Stanley Irvin on wed 25 aug 99
clayarters,
I recently purchased a Fluke digital pyrometer and have found it very
helpful in terms of controling top and bottom kiln temperatures and keeping
on top of my firing schedule. It seems to give very accurate readings
until I get to about 2000 degrees F where it begings to read lower that
what cones indicate. By the time I reach cone 10 (reduction) it reads
about 150 degrees off compared with the cone reading. I spoke to the Fluke
representative about the problem and he indicated that there might be a
small electrical current being generated during the firing between the top
and bottom thermocouple that would throw the reading off by that much.
Apparently the solution would be to ground the negative lead of the
thermocouples to the kiln frame, assuming the kiln is grounded also, to fix
the problem. I havn't had a chance to try this yet but was wondering if
anyone else had had this problem. Other than the temp. being off toward
the end of the firing, the pyrometer is still very useful in terms of
indicating top and bottom temperature differences and rate of rise or fall
in temperatures. Looking forward to hearing from anyone out there who has
any suggestions.
Thanks!
Stan
St. Edward's University
Austin, Texas
David Woodin on thu 26 aug 99
Assuming that you are taking time and temperature into consideration, as to
what the temperature is that the cones are falling at, then what I did to
solve this type of problem is to get ungrounded thermocouples. Omega is one
of the sources for thermocouples, just make sure they are the Omega superclad
type K.
David
Richard Gralnik on thu 26 aug 99
Stan,
This could be the dreaded K type thermometer inaccuracy above F2K (grin).
Also, is your fluke rated to temps above 2000 degF? I bought an omega
digital thermometer that goes to 2500. They have one rated to 2000 but I
was told not to buy it since I need to go higher than that.
By the way, I bought a THICK (1/8" diameter) K thermocouple from Paul
Geil. He assures me it will do just fine to C10 temps for some time. Add
to that Nils Lou's recommendation to coat the thing with ITC213 to extend
its life and I think I'm in pretty good shape for $28 vs. $200+ for a platinum/
rhodium type R or S thermocouple.
Richard
At 04:58 PM 8/25/99 -0400, you wrote:
>----------------------------Original message----------------------------
>clayarters,
>I recently purchased a Fluke digital pyrometer and have found it very
>helpful in terms of controling top and bottom kiln temperatures and keeping
>on top of my firing schedule. It seems to give very accurate readings
>until I get to about 2000 degrees F where it begings to read lower that
>what cones indicate. By the time I reach cone 10 (reduction) it reads
>about 150 degrees off compared with the cone reading. I spoke to the Fluke
>representative about the problem and he indicated that there might be a
>small electrical current being generated during the firing between the top
>and bottom thermocouple that would throw the reading off by that much.
>Apparently the solution would be to ground the negative lead of the
>thermocouples to the kiln frame, assuming the kiln is grounded also, to fix
>the problem. I havn't had a chance to try this yet but was wondering if
>anyone else had had this problem. Other than the temp. being off toward
>the end of the firing, the pyrometer is still very useful in terms of
>indicating top and bottom temperature differences and rate of rise or fall
>in temperatures. Looking forward to hearing from anyone out there who has
>any suggestions.
>
>Thanks!
>Stan
>St. Edward's University
>Austin, Texas
| |
|
