Two-range P controllers
The two-range P controller is the preferred
choice for neutralisation in batch processes.
In accordance with the processbased titration
curve, the control amplification can be set for
an inner and an outer pH/redox range.
Parameter setting of the controller is via the
values G
inner range
, G
outer range
, X
o
and X
u
.
Note:
Positive output values activate
control contact 1, negative output
values activate control contact 2 on
all controllers. The allocation
contact/control function has to be
set in chp. 7.1.3, »relays allocation«.
Actuating signal outputs
The control contact in question issues a
cycled signal, the intensity of which
corresponds to the controller output value.
According to the nature of the signal cycle,
a distinction is made between:
•
Pulse-length modulation: The length of time
the contact concerned remains closed
increases as the size of the calculated
deviation increases. The period can be
set between 0.5 and 99.9 s. Pulse-length-
modulated outputs are used to activate
solenoid valves.
•
Pulse-frequency modulation: The switching
frequency of the contact concerned
increases as the size of the calculated
deviation increases. The maximum
switching frequency of 1/T can be set
between 60 and 180 1/min. The switching
time t
ON
is constant. Pulse-frequency-
modulated outputs are used to activate
solenoid metering pumps.
on
on
off
off
period T
T
1
t
on
t
on
t
off
T
2
contact
contact
time [s]
time [s]
DIAGR_3E.CDR
Fig. 8.5
Signal of a
pulse-length-modulated
control contact (left)
and a pulse-frequency-
modulated control
contact (right)
-100 %
100 %
W
X
u
X
X
o
Inner
range
C
ont
ro
l
c
ont
ac
t
1
C
o
nt
ro
l
c
ont
ac
t
2
Fig. 8.4
Transmission curve of a
P controller with a bent
curve
pm152e08.chp
mycom CPM 152
Controller configuration
Hauser
49
