GOSSEN-METRAWATT GMBH
34
Performing an oscillation test
If it is not possible to perform a trial run, e.g. where adjacent control loops strongly influence the actual value, or where an active switching output is
required to hold the actual value (working point of cooling), or where certain reasons require optimizing to the set point, the control parameters can be
established by means of a continuous oscillation. However, the calculated values for
tu
could eventually be very inaccurate in this case.
– Get started as described above. It is possible to perform the test without a recorder, if the actual value is watched on the display and the times on a timer.
– Set
dbnd
=
0
for three-state, split range and step controllers.
– Activate the control elements in
automatic mode
, eventually start a recorder. Record several oscillations until they are alike.
– Measure out the
oscillation width
x
ss
.
– Record the
On time
T
I
and the
Off time
T
II
of the switching output I and/or the continuous output of the oscillations.
Evaluation of the oscillation test
Parameter values
tu
1)
0.3
•
(T
I
+ T
II
)
0.2
•
(T
I
+ T
II
– 2
tY
)
tc
tu
/ 12
tY
/ 100
Pb I
x
ss
•
100 %
MBU
x
ss
•
T
II
•
100 %
MBU (T
I
+ T
II
)
x
ss
•
200 %
MBU
x
ss
•
T
II
•
200 %
MBU (T
I
+ T
II
)
x
ss
•
50 %
MBU
Pb II
–
Pb I
•
(T
I
/ T
II
)
–
Pb I
•
(T
I
/ T
II
)
–
Parameter
Two-state controller
3-state controller
Contin. controller
Split range controller
Step controller
T
I
T
II
x
ss
Содержание R2600
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