National Instruments BridgeVIEW User Manual download pdf (Page 254)

Chapter 11 Loops and Charts

Wait Until Next ms Multiple function (Functions»Time & Dialog)

—This function ensures that each iteration of the loop occurs no faster

than the millisecond input. The input is 500 milliseconds for this

activity. If you pop up on the icon and choose Show»Label, the label

Wait Until Next ms Multiple appears.

6. Pop up on the input of the Wait Until Next ms Multiple function and

select Create Constant. A numeric constant appears and is

automatically wired to the function.

7. Type

500

in the label. The numeric constant wired to the Wait Until

Next ms Multiple function specifies a wait of 500 milliseconds

(one half-second). Thus, the loop executes once every half-second.

Notice that the VI initializes the shift registers with a random number.

If you do not initialize the shift register terminal, it contains the default

value or the last value from the previous run and the first few averages

are meaningless.

8. Run the VI and observe the operation.

9. Save this VI as

Random Average.vi

in the

BridgeVIEW\Activity

directory.

Note Remember to initialize shift registers to avoid incorporating old or default data

into your current data measurements

End of Activity 11-5.

Using Uninitialized Shift Registers

You initialize a shift register by wiring a value from outside a While Loop

or For Loop to the left terminal of the shift register. Sometimes, however,

you want to execute a VI repeatedly with a loop and a shift register, so that

each time the VI executes, the initial output of the shift register is the last

value from the previous execution. To do that, you must leave the left shift

left shift register terminal unwired preserves state information between

subsequent executions of a VI.

The following illustration shows an example of a subVI that calculates the

running average of four data points. The VI uses an uninitialized shift

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National Instruments BridgeVIEW User Manual Page 254