Watlow MICRODIN - Manual (Page 39)

Control Methods
On/Off Control
On/off control switches the output either full on or full off, depending on the
input, set point and hysteresis values. The hysteresis value creates a buffer zone
that increases the time interval that the output is off or on. With hysteresis set
to 0 the process value would stay closer to the set point, but the output would
switch on and off more frequently, causing “chattering.”
Set hysteresis with Output Hysteresis (PID Group).
Figure 4.7 — On/Off Control for Heating and Cooling
Wa t l o w M i c r o D I N 4 . 7
Features
Hysteresis
Time
Temperature
Cooling Action switches
on at Startup
Process Temperature
Cooling Action Switches on when the
Process Temperature rises above the
Set Point plus the Hysteresis
Cooling Action Switches off when the Process Temperature
drops below the Set Point
Set Point
Set Point
Time
Temperature
Heating Action switches off when the Process Temperature
rises above the Set Point
Heating Action switches
on at Startup
Hysteresis
Process Temperature
Heating Action switches on when the Process Temperature
drops below the Set Point minus the Hysteresis