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What type of thermocouple is used in JBC irons ? (Maybe type N)

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whatsthegeek:
Hi, I'm trying to design my own controller for a JCB series 245 iron (I know there's a project on dangerous prototypes that does it but I's quit complex and I won't learn anything by just using it ^^). I want to use an all-in-one chip but I need to know what type of thermocouple is used :/

Some people says it's a type K and others say it's not, so it's quit confusing...

Maybe if one of you guys have one and have a bit of free time, you could heat up the tip to 200° and measure the voltage drop between the metal body and the last contact,
It could tell me exactly what type of thermocouple is used.

Thanks in advance !  :)

wraper:
If you have a cartridge, you can easily measure it yourself. Type K is a most common thermocouple type and it is well suitable for such task. Say put it into boiling water compare measured voltage with a chart. Or if you have  multimeter with thermocouple function, you could connect it and see if measured value is matching.

whatsthegeek:
I don't have the cartridge yet :/ I want to be sure I can easily make a circuit to control it before buying it, It's super expensive...

That's why I'm asking here, otherwise, I would be already done  ;D

AndyC_772:
OK, I've tried a very simple and not very scientific experiment:

- fit a cartridge into the handpiece and set to 200C
- apply a blob of solder, which does just about melt, to aid thermal conductivity
- place the tip of a second cartridge (C245-907, for what it's worth) against the tip of the first cartridge
- connect DVM probes between the body of the second cartridge and the contact right at the end
- wait a couple of minutes and watch the voltage increase

Final result was about 4.14mV. It takes much longer to reach anything like a steady state than I would have expected.

whatsthegeek:
Ok, thank you sooo much ! Comparing it to the chart, the closest thermocouple type is a type N

On a type N, 4.14mV corresponds to 144°C. Since the conctack between the cartridges wasn't perfect, it looks like it matches pretty well !

I don't know why they would use a type N instead of a type K though ? Maybe because it has a longer life span ?

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