Standard Control Mode; Autotune Function - Burkert 8718 Operating Instructions Manual

Type 8718, 8719 / 8708, 8709
Operation and function
8.3.1.

Standard control mode

The LFC / LFM is in this operating state immediately after the device is switched on, after a brief initiali-
sation phase. The green Power LED is lit.
The flow-rate is corrected for the LFC to the specified set-point value at a high dynamic.
Malfunctions, e.g. due to pressure changes, are quickly counterbalanced by a corresponding adjustment of
the proportional valve position.
The set-point value is specified in this operating state depending on the device version via the analogue
input (standard signal input) or the field bus.
The controller parameters are set in such a way that set-point value changes or actuating variables are cor-
rected as quickly as possible without appreciable overshoot occurring.
The actual flow-rate value can be read depending on the device version via the analogue output (standard
signal output) or the field bus.
Please note!
If the blue limit (y) LED lights up, this means
• for the LFC
the control signal of the proportional valve is approaching the 100 % limit.
The cause is usually
T his may cause the specified set-point value not to be reached and result in a permanent positive
control deviation (w – x).
• for the LFM
the current flow-rate is approaching the nominal flow-rate or has exceeded it.
If the nominal flow-rate is greatly exceeded, this may cause the output flow-rate to deviate from the
actual flow-rate.
To give an external response to the deviations, a binary output is switched.
8.3.2.

Autotune function

A prerequisite for the automatic adjustment of the controller, to the conditions of the system, is that typical
pressure conditions prevail.
→
Activate the Autotune function by briefly actuating (> 0.5 s) the binary input 1.
The Autotune function runs automatically.
While the Autotune function is running, the green Power LED flashes.
WARNING!
While the Autotune function is running, note the following:
Different flow-rate changes occur.
• The power supply of the LFC must not be switched off.
• The supply pressure should be kept constant.
- a too low pressure difference via the LFC,
e.g. due to an inadequate pressure supply or
- a heavily soiled filter.
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