Bürkert 8792, Operating Instructions Manual

Page: 82 / 196

82
Basic setting of the process controller
Type 8792, 8793 REV.2
15.5.1 The operating mode of
P.TUNE
The P.TUNE function automatically identifies the process. To do this, the process is activated with a defined
disturbance variable. Typical process characteristics are derived from the response signal and the structure
and parameters of the process controller are determined on the basis of the process characteristics.
When using
P.TUNE self-optimization, optimum results are obtained under the following conditions:
•
Stable or stationary conditions concerning the process actual value PV when starting P.TUNE .
•
Execution of P.TUNE in the operating point or within the operating range of the process control.
15.5.2 Preparatory measures for execution of P.TUNE
The measures described below are not compulsory conditions for running the P.TUNE function.
However, they will increase the quality of the result.
The P.TUNE function can be run in the MANUAL or AUTOMATIC operating state.
When P.TUNE is complete, the control system is in the operating state which was set previously.
15.5.2.1. Preparatory measure for execution of
P.TUNE
in the MANUAL
operating state
Move the process actual value up to the operating point as follows:
→
/ Select PV . The process actual value PV is indicated on the display.
→
Select MANU . Change to MANUAL operating state.
The input screen for manually opening and closing the valve is displayed.
→
Open valve OPN or close valve CLS
By opening or closing the control valve, move the process actual value to the required operating point.
→
As soon as the process actual value PV is constant, the P.TUNE function can be started.
You have moved the process actual value PV to the operating point.
15.5.2.2. Preparatory measure for execution of
P.TUNE
in the AUTOMATIC
operating state
By inputting a process set-point value SP , move the process actual value PV to the operating point.
Observe the internal or external set-point value default for the input
( P,CONTROL → SETUP → SP-INPUT → internal/external) :
For internal set-point value default: Input the process set-point value
SP
via the device keyboard
(see description below “Table 50”).
For external set-point value default: Input the process set-point value SP via the analog set-point
value input.
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