On Wed, 30 Mar 2005 23:32:56 GMT, "Ken Finney"
wrote:


I knew I was too close to the problem, and that there had to be a simple
solution. Your solution is likely what we will use.

As for the why, we are testing a switch to ensure it won't set off an
explosive atmosphere. The test method isn't too clear other than we need to
test the switch at maximum current into an inductive load. Rather than try
to justify why this really means "a partially inductive load", we'd rather
worst-case the test conditions.

If you're dealing with explosive atmospheres, you'd better hire
someone who knows what they're doing to do the testing and certify
the results -- or perhaps tell you to walk away from this one.
12 amps and 28 volts are way far out of intrinsically safe territory
with any switch or other device.

Please have a look at figure four in the following, which addresses
circuits with no inductance but only resistance:
http://www.crouse-hinds.com/CrouseHi...fm?CompanyID=1

I strongly agree with Jeff Wisnia here. You should definitely get
competent professional counsel rather than rely on opinions from
guys on a newsgroup who are not accountable if/when your switch blows
something up.