Thermocouples are two wire units composed from dissimilar metal welded with each other which when warmed up generate a tiny millivolt probable. The result depends upon the type of material of development by using a total array of different components for varying apps and temperatures varieties, that is way past the scale on this write-up. Such as a general low cost thermocouple would be a type K which can be manufactured from Nickel and Chromium and produces an output of 41µV/oC being a magnet substance might cause some difficulties with linearity at temps over 350ºC this is once more away from scope with this report. For greater heat apps Kind B, R or S works extremely well up to 1600ºC these thermocouples are considerably more pricey simply being constructed from Platinum / Rhodium by having an output of 10µVºC.
The problem with thermocouples is because they can not be connected to standard copper cord as an additional junction of different alloys would be produced in the hooking up go which will also produce a millivolt indicate so therefore a mistake. So a cable tv with the same qualities as the thermocouple should be used for connecting returning to the custom thermocouples this is known as compensating cable. The connection in the musical instrument terminals using the comp cable television can make a small millivolt possible which should be compensated just for this is sometimes called the frosty junction temperature.
The temperature tool or transmitter items a minimal voltage towards the platinum opposition indicator which in turn causes a current to circulate; generating an electrical circuit.
By ohms law the voltage drop inside the circuit so therefore the current movement is proportional to the amount of resistance within the circuit. Because the temperatures raises the amount of resistance in the PT100 improves:- this really is a positive thr0k coefficient. The issue together with the two wire design may be the musical instrument reads the level of resistance from the linking cable tv plus the heat detector.
There are many methods to circumnavigate this issue has listed here within the link particulars for your 3 And 4 wire systems.