Answer / prashant

in three wire rtd, wire(lead) resistance is compasateed
automatically as per signal cable which is shorted in rtd
probe/sensor.
in two wire rtd we require room temp. compasation. but it
is depend on signal cable length resistance, so we reqire
fix length of signal cable which is lead resistance must
be clculated with room temp. compasation.

Answer / rk

basically as lenght of wire inc resitance inc.henace a lead compensator is given in 3 wire rtd and gives best results over a far distance from source.
but 2 wire rtd has effect of temp.hence it is used for smaller distance which is not much preffered

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