Chris,
You may be correct that I was assuming a more complex situation than the
original poster intended. It won't be the first time this has happened.
However, I cannot entirely agree with your take on the situation.
In your post you mention:
I would assume that one of the conditions of using
Bob,
I read your initial response to this thread; and I think that your
understanding of the situation is more complicated than it really is.
I snipped the following from your response:
Nonetheless, you cannot possibly directly determine what the
temperature
change of
List-Post: emc-pstc@listserv.ieee.org
Date: May 14, 2002 (second Tuesday of the month)
Society Chapter: IEEE EMC Society
Subject: EMC REGULATIONS AND REGULATORS: WHAT'S NEW, WHO'S WHO
Speaker: Barbara Judge, Compliance Certification Services
Time: 5:30 Social, 7:00 Presentation
Place:
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présentation (in English) :
Wireless Healthcare Issues
Tomas Pavlasek, McGill University, Introduction
Donald Davis, McGill University, Volumetric 1.9-GHz fields
It appears that all these suggestions for finding temperature rise caused by
increasing conductor resistance, are based on the fallacy that there is a
direct relationship between the two. As indicated in an earlier post, this is
an incorrect supposition. The solution to the problem is far too
Bill/group
Let's check all these numbers.
Room temp of 20C? 68F (br). More like 25C, 77F.
Most people assume room temp is 297K (or is that 298?) which is more like
23.82C, ~75F (seems more reasonable), putting that into the linear equation
gives
234.5 +
Hi Robert / group
OK, Not the best choice of website to demo the answer. The differing
figures are because the formula has been transposed to give Temp from change
of R from the original formula which gives R from change of T. To do this,
another constant (The 234.5 constant) is required. This
Bill,
Thanks for the site.
Went there and found the same formula and constant I use.
For copper, Temp Coeff = 3.9 x 10-3
Then I clicked on table of coeff and there was a very long list of
materials, but the temp coeff of copper there was 6.8 x 10-3 ???!!!
Any ideas for this disparity?
Hi,
Thanks to all who responded. This seems to be the answer I was looking for.
Time to get out the physics book and do a little research.
Ned
Ned Devine
Program Manager
Entela, Inc.
3033 Madison Ave. SE
Grand Rapids, MI 49548
1 616 248 9671 Phone
1 616 574 9752 Fax
ndev...@entela.com e-mail
Hi Folks
Further to the answer given, here is a little more data.
The constant used is for the change of resistance with temperature. metals
and alloys (conductors) all exhibit a different constant. This can be used
for calculating temperature rise or resistance change. i.e. find the temp
rise
On Fri, 10 May 2002 12:57:16 +0200,
Kim Boll Jensen kimb...@post7.tele.dk wrote:
I have problems concerning clearance and creepage values in EN61010-1.
I have a product with a 24 ac and a 230 relay. The 24ac can be used for
sensors and are regarded as double insulated in the 230 Vac
If you plot resistance of copper vertically, against
temperature horizontally, and extend the graph
backwards, the point of intersection with the
horizontal axis is found to be -234.5 degrees C.
(Got this out of my early years text book which
I keep at my desk !)
Hence for a standard copper
Ned is referring to the constant used in the temperature rise calculated by
change in resistance formula ie
...
Where dt is the temperature rise, R1 is start resistance, R2 is end
resistance, T1 is start ambient and T2 is end ambient. 234.5 is the formula
constant for copper.
This formula
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