National Instruments NI-FBUS User Manual

Page 64

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Chapter 3

NI-FBUS Configurator Tutorials

NI-FBUS Configurator User Manual

3-6

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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.

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