National Instruments BridgeVIEW 用户手册

Chapter 11

Loops and Charts

© National Instruments Corporation

11-9

b.

Pop up on the switch and choose Data Operations»Make 
Current Value Default. This makes the ON position the default 
value.

c.

Pop up on the switch and choose Mechanical Action»Latch 
When Pressed.

3.

Run the VI. Click on the 

Enable

 switch to stop the acquisition. 

The switch moves to the OFF position momentarily and is reset back 
to the ON position.

4.

Save the VI.

Note

Mechanical Action of Booleans.vi

Examples\G Examples\General\Controls\booleans.llb.

End of Activity 11-3.

Timing

When you ran the VI in the previous activity, the While Loop executed as 
quickly as possible. However, you can slow it down to iterate at certain 
intervals with the functions in the Functions»Time & Dialog palette.

The timing functions express time in milliseconds (ms), however, your 
operating system might not maintain this level of timing accuracy. 
On Windows 95/NT, the timer has a resolution of 1 ms. This is 
hardware-dependent, so on slower systems, such as an 80386, you might 
have lower resolution timing.

Activity 11-4. Control Loop Timing

1.

Open 

Random Signal.vi

, as modified and saved in Activity 11-3, 

from the 

BridgeVIEW\Activity

 directory.

2.

Modify the VI to generate a new random number at a time interval 
specified by the knob, as shown in the following illustration.