Rockwell Automation 1760-xxxx Pico GFX-70 Controllers User Manual - Manual (Page 59)

Publication 1760-UM002B-EN-P - March 2005
Installation 2-25
Connecting Analog Inputs
Inputs I7, I8, I11 and I12 can also be used to connect analog voltages ranging
from 0V dc to 10V dc.
The following applies:
• I7 = IA01
• I8 = IA02
• I11 = IA03
• I12 = IA04
The resolution is 10-bit = 0 to 1023.
• Use shielded twisted pair cables to prevent interference with the analog
signals.
• For short cable lengths, ground the shield at both ends using a large
contact area. If the cable length exceeds 30m or so, grounding at both
ends can result in equalization currents between the two grounding
points and thus in the interference of analog signals. In this case, only
ground the cable at one end.
• Do not lay signal lines parallel to power cables.
• Connect inductive loads to be switched via the Pico GFX-70 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 with
Pico GFX-70 via the same power feed, switching may give rise to
interference on the analog input signals.
The following circuits contain examples of applications for analog value
processing.
ATTENTION
Analog signals are more sensitive to interference than
digital signals. Consequently, more care must be taken
when laying and connecting the signal lines. Incorrect
switching states may occur if they are not connected
correctly.
IMPORTANT
Ensure that the reference potential is connected. Connect
the 0V of the power supply unit for the different set point
potentiometers and sensors shown in the examples to the
0V terminal of the Pico GFX-70 power feed.