National Instruments NI-FBUS User Manual
Page 64
Chapter 3
NI-FBUS Configurator Tutorials
NI-FBUS Configurator User Manual
3-6
ni.com
5.
In the PID block configuration window, select the Tuning tab. Enter
parameters appropriate for your process, as shown in the following
example.
GAIN
10
RESET
3.5 sec
BAL_TIME
0 sec
6.
Set the PID scaling parameters. The
PV_SCALE
of the PID block
(which tells the PID the range of its
IN
parameter) should match the
OUT_SCALE
of the AI block (the range of the value that the AI is
passing to the PID). Likewise, the
OUT_SCALE
of the PID block
(the range of the value that the PID is passing to the AO) should match
the
PV_SCALE
of the AO block (which gives the AO the range of its
CAS_IN
parameter).
PV_SCALE
EU_100
400
EU_0
-100
Units_Index
°C
Decimal
3
OUT_SCALE
EU_100
400
EU_0
-100
Units_Index
°C
Decimal
3
7.
If desired, use a second AI block to specify the setpoint of the PID.
a.
Drag another AI block onto your Function Block Application
Editor window.
b.
Connect the
OUT
of the new AI block to the
CAS_IN
of the PID
block. The
OUT_SCALE
of the new AI block should match the
PV_SCALE
of the PID block. Adjust the AI and PID parameters as
needed. An example of how the final Function Block Application
Editor window should look is shown in the following figure.