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I am building a temperature monitoring system that has 24 thermocouples. Managing all the wires is a hassle, and I'd like to connect all 48 wires to a few plug and socket connectors. Maybe 6 of these lead wire harnesses from eBay (see below).

The point of this would be to allow me to quickly disconnect all the thermocouples from their amplifiers when I need reposition the arduino, and then reconnect them afterwards without tracking each individual cable.

I don't know if this will have a negative impact on the function of the thermocouples. Is it ok to have a 'joint' (i.e., the socket) in the thermocouple cables, or do they need to remain intact from the end all the way to the amplifier?

Alternatively, would having a few inches of regular copper wire inserted between the thermocouple wires and the amplifier be ok? That is, having two copper wires attached to the amplifier, joining 8 of these wires together in a socket, and attaching the plug to the actual thermocouple (alumel/chromel) wires? The thermocouple wires are several feet long.

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I do not know the accuracy that you will require in your temperature measurements.

Your idea of using copper wire and connector sockets is reasonably ok as long as you are aware of the following :

Where you make a connection from thermocouple wire to copper, that creates another thermocouple in itself. This isn't a great problem since the temperature of the "undesired" thermocouple is likely to be at room temperature (constant?)

No matter what you do, you always end up with undesired thermocouples (example when you connect your thermocouple directly to your circuit board copper, darn it.)

Thermocouple Selection and use is a page you can go to for more information. Especially the Cold junction compensation (CJC) section.

EDIT added : You should twist your extention leads together to reduce electrical noise from the environment. Twist each pair, do not twist the bundle all together.

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  • Thanks Marla! The whole setup is in a greenhouse, and the temperature of the thermocouples (desired and undesired) will fluctuate from 0C (hopefully not lower, but it is -20C outside tonight) to +35C. I'll study the page you linked, it looks like exactly the info I needed.
    – Tyler
    Jan 5, 2016 at 3:21
  • On the linked page, the author uses words like "must use", strong language encouraging to use thermocouple wire for extensions. But that merely reduces the number of unintended thermocouples.
    – Marla
    Jan 5, 2016 at 3:24
  • I'd put the sockets upstream of the amplifiers, ie arduino---sockets---amps---TCs Jan 5, 2016 at 20:18

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