Endress+Hauser PROline Prosonic Flow 93 Function Manual page 195

PROline Prosonic Flow 93 FOUNDATION Fieldbus
Endress+Hauser
6.8 Example: Basic PID control
The continual flow into a container is to be controlled.
The volume flow of the fluid is captured via a flow transmitter (FT) and made available to
the PID function block via an Analog Input function block. The PID function block may
be either in the flowmeter or in the control valve. The manipulated variable that is
forwarded to the control valve (FV) is calculated in the PID function block using the
deviation between the measured volume flow and the specified setpoint value (desired
volume flow).
Fig. 6: PID control for continual flow into a container
Connecting the function blocks
The PID function block receives its input value (controlled variable) from an Analog Input
function block (OUT output value). This input value, which corresponds to the measured
volume flow of the flowmeter, is read into the PID function block via the IN parameter,
(see Page 207).
In the AUTO operating mode, the setpoint value is specified manually via the SP
parameter, (see Page 214).
The manipulated variable calculated in the PID function block is connected to the
CAS_IN input parameter of the Analog Output function block via the output value OUT,
(see Page 211). The Analog Output function block forwards this manipulated variable
to the control valve.
In addition, the BKCAL_OUT output parameter of the Analog Output function block is
read in via the BKCAL_IN input parameter, (see Page 201), of the PID function block to
ensure bumpless switching of the operating mode.
Fig. 7: Connecting the function blocks
6 PID function block (PID controller)
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