Rockwell Automation 900-TC32 Digital Temperature Controllers, Series B - Manual (Page 96)

Publication 900-UM007D-EN-E - January 2011
3-26 Configuration & Basic Operation
The default is
onof.
Hysteresis
In the ON/OFF control method, hysteresis is used to provide a
margin/differential for switching the control output ON when the controlled
temperature moves away from the required set point. The Hysteresis
parameter is used to give stability to the output around the set point.
The hysteresis value for HEAT control output and COOL control output
functions are configured in the Hysteresis (HEAT) and Hysteresis (COOL)
parameter functions respectively. In standard heating or cooling control, the
HEAT Hysteresis setting is used as the hysteresis setting (Adjustment function
group) regardless of the control mode, heating control or cooling control.
Figure 3.43 — Reverse Operation
3-Position Control
In the heating and cooling control method, a dead band (an area where both
control outputs are 0) can be configured for either the heating or cooling side
of the set point. This makes 3-position control possible.
Figure 3.44 — Reverse Operation with 3-Position Control
Set point
Heat Hysteresis
ON
OFF PV
Set point
Hysteresis (OUT1)
Heating
side
Dead band
Hysteresis (OUT2)
Cooling
side
ON
OFF PV