Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 36)

Aseembly and Installation
Chapter 2
2Ć23
welders which generate high electrical noise. Equipment grounding can
carry electrical noise when ground loops exists.
The alternate grounding method is for instruments, only. A instrument
ground bus is located inside the enclosure containing the I/O chassis,
manual control station, and PC processor. The instrument bus is
electrically isolated from the I/O chassis and enclosure. The bus is
connected to earth ground by a direct path, independent of other
equipment ground connections.
When using instrument grounding, the only change to the connection
drawings (Figure 2.5 through Figure 2.8 and Figure 2.10) is that the
chassis ground symbol would be redefined as instrument ground. All
cable shields and the +15V dc COMMON terminal of the PID module
would be connected to the instrument ground bus.
When multiple PID modules are placed in the same chassis, the +15V dc
commons and +5V dc commons, if used, should be connected to the
ground bus at one point. Do not daisy-chain the commons.
The PID dual-slot module must be placed with single module group when
placed in a I/O chassis. Up to eight PID modules can be placed in a single
128 I/O chassis. Up to four of the PID modules can be powered from the
+5V I/O chassis power supply. The remaining PID modules, if installed,
must be powered by a separate +5V dc supply through the field wiring
arm +5V dc and 5V dc COMMON terminals. Be sure that the total
current requirement for all modules in the I/O chassis using the I/Ochassis
power supply does not exceed the rating of the I/O chassis and the I/O
chassis power supply.
Avoid placing the PID module close to AC I/O modules or high voltage
DC I/O modules. It cannot be inserted in the left-most slot reserved for the
processor module in a single I/O chassis system or for the I/O adapter
module in a multi-chassis system.
Set switch 1 of the I/O chassis last state switch assembly to the off
position to allow PID module operation in soft fault mode. Refer to
section titled Loop Control Word B for additional information on soft
fault mode selection.
Other intelligent I/O modules can operate without interference in the same
I/O chassis with PID modules.
Chassis Considerations