 1/6/10 7:06 AM, John Woodgate wrote:
> In message
> <769907F0D19EFA45BD6F04FC6E896D6D220970D160@GVW0538EXC.americas.hpqcorp.n
> et>, dated Wed, 6 Jan 2010, "Conway, Patrick R (bNB Houston)"
> <[email protected]> writes:
>
>> 1- Keeping all other parameters the same, swap the mouse,
>> re-test, then swap the PC, and re-test.
>>
>> a. use a completely different mouse type and completely
>> different PC.
>>
>> b. Try to determine if the problem follows the mouse or follows
>> the PC.
>
> If totally confused, change the test gear. (;-)
--
___ _ Doug Smith
\ / ) P.O. Box 1457
========= Los Gatos, CA 95031-1457
_ / \ / \ _ TEL/FAX: 408-356-4186/358-3799
/ /\ \ ] / /\ \ Mobile: 408-858-4528
| q-----( ) | o | Email: [email protected]
\ _ / ] \ _ / Website: http://www.dsmith.org
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