-----Original Message-----
From: Chris Maxwell [mailto:chris.maxw...@nettest.com]
Sent: Monday, January 07, 2002 9:20 AM
To: Crabb, John; emc-p...@majordomo.ieee.org
Subject: Re: Thermocouple alternative?
John,
We use T-type thermocouples which are not as ferrous as J and K types, and
therefore not as susceptible to electromagnetic fields. Still, we run into
problems (we make high-power switching power supplies, by the way).
Sometimes noise is coupled into the thermocouple wire. I have fixed this
with a choke in the past.
I have had difficulty convincing agencies to accept data from non-contact
thermal measurement systems, e.g., infrared or optical. The way that I have
convinced them is to take side-by-side measurements on something that is not
producing strong fields using a thermocouple and the non-contact measuring
device. When they saw that the two devices measured the same temperature,
they were satisfied.
Good Luck,
Jeff Jenkins
Advanced Energy Industries, Inc.
Fort Collins, CO
> -----Original Message-----
> From: Crabb, John [SMTP:jo...@exchange.scotland.ncr.com]
> Sent: Monday, January 07, 2002 9:02 AM
> To: emc-p...@majordomo.ieee.org
> Subject: RE: EMC-related safety issues
>
> Seeing that we have got round to the subject of thermocouples, etc, I
> often
> use a Solartron SI3535D datalogger with thermocouples for measuring
> component temperatures, and find quite often that it does not give
> "correct"
> readings when thermocouples are placed on transformers in switching
> power supplies, high voltage transformers in monitors, etc. I can get
> a
> "correct" reading by switching off the EUT momentarily, obviously
> removing the source of the problem. Note that the problem can occur
> even if the thermocouple is not making an electrical connection to the
> component winding involved.
>
> Any suggestions how to overcome this ? My previous antique datalogger
> didn't have this problem, but it eventually had to be scrapped due to
> lack
> of spare parts - and the expectation that a more modern unit would be
> better !.
>
> Regards,
> John Crabb, Development Excellence (Product Safety) ,
> NCR Financial Solutions Group Ltd., Kingsway West, Dundee, Scotland.
> DD2 3XX
> E-Mail :john.cr...@scotland.ncr.com
> Tel: +44 (0)1382-592289 (direct ). Fax +44 (0)1382-622243.
> VoicePlus 6-341-2289.
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