Gasifier heater mode sensor

I just got a idea of a simple DIY high temp on/off sensor

Its a ss tube with a electrode inside, filled with salt. Salt (NaCl) conducts electriciity only in molten state, and has a melting point of 800C (1470f) wich happens to be around where the gasifier starts overheating. This means when the gasifier enters heater mode, the salt cristals wuld melt and close the circuit.
Allso, different salts culd be used for different temperatures.
What do you think?

Sorry for the bad pic


Would this only be a one-time-use system once those salt crystals melted?
Or would it cool down “reset” for a future usage?

Steve Unruh


It sounds like it will work. but it takes time for the salt to melt, and you are looking at corrosion, and any water in it will start to form NaOH +Cl2 which could affect conductivity and expansion. I would make it a lot smaller, like use a stainless steel coin cell battery case.

The functionality is about the same as a bimetal switch.

You actually might be able to just run a piece of thin welding or ss wire and measure the resistance and have that flip a transistor. The resistance goes up with heat. Along the same lines, you might be able to just attach two wires a fixed distance apart on each side of the gasifier tube itself and measure the resistance since those are metal anyway. It might be too thick to get a measurable reading though. there is a formula and charts for this stuff.

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Steve, the cristals wuld solidify and stop being conductive so yes a multi time use.

Sean, l agree, this might not ba as fast reacting as a thermocouple, but wuld indicate long time overdrawing on the gasifier.

Water at 1500f? Dont think so :wink: allso, the goal is NOT to melt the salt unless something is wrong so 99% of the time it wuld be cristaline.
A electrolisis reaction is possible thugh, making sodium and clorine but in a close vessel they wuld just react back
Yes l agree there are much simpler ways to mesure temp digitaly. But they all require mesuring devices, displays and charts/calculations. Some dont have acces or knowlidge for that. Me being one :smile:


OK, who is going to be the first person to make a prototype and show us a demo? Do you think hooking this up to a 12V LED will work?

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Probbably the person typeing this :smile:

Yes thats what l was thinking. Only thing l need to work out is the plug. Any ideas? It has to withstand heat and not conduct electricity. I thod of pushing the electrode in a fiberglass rope and crimp it in the salt filled tube.


…it isn’t needed at all :stuck_out_tongue:

Actually a stainless steel tube would work better. The glass could shatter from stuff hitting it or thermal shock. So basically like a kitchen temperature probe. You have to isolate the circuit to prevent shorting out…

I think fiberglass will melt at that temp. I was thinking clay but that might conduct unless you dry it, and it shrinks when it dries… but it might work for a quick test when you heat up the end of the tube with the torch. I know you aren’t going to wait long enough for it to dry… lol

Let me give it a try…
I will test it in the oven/reactor i am building,

Imagine a ceramic tube with 2 wires inside, separated by ceramic “blocks”, submerged in salt…

I will test if the salt gets different conductive proportions, if it can work as a switch on/off

It is always fun trying out a friends idea…

Meanwhile enjoy reading:

edit: found clip on youtube


Great Koen! Keep us posted.

Ha, the last video is preety much what l had on mind.


Hi Cris:
Nice to hear from you!
This idea looks like a simple and brillant !! It need to be tested. Also other materials may be good for other range of temperatures. We may need a chemistry here to give us some feedback.
Eddy Ramos.


Could you not just make the salt capule longer, so that the open end extends outside of the hot zone? Then the material to seal it may be less of an issue. It’s true the molten salt would eventually tranfer the heat out there, but perhaps something could be placed in the cold end to physically prevent the salt from reaching that end.


$6 on ebay from China
Will this react with salt?

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