Linda Blossom on wed 28 feb 01
Susan,
I just recently took my probe apart too. The wire broke at the tip of the
thermocouple. It goes in one long thin space that runs down the inside of
the ceramic thermocouple, turns at the end , and comes out the other hole at
the top. There is one inside wire and one outside wire. This that broke
was the inside wire that is in the thermocouple. The other wire is on the
outside - it is the one you see before you take it apart. I took it to a
jeweler and he laser welded it so that there was no weld spot. It was
amazing. It cost me $30 and the repair job was worth it. I called and
explained what it was and that the wire was a thin platinum wire.
Linda Blossom
Ithaca, NY
Susan Ammann on wed 28 feb 01
After ever so carefully disassembling my oxy probe to repair a broken
thermocouple (fools rush in!) I realize I'm not real clear on exactly what
part of the platinum wire is supposed to be "twisted together" and then
heated until the wires melt together. There isn't a break anywhere along
the length of the wire...are the wires supposed to be joined together where
they emerge on the far end of the thermocouple tube? I embarked on this
repair project with the thought that "knowledge is power", but now I wish
I'd stuck with "ignorance is bliss" and sent it off to someone with some
expertise in repairing these things.
Has anyone on the list ever taken one of these things apart and then
repaired it? Care to share your genius?
Thanks.
Susan Ammann
Taos, NM
ammann@kitcarson.net
Susan Ammann on thu 1 mar 01
Linda,
Thanks for taking the time to answer. You've told me exactly what I
needed to know re. what part of the wire on the oxy probe to repair. After
thinking about it some, I guessed that somehow these two wires (presently
separate) somehow had to come together (couple as in thermocouple). But I
wasn't sure, and the directions from AIC aren't quite basic enough for
someone who's never worked on a thermocouple before.
Susan Ammann
Taos, New Mexico
ammann@kitcarson.net
Dennis Mummert on thu 1 mar 01
Susan. I don't own an oxyprobe (YET), but being half scientist, half
technician, half artist, and a whole bunch of other halves (some
say...half-baked); an oxyprobe will depend on two things to compute kiln
atmospheric oxygen. One is the current temperature, provided by the
thermocouple. The second is the resistance of the fine platinum wire.
Platinum has a well-understood resistance curve .vs. temperature, and as
such is used in precision laboratory instruments. The two numbers -
temperature from the thermocouple and the temperature the platinum
resistance wire should theoretically be equivalent. However, when the Pt
wire is exposed to a chemical atmosphere such as that in kiln exhaust gas,
its resistance will also change according to the concentration of conductive
ions. It is the *difference* between the two figures that is important.
The oxyprobe analyzer can simply subtract the two and look up the value for
O2 at that reading (correlated to present temperature). At any rate, this
is how I would design the instrument if I were doing laboratory flame
studies. I have done them, but not this method.
All that being said, if the platinum wire is broken, don't even attempt to
fix it. Anything you do to it will throw the reading off. Replace the wire
yourself, or have it done by the Oxyprobe people.
Incidentally, all US vehicles for the past 10 or so years have had oxygen
sensors mounted in the exhaust manifold. I don't have the specs for the
instrument, but it might be worth a bit of experimentation.
Dennis Mummert
Earthen Fire Studios
Fairborn, Ohio
http://users.erinet.com/30209
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Susan Ammann
Sent: Thursday, March 01, 2001 10:31 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: OXY Probe question
Linda,
Thanks for taking the time to answer. You've told me exactly what I
needed to know re. what part of the wire on the oxy probe to repair. After
thinking about it some, I guessed that somehow these two wires (presently
separate) somehow had to come together (couple as in thermocouple). But I
wasn't sure, and the directions from AIC aren't quite basic enough for
someone who's never worked on a thermocouple before.
Susan Ammann
Taos, New Mexico
ammann@kitcarson.net
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