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Amplifying Signal From Type T Thermocouple

Question asked by irisallen on Apr 14, 2016
Latest reply on Apr 18, 2016 by Emman.A

I work in the forestry department at Michigan Sate and I'm looking for some advice on some thermocouples I built. I made them as part of a sap flow measurement system. There are two type-T thermocouples attached by a constantan wire, and they each have their own copper wire coming out (see attached diagram, the copper wires are blue and the constantan wires are red).

I'm trying to hook them up to a data logger (HOBO U12 4-Channel External Data Logger - U12-008 ). Unfortunately, the data logger we're using (we need this kind to work with our other sensors), only takes a 2.5 stereo input and can only detect measurements greater than 0.5V . The output from our thermocuoples will be less than 1mV. I was thinking that maybe to get this to work I could use some sort of amplifier, to increase the signal to a point where the data logger can pick it up.

Also, given that my data logger doesn't seem to do differential voltage, I was thinking of just cutting the wire that connects both data loggers, and measure each thermocouple separately.

Any advice on what sort of amplifier to use, and if this idea works at all?