Maximum RTD Distance

[boardmaker 0]

Just to ask for my own knowledge without doing any research. Does anyone know the maximum wire length between the plc and the rtd. I've been thinking of doing something similar to this, but it's about 400' from the plc.

[Ken Moore 23]

You shouldn't hijack a PID thread with an instrument question. I always use a 4-20mA transmitter for long runs, eliminates a lot of head aches. However, I don't know the maximum distance for a RTD, but the reference leg should take the wire resistance out of the measurement.

[boardmaker 0]

Sorry Ken. I know I shouldn't hijack, but that thread really got my brain going about a possible project.

[TimWilborne 108]

Moved these post out of THIS thread

[DanW 41]

Text below is directly from a Honeywell hybrid controller with universal analog input (TC/RTD/4-20/mV) I would suspect that these numbers vary from input board to input board, depending on mfg. Dan RTD , PT100 3 wire, 40 ohms balanced maximum Thermocouples: 100 Ohms/Leg 100 (except Low), 500 & 1000 RTD: 100 Ohms/Leg 100 YIS: 100 Ohms/Leg 100-Low RTD & 10 ohm Cu: 10 Ohms/Leg