ADS Environmental Services FlowShark Pulse QR 775004 A1 - Manual (Page 132)

8-42 ADS FlowShark Pulse O&M Manual
Shorter intervals will accelerate the control behavior; however, they will cause the
control circuit to oscillate when longer run times exist between the regulating unit
and measurement.
A longer interval will decrease the tendency for the controller to oscillate; however, it
will increase the inertia of the regulating system.
Guideline:
average flow velocity
Interval =
distance between regulating unit and measurement
• 1.3
Control deviation
This parameter defines the amount of deviation that can occur from the setpoint of the
control system without executing a regulating event. This setting reduces the
tendency for the system to oscillate. Hydraulic conditions cause volume
measurements to fluctuate. If there is no tolerance defined for setpoint deviation, the
system will repeatedly attempt to adjust the actual value according to the setpoint.
This may cause the regulating unit to run continuously, potentially resulting in
mechanical defects or deterioration.
Both values have an AND logic relationship to each other. Under this condition, it
typically is sufficient to define a percentage value.
Consider entering an absolute value for external setpoint control (channel network
management) and large controlling ranges. Otherwise, for low setpoints, the
permissible control deviation percentage may be very low. Inputting an absolute
value as well will help avoid control oscillations under these conditions.
Figure 8-60 Setting permissible control deviations
Minimum duration of control impulse
This parameter is similar to the I-component of PID controllers. It defines the
minimum regulating time for a regulating unit to ensure that very short calculated
control impulses mechanically affect the regulating unit. Therefore, specify a longer
duration for the minimum control impulse than required for the combined motor start-
up time, gear clearance, and slide valve clearance.