GE MULTILIN 269 MOTOR MANAGEMENT RELAY Series Instruction Manual page 118

APPENDIX C
Providing the daisy chain is short and RTDs are not Copper, (Copper is very sensitive to extra resistance), the wir-
ing illustrated in fig. 2 should work properly. After the wiring, a quick test of RTD actual values is recommended to
ensure that all six RTDs are reading correctly.
To illustrate this further, let us consider RTD #1. Following the concept demonstrated earlier for finding the RTD
voltage, which will then be translated into temperature, we find that:
V 1,2 = V Lead 1 HOT + V RTD#1 + V Link I + V Link II + V Link III + V Link IV + V Link V + V Lead 6 RETURN
V 2,3 = V Link I + V Link II + V Link III + V Link IV + V Link V + V Lead 6 COMP. + V Lead 6 RETURN
Assuming that the links at the motor side and at the relay side are the same length, gage, and material, therefore
the same resistance, and all the hot, return and compensation leads have also the same resistance, we can con-
clude that:
V 1,2 - V 2,3 = V RTD#1
An illustration of how to compensate a two wire RTD with a run of wire to a central terminal may be seen in figure 3.
NOTE: Wires must all be the same gage, type, and length to ensure that they all have the same resistance, other-
wise additional calculations are required.
C-2