Mary White on wed 13 aug 03
I have been relying on my analog pyrometer and getting runny glazes
and glazes shinier than I want. My electric kiln only has two
peepholes, one so near the bottom that if there's a shelf on posts
even as small as 1" the peephole is covered, so it's useless, and the
other where I put the pyrometer probe, so I haven't been using
witness cones. Even if I use a kilnsitter cone a number higher than I
want the kiln still turns off long before the pyrometer is saying it
should.
Yesterday I did a bisque, put the ware directly on the bottom instead
of using a shelf, so I used that hole for the pyrometer and put
witness cones at the other hole. I was aiming for ^06, used a ^05 in
the sitter. So I'm aiming for 1830 but when the sitter tripped the
pyrometer said 1675! Instead of resetting the sitter and continuing
to 1830 on the pyrometer, as I usually do, I just let it quit. I
couldn't see the cones at that point but when I unpacked the kiln the
next day they were perfect, ^07 and ^06 down but ^05 still standing.
So my pyrometer's seriously out of whack. It was new about a year ago
and I haven't fired with it more than 8 times. I'd like to test it
and calibrate it properly. Does anyone have any advice on this?
If I can get this fixed I'll definitely get a proper separate hole
drilled for the pyrometer so I can use witness cones every time.
Thanks,
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mary
on the wet west coast of British Columbia
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--
Mary White
HARBOUR PUBLISHING
Box 219
Madeira Park, BC
V0N 2H0
------------------
Publishers of the Encyclopedia of British Columbia.
Visit the Encyclopedia website at http://www.knowbc.com.
Earl Krueger on wed 13 aug 03
On Wednesday, August 13, 2003, at 05:41 PM, Mary White wrote:
> If I can get this fixed I'll definitely get a proper separate hole
> drilled for the pyrometer so I can use witness cones every time.
First thing I did was drill a hole through the side of my kiln.
Trivial !
Just do it.
Earl...
WHC228@AOL.COM on thu 14 aug 03
If your meter needs calibrated send it to Cleveland Electric Labs In
Cleveland Ohio.
Also send the thermocouple that you intend to use with it. If it is a K type
couple I would start with a fresh one. K type couples when fired to high
temperatures do not last too long. They begin to fail slowly and will tell the
meter incorrect information for a long time before they quit completely. If you
can afford to make the change use an S type couple. Your meter will have to be
reset, or you may need a different meter that will work at the voltages that
the S couples range is in.
I can't recommend using an S couple enough. I have some in my kilns that have
gone to cone ten every other day for the past fifteen years. I have them
coupled to my kiln controller, so it is important that they work.
Bill Campbell
piedpotterhamelin@COMCAST.NET on thu 14 aug 03
Mary,
You could have a broken or loose thermocouple-wire connection depending on the
type of probe that you have. The older styles of probes have the thermocouple
and wire meeting in a square porcelain block with four set screws to anchor
them together. Loosen and remove everything and then put them back together
again, screwing the whole thing tightly together. Lock the wires onto the rods.
If the probe is of the single rod type, still check out the area where they
are joined for breaks in the wire or a broken braze. Also check the back of
the pyrometer where the wires connect for a loose connection.
It doesn't hurt to have another probe on hand when you need it. You can pick
up a rotary thermocouple switch on ebay and with it, you will be able to use
both probes and read the temperature of different zones off of just one
pyrometer. Or put both probes in one peephole to check accuracy.
Rick
> I have been relying on my analog pyrometer and getting runny glazes
> and glazes shinier than I want. My electric kiln only has two
> peepholes, one so near the bottom that if there's a shelf on posts
> even as small as 1" the peephole is covered, so it's useless, and the
> other where I put the pyrometer probe, so I haven't been using
> witness cones. Even if I use a kilnsitter cone a number higher than I
> want the kiln still turns off long before the pyrometer is saying it
> should.
>
> Yesterday I did a bisque, put the ware directly on the bottom instead
> of using a shelf, so I used that hole for the pyrometer and put
> witness cones at the other hole. I was aiming for ^06, used a ^05 in
> the sitter. So I'm aiming for 1830 but when the sitter tripped the
> pyrometer said 1675! Instead of resetting the sitter and continuing
> to 1830 on the pyrometer, as I usually do, I just let it quit. I
> couldn't see the cones at that point but when I unpacked the kiln the
> next day they were perfect, ^07 and ^06 down but ^05 still standing.
>
> So my pyrometer's seriously out of whack. It was new about a year ago
> and I haven't fired with it more than 8 times. I'd like to test it
> and calibrate it properly. Does anyone have any advice on this?
>
> If I can get this fixed I'll definitely get a proper separate hole
> drilled for the pyrometer so I can use witness cones every time.
>
> Thanks,
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Mary
> on the wet west coast of British Columbia
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> --
>
> Mary White
> HARBOUR PUBLISHING
> Box 219
> Madeira Park, BC
> V0N 2H0
> ------------------
> Publishers of the Encyclopedia of British Columbia.
