Allen-Bradley FLEX I/O 1794-IJ2, Руководство пользователя, Страница: 72 / 80

Publication 1794-6.5.11 - November 1997
Appendix
B
Schematics
What This Appendix
Contains
Use this appendix to understand the internal logic of the 1794-IJ2 module.
Input Circuits
The frequency input module input logic consists of:
• frequency input circuits
• gate input circuits
Frequency Inputs
The frequency input circuit uses a comparator to determine when the
input voltage threshold is exceeded. When exceeded, it provides logic
pulses internal to the IJ2 module. The circuit is designed to interface with
both active or passive sensor inputs by accepting any pulse output device
(such as vortex flowmeter, magnetic pickup or digital pickup).
Gate Inputs
Gate inputs are similar to frequency inputs and are used for determining
direction. There is one gate associated with each frequency input circuit
(G0 corresponds to F0). The circuit is designed to interface with both
active or passive sensor inputs by accepting any pulse output device (such
as magnetic pickup or digital pickup).
Follow the wiring practices described in “Industrial Automation Wiring
and Grounding Guidelines for Noise Immunity,” publication 1770-4.1,
when wiring your I/O devices. This includes:
• routing conductors
• grounding practices
• use of shielded cables