Rockwell Automation 1760-xxxx Pico Controller User Manual - Manual (Page 43)

Publication 1760-UM001D-EN-P - September 2005
Installation 2-19
Connect Analog Inputs (1760-LxxBWB-xx or 1760-LxxDWD only)
Inputs I7 and I8, and if present I11 and I12, can also be used to
connect analog devices ranging from 0 to 10V dc.
Use shielded, twisted-pair cables to prevent interference with the
analog signals. For short cable lengths, ground the shield at both ends
with a large contact area. If the cable length exceeds 30m (98.4 ft),
grounding at both ends can result in ground loops between the two
grounding points and thus to the interference of analog signals. In this
case, only ground the cable at one end. Do not route signal lines
parallel to power cables.
Connect inductive loads to be switched via Pico outputs to a separate
power feed, or use a suppressor circuit for motors and valves. If loads
such as motors, solenoid valves or contactors are operated via the
same power feed, switching may result in interference on the analog
input signals.
ATTENTION
Analog signals are more sensitive to interference than
digital signals. Consequently, more care must be
taken when routing and connecting the signal lines.
Route the analog wiring:
• away from power lines, load lines and other
sources of electrical noise such as hard-contact
switches, relays, and AC motor drives
• away from sources of radiated heat
Incorrect switching states may occur if the analog
wiring is not installed correctly.