Watlow ez-zone pm - Timer Function and Alarms

Watlow EZ-ZONE
®
PMI Controller • 196 • Chapter 9 Features
Proportional, Integral and Derivative (PID) Control
Use derivative (rate) control to minimize the overshoot in a PI-controlled system. Derivative
(rate) adjusts the output based on the rate of change in the temperature or process value.
Too much derivative (rate) will make the system sluggish. Adjust the derivative with Time
Derivative td (Operations Page, Loop Menu).
Dead Band
In a PID application the dead bands above and below the set point can save an application’s
energy and wear by maintaining process temperature within acceptable ranges.
Proportional action ceases when the process value is within the dead band. Integral action
continues to bring the process temperature to the set point. Using a positive dead band
value keeps the two systems from ghting each other.
When the dead band value is zero, the heating output activates when the temperature
drops below the set point, and the cooling output switches on when the temperature ex-
ceeds the set point.
Time
Temperature
PID Control
Set Point
Reduced Overshoot
Proportional Band
Time
Temperature
Positive Dead Band
Set Point
Heat Output Active
Cool Output Active
Time
Temperature
Zero Dead Band
Set Point
Heat Output Active
Cool Output Active