Programming instructions

Chapter 7 Buffering Your Way through Waveform Acquisition
LabVIEW Data Acquisition Basics Manual 7-8
© National Instruments Corporation
your program, read the Do You Need To Access Your Data during Acquisition?
section in this chapter to see how to control acquisition start-up times.
Simple-Buffered Analog Input with a Write to Spreadsheet File
If you want to write the acquired data to a file, there are many file formats
in which you can store the data. The spreadsheet file format is used most
often because you can read it using most spreadsheet applications for later
data graphing and analysis. In LabVIEW, you can use VIs to send data to a
file in spreadsheet format or read back data from such a file. You can locate
these VIs in
Functions»File I/O
. The VI used in this example is the
Write to Spreadsheet File VI, shown in Figure 7-8. In this exercise, the
Intermediate analog input VIs acquire an array of data, graph the data using
the actual sample period for the x-axis timebase, and create a spreadsheet
file containing the data.
Figure 7-8.
Writing to a Spreadsheet File after Acquisition
Triggered Analog Input
For information on starting your acquisition with triggers, refer to
Chapter 8,
Controlling Your Acquisition with Triggers
.
Do You Need To Access Your Data during Acquisition?
You can apply the simple buffering techniques in many DAQ applications,
but there are some applications where these techniques are not appropriate.
If you need to acquire more data than your computer’s memory can hold,
or if you want to acquire data over long periods of time, you should not use
these simple-buffered techniques. For these types of applications, you
should set up a circular buffer to store acquired data in memory. In the
previous section, buffered input was compared to shopping for groceries.
You typically use a cart or bag (your buffer) to hold as many groceries