[Cob] How to measure heat inside oven or furnace?

[Amanda Peck]

Ianto mentions using some sort of thermometer in the chimney to see if you 
are going to have to jump through hoops trying to get a draft started (you 
want to be able to compare in-chimney with outdoor temperature).

I'm not sure if he mentions exactly what one is supposed to get for this.  
Something that reads from the mid-thirties up to about 100 degrees (F), but 
won't die in a 300 degree oven?   I guess you could set something in the end 
cleanout. but IIRC the pictures show something mounted in the chimney, where 
you could read it without lying on the floor with a flashlight.

The temperature gauges sold for wood-burning stoves are generally contact 
affairs, you read the temperature of your stove-pipe with this thing that 
stays mounted on it--magnetically would be safest.  That would probably tell 
you hot the top of your heat riser was getting.

People firing ceramics use cones that start to melt at specific 
temperatures.  They also need a window if they want to check things 
real-time, although if you just wanted to know how hot it got the last time 
you cranked it up, and knew about where it was going to be you could just 
leave a couple cones inside it, see what they looked like after it had 
cooled down.  I'm thinking that a window into the oven would be a weak point 
in the oven.

Fairly low-temperature (up to 500--700 degrees F) non-contact pyrometers are 
available at your local automotive speed shop, or the on-line version 
thereof, or BORROWED from your local fairly well set up circle track racer 
in the off season.  You wanted to know why this is a big market? 
Consider--are the tires properly inflated, are the camber of the tires and 
the wedge of the chassis properly set, these things easily checked by seeing 
what the temperatures across the tires is after a handful of laps on the 
track.  They'd work--overkill!--for checking chimney temperature in a heated 
flue bench.  But somewhere around $200 sounds like a little too much to 
spend for something that won't really really do the job on a cob oven. Not 
suitable for continuous duty, and not for remote use either.  The site has 
ones both more and less expensive, by the way, just in case a relative is 
going to need one for racing next summer.

http://www.racerpartswholesale.com/pyrom.htm
.................
Shannon responds to Peter:

On Mon, 1 Nov 2004, Peter Kaulback wrote:

 > I'm almost done my oven and am considering a rocket stove for a
 > livestock area, heat is precious at lambing especially if it's damp :(
 >
 > I've always wondered how one might determine the temperature inside an
 > oven or furnace, is there a special thermometer one can use?

A "pyrometer" (basically a high temperature electronic thermometer) can be
used to measure temperature, no idea what they cost these days.  There are
also some high temperature, optical thermometers (fairly low precision I
believe) I have seen which you aim at the object whose temperature you
wish to measure.  There is also the old fashioned way, a rough temperature
measurement can be acheived by looking at the color of the "glow" from a
hot object, I assume most people have seen steel in person or in
pictures, glowing anywhere from dull red to white, there are temperature
color charts available, and the temperature color scheme as I recall
applies to pretty much any material (though the natural color of the
material may interfere with accurate assessment of the heat color).
Unfortunately, I don't know of any color charts online for temperature
measurement, all the ones I found in a quick search were for image
processing and photography which while related, are not quite the same
thing.

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