
Control and fine-optimisation of set parameters using a recorder
Actuating signal outputs (R237 ... R2310)
The control contact in question outputs a switched signal. The intensity of this signal is
proportional to the controller’s control output. A distinction is made according to the type of
signal output:
•
Pulse length modulation
The greater the calculated control output
the longer the contact in question remains
picked up. The period can be adjusted
between 0.5 and 99 s. Pulse length-
modulated outputs are used to control
solenoid valves.
•
Pulse frequency modulation
The greater the calculated control output,
the higher the switching frequency of the
contact. The maximum switching
frequency 1/T can be adjusted between 60
and 180 min
–1
. The ON period t
ON
is
constant. Pulse frequency-modulated
outputs are used to control solenoid
operationed metering pumps.
REGEL02.CDR
Actual
value
Actual
Actual
value
Actual
Actual
T
n
too small
T
n
too large
K
p
too small
K
p
too large
Optimal setting
Time
Time
Time
Time
Time
Fig. 5.11
Optimisation of settings
T
n
and K
p
IMPULS.CDR
t
ON
t
OFF
On
Off
Period length T Time [s]
Contact
Contact
t
ON
T1 T2 Time
On
Off
Fig. 5.12
Signal of a pulse
length-modulated (left)
and a pulse frequency-
modulated (right)
regulating contact
Instrument configuration Liquisys M CPM 223 / 253
40 Endress+Hauser
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