Answer / carl_ellis

The RTD element is ALWAYS isolated from the sheath. Dual
element RTDs should be isolated from each other.
Therefore, there should be no common electrical connection
between any wire in a dual element RTD.

The fact that a connection to one receiver (the PLC)
disturbs the other receiver's RTD reading means either

a) the RTD elements or lead wires are shorting to either
the sheath, the other RTD element or a lead wire; meaning
the RTD assembly is damaged internally.

b) the field wiring for one RTD is shorting to the field
wiring of the other RTD

Carl Ellis
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