Saturday, March 19, 2005

Sub VI Advantages

Easier to debug
Don’t have to recreate code
Require less memory

Accessing user-made subVIs
1. Functions >> Select a VI or 2. Drag icon onto target diagram

Error cluster contains the following information:
Boolean to report whether error occurred
Integer to report a specific error code
String to give information about the error
# status is a Boolean value that reports True if an error occurred. Most VIs, functions, and structures that accept Boolean data also recognize this parameter. For example, you can wire an error cluster to the Boolean inputs of the Stop, Quit LabVIEW, or Select functions. If an error occurs, the error cluster passes a True value to the function.
# code is a 32-bit signed integer that identifies the error numerically. A non-zero error code coupled with a status of False signals a warning rather than a fatal error.
# source is a string that identifies where the error occurred.

Same VI, viewed three different ways
Yellow field designates a standard VI
Blue field designates an Express VI
•Express VIs: interactive VIs with configurable dialog page
•Standard VIs: modularized VIs customized by wiring
LabVIEW 7.0 introduced a new type of subVI called Express VIs. These are interactive VIs that have a configuration dialog box that allows the user to customize the functionality of the Express VI. LabVIEW then generates a subVI based on these settings.

A strip chart shows running data continuously scrolling from left to right across the chart. A scope chart shows one item of data, such as a pulse or wave, scrolling partway across the chart from left to the right. A sweep chart is similar to an EKG display. A sweep chart works similarly to a scope except it shows the older data on the right and the newer data on the left separated by a vertical line. The scope chart and sweep chart have retracing displays similar to an oscilloscope. Because there is less overhead in retracing a plot, the scope chart and the sweep chart display plots significantly faster than the strip chart.

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