Rockwell Automation 1746-NI16V SLC 500 Analog Input Modules User Manual - Manual (Page 35)

Publication 1746-UM001A-US-P
Installation and Wiring 3-13
Input Devices Transducer Source Impedance
If the source impedance of the input device and associated cabling is
too high, it affects the accuracy of the channel data word. Source
impedance of 2000 ohms produces up to 0.01% of module error over
and above the specified accuracy of the module.
You can compensate for device impedance error by implementing the
following equation in your ladder program:
Wiring Input Devices to the 1746-NI16
After the analog input module is properly installed in the chassis,
follow the wiring procedure below using Belden™ 8761 cable.
ATTENTION
!
Care should be taken to avoid connecting a voltage
source to a channel configured for current input.
Improper module operation or damage to the voltage
source can occur.
V
S
V
measured
(R
s
R
in
)
R
in
where: Vs = input device voltage
Rs = input device impedance
Rin = 1746-NI16 input impedance (See specifications in Appendix A.)
Cable
(Cut foil shield and drain wire.)
Signal Wire
Foil Shield
Drain Wire
Signal Wire
(Twist the drain wire and the foil shield together
and connect to earth ground or to the chassis
mounting screws.)