Heat Only ON-OFF Control : Select REVR for OUT1, Set PB to 0,
O1HY is used to adjust dead band for ON-OFF control, The output 1
hysteresis ( O1HY ) is enabled in case of PB = 0 . The heat only
on-off control function is shown in the following diagram :
SP1
SP1 O1HY
ON
OFF
OUT1 Action
PV
Dead band = O1HY
Time
Time
Figure 3.2 Heat Only
ON-OFF Control
The ON-OFF control may introduce excessive process oscillation even
if hysteresis is minimized to the smallest. If ON-OFF control is set ( ie.
PB = 0 ), TI, TD, CYC1, OFST, CYC2, CPB, DB will be hidden and have
no function to the system. The auto-tuning mode and bumpless
transfer will be disabled too.
Heat only P ( or PD ) control : Select REVR for OUT1, set TI to 0,
OFST is used to adjust the control offset ( manual reset ). O1HY is
hidden if PB is not equal to 0. OFST Function : OFST is measured by
% with range 0 - 100.0 %. In the steady state ( ie. process has been
stabilized ) if the process value is lower than the set point a definite
value, say 5 LC, while 20 LC is used for PB, that is lower 25 %,
33
