Rockwell Automation Publication 1756-UM010C-EN-P - June 2021
119
Appendix
C
Module Schematics
What This Appendix
Contains
Use this appendix to understand the internal logic of the 1756-CFM module.
Follow the wiring practices that are described in your system-level installation
manual when wiring your I/O devices. This includes:
•
Routing conductors
•
Grounding practices
•
use of shielded cables
Input Circuits
The module input logic consists of:
•
Flowmeter input circuits
•
gate input circuits
Flowmeter Inputs
The flowmeter input circuit combines operational amplifier principles with
solid-state devices to provide constant logic pulses internal to the module. The
circuit is designed to interface with both active or passive sensor inputs by
accepting any pulse output device (such as turbine flowmeter, magnetic
pickup or digital pickup).
42845
F0 Return
F1 Return
F1
F0
7
8
10
9
Input
RET
+5V
R116
U21
R117
R118
U22
R119
R120
R121
C70
D32
U23
R123
RV1
D33
R126
S ¥
R125
R29
D34
V
REF
physical and electrical isolation
+5V
C40
F0
F1
U4
C74
TTL level
4V DC level
C76
+5V
