I can buy a lot of type X thermocouples, these are not even very expensive, or I could make some myself.
I can get meters of ISOTAN (Ni 44%, Mn 1%, Cu rest) as resistor wire very cheap. Can I use this in place of constantan? Or does the 1% Mn screw up a type T (copper versus constantan) themocouple? This because wikipedia says nothing about Mn in constantan.
ISOTAN is also 40 uV / K at 20 °C, is this the same?
cheap.
You can use it IF you calibrate each batch (or spool of wire). The small variations allowed for any alloy might cause any unknowable amount of deviation from one melt to another. Some nice thermocouples are Au-Au/Fe, with 0.07% iron doping in the 'Au/Fe' wire. Sometimes it takes only that fraction of percent to make a difference.
Historically, the constantan alloy (Driver trademark?) was a resistance wire, and was available in quantity with known composition. Constantan took to thermocouples well, probably Isotan will, too.
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