Any thoughts about how to sense temperatures up to 1400 C inside a kiln, for purposes of logging the data or feedback to the microprocessor that controls it?
- posted
16 years ago
Temperature sensing
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- posted
16 years ago
Thermocouple. Type S or R in an alumina protection tube if you want long life and good performance.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
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- posted
16 years ago
Alumina (sapphire-like) melts around 2000C or so, though I think I'd only safely consider it usable to 1700C. The OP might refer to:
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to see what your suggestion looks like and get an idea as to pricing.
I don't know what the thermal response time of a kiln looks like, but I suppose it's on the order of minutes. I'd guess the response time of this kind of assembly should be fine with PI or PID. Positioning might be important.
Offhand, Spehro, it would seem to me that the finer gauge thermocouple is better, because it will respond faster. But do you know why someone might choose the heavier gauges? [They cost a LOT more (platinum isn't cheap.)]
Jon
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- posted
16 years ago
Buy a thermocouple (Platinum/Rhodium from memory) designed for the purpose ? These have a low mV output (12-16mV IIRC), that is slightly non-linear so nothing too complex. Needs a precision amplifier, and a correction table, if you want an accurate display over the whole range.
-jg
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- posted
16 years ago
As he only needs to go to 1400°C that would seem to be sufficient. There are cheaper ceramics for lower temperatures that might be marginal at 1300-1400°C.
In this case, response time will be limited by the thick and heavy protection tube, but yes that's true. At least the extra pole will probably not be significant from a control pov.
There are some metallurgical effects, IIRC, depending on the atmosphere the metal is exposed to, but typically I think AWG30 is okay for a situation like this for moderately heavy use. Stuff diffuses in and out and the alloy diffuses across the junction to some extent at those temperatures. You might want a heavier gauge if it's a big industrial installation. There is no significant electrical difference, of course. The Pt is recycled.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
- Vote on answer
- posted
16 years ago
Don't re-invent the wheel - my company has already done this. We can supply you with an S-Type thermocouple designed specifically for use in a kiln and is good for up to 1600C. Check out
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or e-mail me and I'll put you in touch with our sales chaps.
It is designed for use with our exhaust gas analyser but you could easily use it with your own circuitry - you just need to be able to measure from about 0 to 17mV. Bear in mind that 0V is not zero degrees.