Tom Gray on tue 27 aug 96
Here's a question for all the pyro/techno/whiz's on this list.
Why does a digital pyrometer register inaccurately at higher temps.? Is
it because of some ambient air factor? Or is it because the kiln
interior never reaches a true 2380 F.(at ^10). Is this a time/temp.
curve thing? At bisque temps. My pyrometer reads pretty close to
accurate (1830)-but at ^10 it reads 2260. Any ideas?
Tom Gray
Seagrove, NC
http://ns.atomic.net/~tgraypots
Jonathan Kaplan on tue 27 aug 96
>----------------------------Original message----------------------------
>Here's a question for all the pyro/techno/whiz's on this list.
>Why does a digital pyrometer register inaccurately at higher temps.? Is
>it because of some ambient air factor? Or is it because the kiln
>interior never reaches a true 2380 F.(at ^10). Is this a time/temp.
>curve thing? At bisque temps. My pyrometer reads pretty close to
>accurate (1830)-but at ^10 it reads 2260. Any ideas?
>Tom Gray
>Seagrove, NC
>http://ns.atomic.net/~tgraypots
Tom: Its the thermocouple. Providing you have a quality digial meter and
the run from the thermocouple to the meter is compensated for, the quality
of the thermocoupole is the link in the system that could be responsible
for the innaccurate readings. Seems as if type K thermocouples are pretty
standard on most pottery equipment, which may not provide the accuracy you
need. The platinum thermocouple on my oxygen probe is very accurate at both
low an high temperatures and shows about a 50 degree diffferential to the
type K unit on the controller. I have re programmed the controller to the
probe to compensate for this and it works fine.
Check out materials from Omega Engineering or Nanmac.
Jonathan
Jonathan Kaplan
Ceramic Design Group Ltd./Production Services
PO Box 775112
Steamboat Springs CO 80477
(970) 879-9139*voice and fax * email jonathan@csn.net
"Show up, pay attention, be a good listener, tell the truth, don't be
attatched to the results!"
WardBurner@aol.com on tue 27 aug 96
Tom,
I think your guess may be right about the time/temp curve. My guess is that
you have a pretty slow firing. If not, and you fire fast, the pyrometer
should read higher than the Orton number for cone 10. We fire fast to cone 6
(400F an hour) and my pyrometer reads about 30 F higher than the cone guide.
If this doesn't match what's going on with you, I would replace the
thermocouple first. If you do alot of reduction, the ole thing may be worn
out.
Marc Ward
Ward Burner Systems
PO Box 333
Dandridge, TN 37725
USA
423.397.2914 voice
423.397.1253 fax
wardburner@aol.com
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