pyrometer, are they acurate?

i don't know that brand, is it a digital or needle indicator? needles can stick, but digitals should not "stick" and get loose to read a hundred dregees more all of a sudden from a tap.

a build in pyrometer - i would think - would read very well as being part of the overall product design.

my 1st impression of your question was that pyrometers read exactly right - only right where the pyrometer tip is. elsewhere in the kiln the temp is different.

i use my pyrometer as a guide to know the kiln temp is rising or cooling after various flew adjustments. sometimes flew adjustments can snuff out the flames and cool off the kiln (reduction) when i think it should be rising. (i might not realize the flew postion is still forcing reduction). for me i use my analog pyrometer for indication purposes only. and i know my pyrometer location is low by some 200°F. (i'm still tweaking my kiln - the door needs a better seal).

also, i've come to use color in the kiln as a guide until the color is hotter then the low dim red. really hot color in the kiln can & will burn your retinas out. i suppose this can happen even at the low dim red but i take that risk along with a cold beer & hot pizza...

see ya

steve

steve graber

Thanks Steve Yeah, it's a built in needle type. It's new to me, as I had a little electric kiln years ago, and I always went by the color. Then, I knew nothing about candeling, or slow warm ups, or nothing. I just turned it on, turned it off when I thought it was done. Funny thing, I had no trouble at all. This is a big ol' gas job, and I know there is much tinkering, and I am still figuring it out. I have done 2 bisque firings, neither did I reach 05, as far as I can tell. If the pyrometer was accurate, I know I didn't. I also had a kiln sitter cone in place the last time, but still shut the kiln off before it did, as I had been firing for 14 hours, and had to go to bed. It was all glowy, and I just relied on what I had done in the past. Everything came out fine, with the exception of some cracks in a couple pieces.

I was hoping to avoid these things by doing a slow warm up, but as the pyrometer was so wonky, I had a real hard time telling if I had held it at 200 degrees, or had it jumped to 800.

I guess that's the main problem, and I know experience is the best teacher. Picking other folks brains is good too. Thanks again Sea Ya Sa Námarië

If it's a new kiln and the needle changes that much from tapping, I'd talk to the manufacturer. Some people put up with that kind of sticky-needle stuff on an old meter, but if a new one is sticking I'd worry that there is mechanical damage.

As far as accuracy, I don't know about your setup, but I wouldn't expect to get anything outstanding when the whole works is mounted on the kiln. (Poor control over the reference junction temperature.) By this I mean that you may not be able to match the cone-drop numbers on the Orton chart or whatever. However, you should get good repeatability from one firing to the next, and that's probably all you need, once you have a rough idea about what reading corresponds to what cone at what firing rate, etc. And you should be able to get decent relative readings for things like "cool 200 degrees and hold for X minutes".

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

The problem with pyrometers is that they only read the temperature as it is the millisecond that you look at it, they don't read accumulated heatwork which is what cones large and small do. Only if you fire at

150 degrees C per hour will they both agree, and that's only because the *temperature* value of a cone is based on that rate of heat rise. If your Kiln Sitter did not drop before the controller shut it all down, then the Pyrometer is reading seriously fast and needs re-calibrating. Both at home and at work I/we use a controller to run the firing, and a Kiln Sitter to shut it off at the right moment, to this end we always program the controller at least 50 degrees C more than the end point wanted, and we check the pyrometer regularly for accuracy. Cones are reliable because they respond to heatwork in the same way as clays and glazes.

Steve Bath UK

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