Karen Sullivan on wed 11 jul 01
Has anyone heard of an optical pyrometer?
I am curious how one would use it...I have always
thought that the real temperature in the kiln...
i.e. the temperature measured by a pyrometer
is actually lower than the heat work temperature
measured by a pyrometric cones.
So a hypothetical question....
If cone 10 is down, is the actual temperature
2381 degrees F....or a lower temp. and what temp
would the optical pyrometer measure?????
I guess I am asking how one would use such a device.
And does anyone know where one would locate such a toy?
many thanks,
bamboo karen
Malcolm Cooke on thu 12 jul 01
on 12/7/2001 4:30 PM, Karen Sullivan at kwinnies@EARTHLINK.NET wrote:
> Has anyone heard of an optical pyrometer?
> I am curious how one would use it...I have always
> thought that the real temperature in the kiln...
> i.e. the temperature measured by a pyrometer
> is actually lower than the heat work temperature
> measured by a pyrometric cones.
>
> So a hypothetical question....
> If cone 10 is down, is the actual temperature
> 2381 degrees F....or a lower temp. and what temp
> would the optical pyrometer measure?????
>
> I guess I am asking how one would use such a device.
> And does anyone know where one would locate such a toy?
>
> many thanks,
> bamboo karen
>
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Hi All
Optical pyros are no toy and are expensive. They work by reading the surface
tempt ure of what you are looking at in the kiln. They have an element which
is heated in the view finder the calibrated control you turn until the
colour matches the surface of the target and then read off the tem off the
scale on the outside. Very accurate instruments.
--
Regards
Mal Cooke
mcooke@asiaonline.net.au
The Art Shed
Pottery Studio and Gallery
Tharwa ACT 2620
Australia
Marianne Lombardo on thu 12 jul 01
I am currently reading a wonderful book full of tidbits of information. It
was published in 1973 and written by Robert Fourner, called "Illustrated
Dictionary of Practical Pottery". There is a photo of an optical pyrometer,
as well as a description.
Those uninterested need read no further. This is what the description says.
"Commonly the disappearing filament type, where the temperature is measured
by the comparison of two light sources: firstly the light from a lamp
filament which is adjustable and secondly the light radiated through the
kiln spyhole. Both are viewed through a red filter which renders them
monochromatic. The system takes advantage of the fact that the intensity of
light at any one wavelength depends on the temperature of the 'hot body'.
The brightness of the filament is adjusted until it matches that of the kiln
when it will apparently disappear. The setting on a connected ammeter reads
on a scale as a temperature. The device needs recalibrating at intervals.
If your kiln has a small spyhole some sort of stand or tripod is essential.
It has been found to produce somewhat subjective results. Using an optical
pyrometer the hot interior of the kiln is sighted and focussed through the
spyhole. The knob on the side is then turned until the glowing filament
inside the pyrometer disappears. The temperature can be read on the dial
below the eye-piece."
Marianne Lombardo
Omemee, Ontario, Canada
email: mlombardo@nexicom.net
----- Original Message -----
From: "Karen Sullivan"
> Has anyone heard of an optical pyrometer?
Richard Aerni on thu 12 jul 01
I was given an optical pyrometer some years ago by a scientist who no longer
had need of it. It is a kind of meter whereby one can look into the sun, or
a nuclear blast, or a bright source of heat, such as the kiln, and by
calibrating the light emitted with an optical scale in the device, measure
accurately a high temperature. It is a fairly cumbersome device, and
training it to look into the spyhole of the kiln was difficult. I use a
digital pyrometer and pyrometric cones instead. I keep the optical
pyrometer around as a kind of novelty device.
I would guess a scientific supply store would be the place to go.
Hope this helps,
Richard Aerni
Bloomfield, NY
----- Original Message -----
> > Has anyone heard of an optical pyrometer?
> > I am curious how one would use it...I have always
> > thought that the real temperature in the kiln...
> > i.e. the temperature measured by a pyrometer
> > is actually lower than the heat work temperature
> > measured by a pyrometric cones.
> >
> > I guess I am asking how one would use such a device.
> > And does anyone know where one would locate such a toy?
Snail Scott on thu 12 jul 01
At 11:30 PM 7/11/01 -0700, you wrote:
>Has anyone heard of an optical pyrometer?
Yes; all the technogeeks that surround me regard
them as something hardly more exotic than an
electric can opener. Don't know offhand where to
get one, but they're not rare.
>If cone 10 is down, is the actual temperature
>2381 degrees F....or a lower temp. and what
>temp would the optical pyrometer measure?
The temperature given as the 'equivalent' of
^10 (or any other) is based on an assumption
about how fast you are firing. If you fire
faster, you will hit that temperature before
you do the heat-work equivalent to ^10; you
may only reach ^9 or lower. If you fire slower,
you will reach ^10 at a lower temperature.
The pyrometer may read 50 F lower, but it will
still be a ^10 amount of heat-work. Time can
be subtituted for temperature (within limits).
Any pyrometer, optical or otherwise, can only
tell you the temperature. That's where all those
charts in the back of books become useful - to
allow you to guess, based on the rate of
temperature increase, what cone (amount of heat-
work) you have actually achieved.
Pyrometers may look techy and accurate, and they
are, within their limitations. They just don't
give us all the information we need. Plain ol'
pyrometric cones (molded chunks of dirt) do.
Where pyrometers become most useful is in trying
to hold a level temperature (soak), or monitor
the rate of cooling, neither of which is
achievable with cones.
-Snail
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