Red Lion PCU - Manual (Page 70)

ON/OFF CONTROL
The controller operates in the ON/OFF
control mode by setting the proportional
band = 0.0%. The ON/OFF control hysteresis
band (CHYS) parameter eliminates output
chatter around setpoint. The Secondary output
can also be used in the ON/OFF control by
s e t t i n g t h e r e l a t i v e g a i n = 0 . 0 ( G A N 2 ) .
Additionally, the deadband parameter (db-2)
determines the amount of operational deadband
or overlap between the two outputs.
The phase of the control action can be
reversed by the output control action parameter.
ON/OFF control is usually characterized by
signal oscillations about the setpoint value.
Large hysteresis values make the oscillations
larger. ON/OFF control should only be used
where the constant oscillations are acceptable.
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Figure 33, OP1 On/Off Action Figure 34, OP2 On/Off Action