Limit Monitoring and Local Real-Time Control
Shown in the diagram below, there are two DUAL-LIMIT DISPLAYS immediately above the bargraph—one to indicate upper and lower "CAUTION" zones (yellow), and other to indicate upper and lower "DANGER" zones (red).
Along with the bargraph, these displays let the operator see immediately which of seven distinct limit zones the current data reading occupies (there are six "VIOLATION" zones and one "SAFETY" zone). Any one limit violation or logical combination of multiple violations can be made to trigger an isolated TTL-level logic control output or the automatic execution of one of more 4000 Series mnemonic commands—including flashing of the digital display.
In the "standard configuration" of each "standard input" model, some or all of the unit's eight negative-true TTL-level LOGIC I/O PORTS (shown in the rear-panel diagrams below) are initially dedicated to specific limit-triggered control outputs. As such, they can be used to actuate solenoid valves, illuminate panel displays, sound alarms, start and stop motors or pumps, initiate and control safety shut-down sequences, and perform many other automation tasks that require "intelligent" switching, even of substantial amounts of power.
Logic I/O ports can be easily reprogrammed, if desired, for a number of useful input functions, such as "reset max/min," "auto zero," "lock data," and "print enable."
Every user-specified limit value may be either fixed (constant-valued) or continuously equal to the current reading of another data channel. The latter feature allows continuous comparison of individual channels.
A user-scalable ±10 VDC ANALOG OUTPUT is generated for strip-chart recording, input to other systems, or general-purpose signal monitoring. The analog output can also be used as feedback for a PID control loop.