Erik Harmon on wed 10 jan 07
>You seem to know a lot about this topic so I ask you, "What are the other errors >in a pyrometer reading and how can they be nullified? "
Dear Ivor Lewis,
I do not know nearly as much as I should. I would say the errors I have made have come from trusting various pyrometers too much or in the wrong situations. Its been a few years since I have fired a salt kiln but I do not think I have ever had a completely accurate reading once salt or soda has been introduced. Even after giving the atmosphere a chance to clear. The first two thermocouples that came with the my Skutt seemed to be horribly in accurate to help judge heat work and even the half dozen or so since then are only somewhat helpful. Erik
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Ivor and Olive Lewis on wed 10 jan 07
Dear Erik Harmon,=20
I am using a Multimeter that gives me a digital scale up to 1300 =
Celsius. The margin of error given by the manufacturer is plus/minus 3 =
per cent of the reading. It is not left permanently in the "On" state. =
It is only activated when to check the progress of a firing. When Cone 8 =
squats the reading, after the unit stabilised, was 1240 Celsius. So the =
temperature inside the sheath at the junction could have been anywhere =
between 1200 and 1280. So I trust the Cones not the pyrometer.
You seem to know a lot about this topic so I ask you, "What are the =
other errors in a pyrometer reading and how can they be nullified? "
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Dave Finkelnburg on wed 10 jan 07
Erik,
Do you use analog pyrometers (the wire is
connected directly to a indication with a swinging
needle) or do you use digital pyrometers (the display
shows numbers)?
My observation is analog pyrometers are cheap to
buy, don't last, and are inaccurate.
My digital pyrometer, on the other hand, has never
failed. A rugged (1/8-inch diameter wire) type K
thermocouple connected to a good-quality digital
display has been good for me. While I readily admit
I'm not firing with salt/soda I don't see any reason
that should do anything except cause a shorter
thermocouple life. Accuracy and reliability should
remain acceptable.
Good potting,
Dave Finkelnburg
--- Erik Harmon wrote:
The first two thermocouples that
> came with the my Skutt seemed to be horribly in
> accurate to help judge heat work and even the half
> dozen or so since then are only somewhat helpful.
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Erik Harmon on thu 11 jan 07
Dear Ivor,
Is a Multimeter the same thing as a pyrometer? Since it is not left in the on state, do you remove the thermocouple between readings or do you just disconnect it. Erik Harmon
Ivor and Olive Lewis wrote:
Dear Erik Harmon,
I am using a Multimeter that gives me a digital scale up to 1300 Celsius. The margin of error given by the manufacturer is plus/minus 3 per cent of the reading. It is not left permanently in the "On" state. It is only activated when to check the progress of a firing. When Cone 8 squats the reading, after the unit stabilised, was 1240 Celsius. So the temperature inside the sheath at the junction could have been anywhere between 1200 and 1280. So I trust the Cones not the pyrometer.
You seem to know a lot about this topic so I ask you, "What are the other errors in a pyrometer reading and how can they be nullified? "
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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Erik Harmon on thu 11 jan 07
Dave,
The first two were analog, since then I have used digital pyrometers. It makes sense to me then, in previous posts that type K thermocouples have been spoken highly about by others in this forum. I dont think I've owned any type K's yet. The Analogs were both used in soda or salt kilns and none of the digital ones had been. I do not want to speak in generalities but none of them were that great. When I have sole decision about the purchase I will definately try a type K. Even though I wonder about the wear of it being used in salt.
What type of pyrometer are you using (brand), and can you tell me roughly whaat it cost?
Erik Harmon
Dave Finkelnburg wrote:
Erik,
Do you use analog pyrometers (the wire is
connected directly to a indication with a swinging
needle) or do you use digital pyrometers (the display
shows numbers)?
My observation is analog pyrometers are cheap to
buy, don't last, and are inaccurate.
My digital pyrometer, on the other hand, has never
failed. A rugged (1/8-inch diameter wire) type K
thermocouple connected to a good-quality digital
display has been good for me. While I readily admit
I'm not firing with salt/soda I don't see any reason
that should do anything except cause a shorter
thermocouple life. Accuracy and reliability should
remain acceptable.
Good potting,
Dave Finkelnburg
--- Erik Harmon wrote:
The first two thermocouples that
> came with the my Skutt seemed to be horribly in
> accurate to help judge heat work and even the half
> dozen or so since then are only somewhat helpful.
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Tired of spam? Yahoo! Mail has the best spam protection around
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Steve Mills on sat 13 jan 07
There are problems with using Pyrometers, Analogue or Digital, normally,
or with either reduction or vapour glazing, or both together.
Pyrometers measure pure temperature as seen at the moment you view them.
They cannot accurately measure accumulated heatwork, and despite various
modifications to replicate that function I doubt they ever will.
Problems associated with using thermocouples in reduction or vapour
firing are to do with the sheath itself. Industrially, Thermocouples
used in those atmospheres are generally double sheathed to reduce or
stop the intrusion of corrosive gasses.
In the context of what the majority of us on this list do this is an
unnecessary complication and expense. Far better to use the Pyrometer
and thermocouple to tell how fast or not we are firing, and use
Pyrometric cones, which DO measure accumulated heatwork, to tell us
where we truly are.
The rules I use are: to go up one cone for wood, up one cone for vapour,
or up two cones for both, and conversely down one cone for reduction.
Steve
Bath
UK
> -----Original Message-----
> From: Dave Finkelnburg [mailto:idahopottery@YAHOO.COM]
> Sent: 10 January 2007 11:41 PM
> Subject: Re: Using a Pyrometer. (Was Yo, Pat Southwood! Cones and
frits)
>
> Erik,
> Do you use analog pyrometers (the wire is
> connected directly to a indication with a swinging
> needle) or do you use digital pyrometers (the display
> shows numbers)?
> My observation is analog pyrometers are cheap to
> buy, don't last, and are inaccurate.
> My digital pyrometer, on the other hand, has never
> failed. A rugged (1/8-inch diameter wire) type K
> thermocouple connected to a good-quality digital
> display has been good for me. While I readily admit
> I'm not firing with salt/soda I don't see any reason
> that should do anything except cause a shorter
> thermocouple life. Accuracy and reliability should
> remain acceptable.
> Good potting,
> Dave Finkelnburg
>
>
> --- Erik Harmon wrote:
> The first two thermocouples that
> > came with the my Skutt seemed to be horribly in
> > accurate to help judge heat work and even the half
> > dozen or so since then are only somewhat helpful.
>
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> Tired of spam? Yahoo! Mail has the best spam protection around
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Lee Love on sun 14 jan 07
Problem with cones, is that they don't tell you when you are loosing
heat (important in a wood kiln.) They only tell you about heat work
over time, in a controlled atmosphere.
A pyrometer and pulling test tiles is a very good combination.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
"When we all do better. We ALL do better." -Paul Wellstone
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