Checking for common mode voltages, Affect of common mode voltage on inputs, Use single-ended mode – Rockwell Automation 1771-IFE ANALOG INPUT MODULE User Manual
Page 57: Use 2-wire transmitters with a common power supply, 7–7 troubleshooting your input module
7–7
Troubleshooting Your Input Module
Publication 1771Ć6.5.115 - February 1999
Common mode voltage on any input must not exceed +14.25V as
referenced to module common (terminals 20 and 21). Common mode
voltages occur when the ground potentials of current transmitter
and/or voltage device power sources are at differential potentials (as
referenced to module common). The resulting ground currents can
cause voltage potentials at the input terminals.
Observe the following guidelines whenever possible to prevent
common mode voltages:
•
use single-ended mode
•
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
Affect of Common Mode Voltage on Inputs
If common mode voltage exceeds +14.25V on any input, channel to
channel crosstalk can occur. All channel input data in the
programmable controller data table could be invalid. Incorrect
overrange and underrange bits could also occur
Data Table Report
PLCĆ5/11
Addr 4 IFE
Data Table File N7:0
ADDRESS
N7:10
N7:0
N7:30
N7:20
0
0
0
0
0
0 16533
0 16533
0
0
1
2
3
4
5
6
7
8
9
N7:50
N7:40
N7:70
N7:60
N7:90
N7:80
N7:100
16533
0 16533
0 16533
0 16533
0 16533
0
16533
0 16533
0 16533
0 16533
0 16533
0
16533
0 16533
0 16533
0 16533
0
0
0
2
-1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Data Table Report
PLCĆ5/11
Addr 4 IFE
Data Table File N7:0
ADDRESS
N7:10
N7:0
N7:30
N7:20
0
0
0
0
0
0 16533
0 16533
0
0
1
2
3
4
5
6
7
8
9
N7:50
N7:40
N7:70
N7:60
N7:90
N7:80
N7:100
16533
0 16533
0 16533
0 16533
0 16533
0
16533
0 16533
0 16533
0 16533
0 16533
0
16533
0 16533
0 16533
0 16533
0
0
0
2
-2
1
0 16533
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Data Table Report
PLCĆ5/11
Addr 4 IFE
Data Table File N7:0
ADDRESS
N7:10
N7:0
N7:30
N7:20
0
0
0
0
0
0 16533
0 16533
0
0
1
2
3
4
5
6
7
8
9
N7:50
N7:40
N7:70
N7:60
N7:90
N7:80
N7:100
16533
0 16533
0 16533
0 16533
0 16533
0
16533
0 16533
0 16533
0 16533
0 16533
0
16533
0 16533
0 16533
0 16533
0
0
0
2 -21846
1
0 16533
0
5950
0
5950
0
5950
0
5950
0
5950
0
5950
0
5950
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Block transfer read with channel 1 input <14.25V
and all channels connected to module common
Normal block transfer read with all
channels connected to module common
Block transfer read with channel 1 input approximately 20V
and all channels connected to common
Checking for Common
Mode Voltages