Red Lion PCU - Manual (Page 41)

Alarm Hysteresis (AHYS)
The alarm(s) values have a programmable hysteresis band to prevent alarm
output chatter near the alarm trigger setpoint. The hysteresis value should be
set to eliminate this effect. A value of 2 to 5 is usually sufficient for most
applications. A single alarm hysteresis value applies to both alarms. See the
Alarm Action Figures, page 30, for the effect of hysteresis on the various
alarm types.
AHYS - 1 to 250
SECONDARY OUTPUT MODULE (5-02) (OPTIONAL)
The optional secondary output (OP2) operates as an independent output for
systems that require a second output. One of the three types of output modules
(Relay, Logic/SSR Drive or Triac) must be ordered separately and installed
into the OP2 channel socket. The output modules may be replaced or
interchanged (with appropriate wiring considerations) at any time without
re-programming the controller.
The front panel indicator OP2 illuminates when the secondary output is on.
(See
Output Module “OUTPUT ON” State Table, page 6, for definition).
Secondary output power is defined as ranging from -100% (full on) to 0%
(off, unless a deadband overlap is used).
Time Proportioning Cycle Time (CYC2)
A value of 0 turns off the secondary output, independent of power demand.
CYC2 - 0 to 250 seconds
Relative Gain (GAN2)
This parameter defines the gain of the secondary band relative to the main
output band. A value of 0.0 places the secondary output into ON/OFF control
mode with the parameter (db-2) becoming the secondary output hysteresis.
This may be done independent of the main output control mode (PID or
ON/OFF). Relative gain is generally set to balance the effects of OP2 to that
of OP1 for best control.
GAN2 - 0.0 to 10.0
Overlap/Deadband (db-2)
This parameter defines the area in which both the main control output and
secondary output are active (negative value) or the deadband area between the
bands (positive value). If an overlap is specified, the displayed percent output
power is the sum of the main power (OP1) and the secondary power (OP2).
db-2 - -999 to 9999
If relative gain is zero, the secondary output operates in the ON/OFF mode,
with this parameter becoming the secondary output hysteresis (positive value
only). The Operation Figures illustrate the effects of different deadbands.
-33-
Figure 18, Operation (db=0)
Figure 19, Operation (db>0)