Burkert Type 8709 - Manual (Page 13)

13
System Description
p
1
p
2
Fig. 2: Flow-rate measurement; Differential pressure method
properties of the differential pressure method
This measuring method has very short response times and therefore also allows very short sampling rates by •
the control electronics.
The measurement occurs statically, no moving parts are required in the fluid. •
control electronics 5.2.4.
Microprocessor electronics process the current set-point and actual flow-rates and control the actuating element.
The sensor signal is processed by the control electronics and is converted by the calibration curve stored in the
device into a value corresponding to the actual flow-rate.
To control critical processes, where quick flow-rate changes are not permitted, a ramp function can be activated
via the "Mass Flow Communicator" software (see Chapter
10.1.3. Mass Flow Communicator (PC software)).
In doing so, the parameters for an ascending and a descending set-point value can be set separately.
More detailed information on the ramp function and on all other functions can be found in the software
documentation for the LFC / LFM.
control deviation:
Control deviation = Set-point value – Actual value
x
d
= w – x
The control deviation is processed according to a PI control algorithm.
The control parameters are set at the factory.
To take account of the properties of the control path, the controller operates with path-dependent amplification
factors. When the autotune function runs, these are determined automatically.
english
Type 8718, 8719 / 8708, 8709