Hi all.
From: Bill Owsley
Sent: Friday, August 24, 2007 5:40 AM
Have you ever reversed the current across one of these and
noticed the junction gets cold?
Actually, it gets hot! At least one of the materials gets hotter, and one
gets cooler, the net effect being positive.
If you make the
the Seebeck Effect and Peltier Effect are supposed to be
essentially the inverse of one another, this might prove an interesting
experiment. Although, the voltages involved in thermocouples is smaller
than any power supply I have in my lab can regulate to.
Two identical thermocouple types
experiment. Although, the voltages involved in thermocouples is
smaller than any power supply I have in my lab can regulate to.
You don't need a very low voltage. Just put a resistor in series - a
lamp would give you some regulation of the current but it is unlikely to
be necessary.
The cooling
experiment. Although, the voltages involved in thermocouples is smaller
than any power supply I have in my lab can regulate to.
Two identical thermocouple types with the beads in intimate contact with
one another. Welding into a single bead might even be OK. Apply an
appropriate voltage to one pair
I weld thermocouples, but I've seen
instructions on welding that say to do so.
The point nearest the 'free' ends of the thermocouple wire is where the
temperature will be measured and will act as the junction. If a twist
is a cm long, there's probably 9 mm of irrelevant (to temperature
measurement
the topic was posted.
Sort of like watching the Discovery Channel, while at work...
Best Regards,
Patrick.
p.con...@hp.com
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of John Woodgate
Sent: Friday, August 24, 2007 9:38 AM
To: emc-p...@ieee.org
Subject: Re: thermocouples
In message
09c2d42ff0bfca4b829cdbe89b8f66ff0135d...@g3w0637.americas.hpqcorp.net,
dated Fri, 24 Aug 2007, Conway, Patrick R (Houston) p.con...@hp.com
writes:
the next time a Mech. Engr. complains to me about the black magic of
EMI, I can explain that EMI is actually an extension of
... :)
Best Regards,
Patrick.
p.con...@hp.com
_
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Bill Owsley
Sent: Friday, August 24, 2007 7:40 AM
To: don_borow...@selinc.com; emc-p...@ieee.org
Subject: RE: thermocouples
Have you ever reversed the current across one
xantrex.com To
Sent by:
emc-p...@ieee.org cc
Subject
08/23/2007 12:25 RE: thermocouples
PM
I say that the voltage is generated at the junction of the wires, but the
wires should conduct some heat away from the junction. I expect that the
error is typically small, but it and other
In message
5f5a140eb5cb094bb4d2c477c8c4ad9923f...@sjc1amfpew04.am.sanm.corp,
dated Thu, 23 Aug 2007, Tarver, Peter peter.tar...@sanmina-sci.com
writes:
In a practical sense, for solder be effective, you probably need a
solder pot, a flux and a short, neatly twisted tip at the end of the
Here is a good explanation of thermocouple
theory:
http://sensortecinc.com/docs/technical_resources/Thermocouple_Theory.pdf
Best regards,
Rich
Richard Nute
Product Safety Consultant
San Diego
Tel: 858-592-2620
FAX: 858-592-2620
Mobile: 858-776-1618
e-mail: ri...@ieee.org
-
I'd welcome an off-the-list discussion.
From: John Woodgate
Sent: Thursday, August 23, 2007 11:34 AM
Tarver, Peter writes:
For accurate information on the underlying principles of how
thermocouples work, perform searches on Seebeck Effect.
There's a long tale about this, which is OT
other than at
the junction or dislodged/ misplaced thermocouples.
I have been able to justify the use of thermal crayons, infrared imaging
and touch provided measurement tolerance was taken into account. Be
willing to argue your point with the inspector if necessary.
Bob Johnson
Ralph McDiarmid
cc
Subject
08/23/2007 12:25 RE: thermocouples
PM
In message
de87437fe365cb458c265ea3d73b6f1d027c0...@xbc-mail1.xantrex.com, dated
Thu, 23 Aug 2007, Ralph McDiarmid ralph.mcdiar...@xantrex.com writes:
I say that the voltage is generated at the junction of the wires, but
the wires should conduct some heat away from the junction.
I agree with
.
