Maggie Jones on tue 13 nov 07
Hello folks,
can anyone tell me..... what is the makeup of an S-type thermocouple?
I understand the K-type is magnesium with stainless steel sheath.
How does the S-type differ?
thanks,
still scrounging for the best deal on probe replacements. I am determined
to buy just the probe since the yellow connectors unscrew easily. ...I
have a wall mount controller, 3 zone.
maggie
http://TurtleIslandPottery.com
Maggie and Freeman Jones
Hank Murrow on tue 13 nov 07
On Nov 13, 2007, at 7:02 PM, Maggie Jones wrote:
> Hello folks,
> can anyone tell me..... what is the makeup of an S-type thermocouple?
> I understand the K-type is magnesium with stainless steel sheath.
> How does the S-type differ?
Dear Maggie;
Type S thermocouples are made up of Platinum on one side, and
Platinum/Rhodium on the other side of the weld. Heat creates an
electric current, which may be read with a meter(analogue or
digital). Because of the extremely high melting point of Platinum,
such type S thermocouples are much more reliable at temperatures
above cone 5, where the type K thermocouples based upon magnesium
will neither be accurate nor long lasting......... especially in
reduction atmospheres.
Cheers, Hank in Eugene.......... relaxing after the successful
opening of the Mingei show in Seattle last Saturday.
www.murrow.biz/hank
Jim Willett on wed 14 nov 07
On Tue, 13 Nov 2007 22:02:51 -0500, Maggie Jones wrote:
>Hello folks,
>can anyone tell me..... what is the makeup of an S-type thermocouple?
>I understand the K-type is magnesium with stainless steel sheath.
>How does the S-type differ?
Hi Maggie,
For a good explanation of thermocouple types and temperature ranges check:
http://instserv.com/rmocoupl.htm
Jim Willett
Out of the Fire Studio
http://www.outofthefirestudio.com
Hank Murrow on thu 15 nov 07
On Nov 13, 2007, at 7:02 PM, Maggie Jones wrote:
> Hello folks,
> can anyone tell me..... what is the makeup of an S-type thermocouple?
> I understand the K-type is magnesium with stainless steel sheath.
> How does the S-type differ?
Dear Maggie;
I was mistaken when I replied that the Type K was Magnesia...... it
is Chrome/Alumel. And the Type S is Platinum and Platinum/10%
Rhodium. The OxyProbe uses a type S thermocouple.
Cheers, Hank
www.murrow.biz/hank
Joseph Herbert on thu 15 nov 07
So, what about type N thermocouples?
Rated to 1300 C and without (it says) particular oxidation problems?
Don't know much about thermocouples but N sounds cheaper than anything with
platinum.
J
:
Joseph Herbert
Technical Writer
Irving, Texas
214-725-8305 (Cell)
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Fredrick Paget on thu 15 nov 07
The thread about thermocouples is getting more complete but one
thing has not been mentioned.
Thermocouples work on the fact that if wires of dissimilar metals are
joined at one end and heated there will be a small voltage generated
from that junction that can send a current through the wires to the
cold end .The lead wires from the thermocouple to the controller need
to be of a compatable alloy type to match the type of thermocouple
and the little plugs that often are used on them must be of matching
alloys too.Otherwise there are more junctions in the circuit that can
foul things up. If this is not attended to, a serious source of error
is introduced .
The type K use wire made of the same chrome alumnel alloys as the
probe so no extraneous metal to dissimilar metal junctions are
introduced.
Platinum thermoocouples (S and R) can not afford a matching platinum
lead wire since platinum wire is about the most expensive thing you
ever saw. Instead the thermocouple people have brewed up a cheap
alloy that is a close match around room temperatures.
So this means if you change to type S from K you need new lead wire
and plugs to match.
Fred
--
Twin Dragon Studio
Mill Valley, CA, USA
Ivor and Olive Lewis on thu 15 nov 07
Dear Hank Murrow,
Not sure who your informant is but Magnesium melts just below 650 Deg =
Celsius.
Type K couples comprise (Ni plus 10 Cr plus 1.5 Si ) V ( Ni plus 4.5 Si =
plus 0.1 Mg )
So the foundation element is Ni MP 1450 Deg C
Max service temp is 1300 deg C.=20
If they are mounted in an impervious sleeve Kiln atmosphere is of no =
consequence They cost me five bucks each so they are a disposable item.
Best regards,
Ivor
Jim Willett on thu 15 nov 07
One more note on thermocouples....if you are thinking you can just switch
types you can't. Your controller will be calibrated for the type of
thermocouple it was shipped with. Different types of thermocouples have
different milli volt outputs for the same temperatures. For instance a
type K at 1000 degrees C will read 41.3 mv. A type S at the same
temperature will only read 9.59 mv. The controller would think it was only
236 degrees C. If you are thinking of changing thermocouples make sure
your controller can be calibrated to the new type.
Jim Willett
Out of the Fire Studio
http://www.outofthefirestudio.com
Hank Murrow on thu 15 nov 07
On Nov 14, 2007, at 9:01 PM, Ivor and Olive Lewis wrote:
> Dear Hank Murrow,
> Not sure who your informant is but Magnesium melts just below 650
> Deg Celsius.
Dear Ivor;
Perhaps you took notice of my post today relating my chagrin in
incorrectly stating Mg as the type K. Of course, I should have said
it was Chrome/Alumel. I do stand by my statement that type S
thermocouples are better suited to duty in reducing atmospheres,
sleeved or not.
Cheers! Hank
www.murrow.biz/hank
Arnold Howard on thu 15 nov 07
From: "Jim Willett"
For instance a
> type K at 1000 degrees C will read 41.3 mv. A type S at
> the same
> temperature will only read 9.59 mv. The controller would
> think it was only
> 236 degrees C.
Jim, I'm glad you gave that warning. The opposite is also
true. If the controller is set for S-Type but a K-Type is
actually installed, the kiln will overfire.
The earlier controllers (Paragon 100 - 1000 series) accepted
only the K-Type. The Orton controller we are using now
accepts K, R, or S. The thermocouple type is selected with
the Options key.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
Maggie Jones on thu 15 nov 07
Ivor...5 bucks each?
please allow as to where you aquire a probe at 5$ each.?
Maggie
On Thu, 15 Nov 2007 15:31:44 +1030 Ivor and Olive Lewis
writes:
> Dear Hank Murrow,
> Not sure who your informant is but Magnesium melts just below 650
> Deg Celsius.
> Type K couples comprise (Ni plus 10 Cr plus 1.5 Si ) V ( Ni plus 4.5
> Si plus 0.1 Mg )
> So the foundation element is Ni MP 1450 Deg C
> Max service temp is 1300 deg C.
> If they are mounted in an impervious sleeve Kiln atmosphere is of no
> consequence They cost me five bucks each so they are a disposable
> item.
> Best regards,
> Ivor
>
>
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Ivor and Olive Lewis on fri 16 nov 07
Dear Maggie Jones,
I get mine from an industrial electronic supply company in Perth. they =
fit a dedicated Multimeter that cost me about $60 .
I suppose in the US Radio Shack would be the place to ask. Phil in eLV =
would know.
Best regards,
Ivor
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