> Visit the Encyclopedia website at http://www.knowbc.com.
>
> ______________________________________________________________________________
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Steve Mills on fri 15 aug 03
Mary,
There is probably nothing wrong with your Pyrometer, it's just that
cones and pyrometers don't do the same thing: Pyrometers show you the
temperature inside the kiln as it is at the precise moment you look at
it. Cones however measure ACCUMULATED heat-work i.e the amount of heat
that has been absorbed by the cone (and by association your glazes)
during the time the kiln has been firing, a different animal altogether.
I used to take 17 hours to fire my 30 cube gas kiln to cone 9 in
reduction. As the cone went over the Pyrometer never read more than
1220o Centigrade. I had achieved enough heatwork to mature my glazes,
but at a lower overall temperature. If you fire your kiln at exactly
150o Centigrade per hour, there is a good chance the meter and cone will
agree as Orton Cones are calibrated at that rate of climb (as well as at
60oC per hour) However 150 degrees per hour might not be very good for
your work in the early stages of the firing.
Use the meter to tell you how fast (or not!) you are going, and the
cones to tell you when you've got there!
Steve
Bath
UK
In message , Mary White writes
>I have been relying on my analog pyrometer and getting runny glazes
>and glazes shinier than I want. My electric kiln only has two
>peepholes, one so near the bottom that if there's a shelf on posts
>even as small as 1" the peephole is covered, so it's useless, and the
>other where I put the pyrometer probe, so I haven't been using
>witness cones. Even if I use a kilnsitter cone a number higher than I
>want the kiln still turns off long before the pyrometer is saying it
>should.
>
>Yesterday I did a bisque, put the ware directly on the bottom instead
>of using a shelf, so I used that hole for the pyrometer and put
>witness cones at the other hole. I was aiming for ^06, used a ^05 in
>the sitter. So I'm aiming for 1830 but when the sitter tripped the
>pyrometer said 1675! Instead of resetting the sitter and continuing
>to 1830 on the pyrometer, as I usually do, I just let it quit. I
>couldn't see the cones at that point but when I unpacked the kiln the
>next day they were perfect, ^07 and ^06 down but ^05 still standing.
>
>So my pyrometer's seriously out of whack. It was new about a year ago
>and I haven't fired with it more than 8 times. I'd like to test it
>and calibrate it properly. Does anyone have any advice on this?
>
>If I can get this fixed I'll definitely get a proper separate hole
>drilled for the pyrometer so I can use witness cones every time.
>
>Thanks,
>
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Mary
>on the wet west coast of British Columbia
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>--
>
>Mary White
>HARBOUR PUBLISHING
>Box 219
>Madeira Park, BC
>V0N 2H0
>------------------
>Publishers of the Encyclopedia of British Columbia.
>Visit the Encyclopedia website at http://www.knowbc.com.
--
Steve Mills
Bath
UK
Paul Herman on sat 16 aug 03
Hello Bill,
I have a couple of questions about the S thermocouple. I've been using
the K until now and yes, they do go bad after a while.
Do you use the S thermocouple in a protective tube or bare?
I have an Omega hand held pyrometer. As far as I know, it only will read
the K orJ type. Are you saying that this instrument could be calibrated
to also read the S, or would I need a new one, specifically for the S?
And, what is the price range for an S thermocouple. They are made of
Platinum, arent they? My Ks (from Laguna Clay Co in LA) cost $12.00.
Thanks much,
Paul Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
----------
>From: WHC228@AOL.COM
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: Calibrating a pyrometer
>Date: Thu, Aug 14, 2003, 6:09 PM
>
> If your meter needs calibrated send it to Cleveland Electric Labs In
> Cleveland Ohio.
> Also send the thermocouple that you intend to use with it. If it is a K type
> couple I would start with a fresh one. K type couples when fired to high
> temperatures do not last too long. They begin to fail slowly and will tell the
> meter incorrect information for a long time before they quit completely. If
you
> can afford to make the change use an S type couple. Your meter will have to be
> reset, or you may need a different meter that will work at the voltages that
> the S couples range is in.
> I can't recommend using an S couple enough. I have some in my kilns that have
> gone to cone ten every other day for the past fifteen years. I have them
> coupled to my kiln controller, so it is important that they work.
> Bill Campbell
WHC228@AOL.COM on sun 17 aug 03
Paul
I use my thermocouples covered. I have no experience with an Omega meter, so
I can't answer whether it will be able to be used with the S couple.
For a long time I just used a multimeter from Radio Shack. The meter reads
out in millivolts so the numbers that you get are in volts rather than degrees.
There are charts that most people have if they have an Oxyprobe that will give
you the temperature in either C or F. If you are having trouble finding a
chart, write me and I will FAX you one.
The only place that I have ever gotten my S type couple is at Cleveland
Electric Labs.
It has been so long since I have had to buy them that I can't remember how
expensive that they were. I think about $100 or less though.
The multimeters are cheap, and they are digital. Much easier than trying to
read an analog meter.
I hope that I have answered your questions
Bill Campbell
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