Ralph McDiarmid, AScT
Compliance Engineering Group
Xantrex Technology Inc
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of John Woodgate
Sent: Thursday, August 23, 2007 11:34 AM
To: emc-p...@ieee.org
Subject: Re: thermocouples
In message
5f5a140eb5cb094bb4d2c477c8c4ad9923f
In message
5f5a140eb5cb094bb4d2c477c8c4ad9923f...@sjc1amfpew04.am.sanm.corp,
dated Thu, 23 Aug 2007, Tarver, Peter peter.tar...@sanmina-sci.com
writes:
With all due respect to 'the experts,' the article pointed to contains
inadequate and misleading description of what makes thermocouples work
solder or weld the thermocouples. In a
practical sense, for solder be effective, you probably need a solder
pot, a flux and a short, neatly twisted tip at the end of the
thermocouple wires. I mention this, because using a soldering iron will
leave a blob that's probably too big to be useful and can
From: John Woodgate
Sent: Wednesday, August 22, 2007 1:35 PM
you could look at:
http://www.sensorland.com/HowPage017.html
With all due respect to 'the experts,' the article pointed to contains
inadequate and misleading description of what makes thermocouples work.
For accurate information
don't think that IEC 60065 and IEC 60950-1 specify welded
thermocouples, or thermocouples at all. The methods of measuring
temperature are, with a very few exceptions, not specified.
I find that if you have the inclination, committee involvement is of
benefit.
I would agree with that, in general
Brian,
Why struggle with it? I have found that by far the simplest approach is to
just buy new welded thermocouples and throw them away when they fail. For
general purpose thermocouples such as T-type, the cost is simply not worth
the time and effort of welding your own. For the cost of a good
Collins, Colorado USA 80525
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Brian
O'Connell
Sent: Wednesday, August 22, 2007 2:14 PM
To: 'EMC-PSTC - Forum'
Subject: thermocouples
Good People,
In accordance with my accreditations with the various agencies (SMT.
TMP,
Cat Cert
In message 01c7e4f8$ffc680d0$d600a...@tamuracorp.com, dated Wed,
22 Aug 2007, Brian O'Connell oconne...@tamuracorp.com writes:
So how do I convince the agencies to continue to accept my data if I
convert to a soldered t/c junction ?
You probably don't. Welded junctions are a sacred cow.
Good People,
In accordance with my accreditations with the various agencies (SMT. TMP,
Cat Cert, CTDP, etc), I have religiously followed their guidelines and
requirements for thermocouple welding and application technique.
But, the technicians and engineers continue to have problems with
I read in !emc-pstc that Haynes, Tim (UK Stanmore)
tim.hay...@baesystems.com wrote (in F4757F038CDD79499CF1F293240924791
5b...@glkms0005.greenlnk.net) about 'Thermocouples' on Wed, 28 Apr
2004:
Argon would be released around the thermocouple and a discharge initiated
that
would weld the two
consistent results using a C block. What is your set-up
?
Brian
-Original Message-
From: Mobers Jan (ST-VS/ENG1) [ mailto:jan.mob...@nl.bosch.com]
Sent: Wednesday, April 28, 2004 6:35 AM
To: emc-p...@majordomo.ieee.org
Subject: RE: thermocouples
Hello Brian,
You mentioned that you
Hello Brian,
You mentioned that you welding the thermocouples by yourself. Please can you
explain how do you do welding the thermocouples.
I do this with a DC loaded Capacitor and a carbon bar.
Best Regards
Jan Mobers
-Original Message-
From: owner-emc-p...@majordomo.ieee.org
An error from IEEE, so try again.
Empirical measurements using type T and K thermocouples, welded in inert noble
(argon) gas, as read by an HP 34970, and compared to thermocouple junctions
formed by mechanical twist, solder, and ambient-air weld; and buried in
separate wells, approx 1cm depth x
Hi All,
In the '70's, I used to weld the cores of a mineral insulated, stainless steel
sheathed thermocouple. The OD of the thermocouple was as small as 2mm. I
worked on the design of the capacitor discharge welder. The thermocouple pair
were Pt/PtRh.
A rough outline of the process is as
30 years ago I watched a major safety NRTL (you may be able to guess
which one) weld thermocouples - be glad you didn't get the job doing that.
Basically, the whole apparatus consisted of a pencil stub, a high current
power supply, a bare contact, an open pool of mercury and a light bulb
I weld my own thermocouples and yesterday reflected on
discussions in this list regarding acceptability of
thermocouple welds to third party safety agencies. There is
an apparent conflict in the lore of thermocouple welding and
the fundamental theory of operation for thermocouples that I
am
Omega has a good reference available on their web site.
http://www.omega.com/temperature/Z/pdf/z204-206.pdf
They also have plenty of good information on the properties and uses of
thermocouples.
http://www.omega.com/temperature/Z/zsection.asp
Ted Eckert
Regulatory Compliance Engineer
American
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