User`s manual

80 Chapter 7 535 User's Manual
Applications
Figure 7.8
Duplex with One ON/OFF Output
PID OUTPUT
100%
PARAMETER SETTINGS
ACTION:1 = REVERSE
ACTION:2 = DIRECT
PID OFST.:1 = 0
ON OFST.:2 = + VALUE
LOW OUT = 0
HIGH OUT = 100
ON
50%
100%
0%
Out 1
(Heat)
Out 2
(Cool)
Out 1
OFF
0%
Out 2
Out 2 Offset
from Setpoint
in Engineering Units
Figure 7.9
Duplex with Two ON/OFF Outputs
PROCESS VARIABLE
ON
PARAMETER SETTINGS
ACTION:1 = REVERSE
ACTION:2 = DIRECT
ON OFST.:1 = – VALUE
ON OFST.:2 = + VALUE
ON
SP
High
Range
Out 1
(Heat)
Out 2
(Cool)
Out 1
OFF
OFF
Out 2
Offset 2
Low
Range
Offset 1
Notice that the relative gain setting does not affect output 1. In this example, a
relative gain setting of 2.0 (curve 1) results in output 2 reaching its maximum
value at a PID output of 25%. A relative gain setting of 1.0 results in output 2
reaching its maximum value at a PID output of 0%. A relative gain setting of 0.5
results in output 2 reaching a maximum of 50% at a PID output of 0%.
Duplex with one ON/OFF output
A reverse acting output 1 and a direct acting, on/off output 2 with a positive offset.
Relative gain does not apply when using duplex with an on/off output. The
deadband setting for output 2 works the same as the deadband in single on/off
control (the deadband effect for output 2 is not illustrated here).
Duplex with two ON/OFF outputs
A reverse acting on/off output 1 and a direct acting on/off output 2 with a negative
offset for output 1 and a positive offset for output 2.
Note that here the horizontal axis is expressed in terms of process variable
rather than PID output.