Perhaps if the added cost of a reliable ground connection is presented to
management as "insurance" from future problems and litigation they will be
more willing to accept it. And if you could present a product liability case
that supports your case, that will help some more.
Dave Cuthbert
Micron Technology
From: [email protected]
[mailto:[email protected]]On Behalf Of Price, Ed
Sent: Monday, November 17, 2003 8:07 AM
To: '[email protected]'
Subject: RE: Grounding
>-----Original Message-----
>From: Gary McInturff [ mailto:[email protected]]
>Sent: Friday, November 14, 2003 10:46 AM
>To: 'Crabb, John'; Ned Devine; IEEE EMC/Product Safety (IEEE,
>EMC/Product Safety)
>Subject: RE: Grounding
>
>
>
>John,
> You are correct, but you have just presented the
>conundrum of the
>thread.
> "Reliably grounded" can be determined through test - 25
>or 30 amps
>for a minute. A new hinge will likely pass that test. A "used" one may
>likely fail because of the corrosion and wear discussed by
>others. So the
>conundrum is do you test to get through the standard or do you use the
>standard to help you design something which hopefully remains safe.
> Personally, I don't like hinges for grounds - PE or
>earth and for
>the very cost sensitive it can be a real issue with the
>management guys and
>bean counters.
> Gary
>
FWIW, military practice doesn't allow grounding through a hinge.
MIL-HANDBOOK-454A, Paragraph 4.5.2.2 says "Ground connections to shields,
hinges, and other mechanical parts should not be used to complete electrical
circuits." It goes on to also say "...the ground should be continuous and
permanent."
Paragraph 4.5.2.3 specifically addresses hinged panels and doors, saying
"Hinges or slides should not be used for grounding paths. Panels and doors
containing meters, switches, test points, etc., should be attached or hinged
in such a manner as to insure that they are at the same ground potential as
the equipment in which they are mounted, whether in a closed or open position.
A ground should be considered satisfactory if the electrical connection
between the door or panel and the system tie point exhibits a resistance of
0.1 ohm or less and has sufficient capacity to insure the reliable and
immediate tripping of equipment over-current protection devices."
Of course, this isn't a commercial requirement, but it defines what the
military thinks is necessary to avoid problems.
Ed
Ed Price
[email protected] WB6WSN
NARTE Certified EMC Engineer & Technician
Electromagnetic Compatibility Lab
Cubic Defense Applications
San Diego, CA USA
858-505-2780 (Voice)
858-505-1583 (Fax)
Military & Avionics EMC Is Our Specialty
