User guide

2–8 Installing the Input Module
    
Connect your I/O devices to the cat. no. 1771-WG wiring arm
shipped with the module. The wiring arm is attached to the pivot bar
at the bottom of the I/O chassis. It pivots upward and connects with
the module so you can install or remove the module without
disconnecting the wires.
!
ATTENTION: Remove power from the 1771 I/O
chassis backplane and field wiring arm before
removing or installing an I/O module.
• Failure to remove power from the backplane or wir-
ing arm could cause module damage, degradation of
performance, or injury.
• Failure to remove power from the backplane could
cause injury or equipment damage due to possible
unexpected operation.
Input connections for the 1771-IFE module with single-ended inputs
are shown in Figure 2.1 and Figure 2.2. Input connections for the
1771-IFE with differential inputs are shown in Figure 2.3 and
Figure 2.4.
Minimizing Ground Loops
To minimize ground-loop currents on input circuits:
• use single-ended mode whenever possible
• use 2-wire transmitters with a common power supply
• separate 2-wire and 4-wire transmitters between different
modules
• tie 4-wire transmitter and/or separate power supply grounds
together
Important: We do not recommend mixing 2-wire and 4-wire
transmitter inputs on the same module. Power supply
placement can make it impossible to eliminate ground
loops.
Cable Lengths
Recommended maximum cable length for voltage-mode input
devices is 50 feet. This recommendation is based on considerations
of signal degradation and electrical noise immunity in typical
industrial environments. Cable length for current-mode input
devices need not be as restrictive because analog signals from these
devices are less sensitive to electrical noise interference.
Wiring Your Analog
Input Module