Gossen MetraWatt R2080 - Page 20

20 GOSSEN METRAWATT GMBH
– dbnd = 0 Setting for 3-step and step-action controllers
– Activate the actuators with automatic operation, and start the recorder if applicable. Record several
oscillations until they become uniform in size.
–Measure oscillation amplitude x
ss
.
–Record on-time T
I
and off-time T
II
at switching output I for the oscillations.
Evaluating the Oscillation Test
1) If either T
I
or T
II
is significantly greater than the other, value tu is too large.
Correction for step-action controllers in the event that T
I
or T
II
is smaller than tY:
tY
• tY tY • tY
Multiply Pb 1 by , if T
I
is smaller, or by , if T
II
is smaller.
T
I
• T
I
T
II
• T
II
The value for tu is very inaccurate in this case. It should be optimized in the closed loop control mode.
Closed Loop Control Mode
The closed loop control mode is started after self-tuning has been completed:
– Configure the desired control algorithm with controller sort.
–Adjust the setpoint to the required value.
– The dead band can be increased from dbnd = 0 for 3-step and step-action controllers if control of switching
output I and II changes too rapidly, for example due to an unsteady actual value.
Parameter Values
tu
1)
0,3 • (T
I
+ T
II
)0,2 • (T
I
+ T
II
– 2tY)
tc tu / 12 tY / 100
Pb 1 x
ss
• 100 %
MRS
x
ss
• T
II
• 100 %
MRS (T
I
+ T
II
)
x
ss
• 50 %
MRS
Pb 11 – Pb 1
• (T
I
/ T
II
)–
Parameter 2-step controller 3-step controller Step-action controller
T
I
T
II
x
ss