Programming instructions

© National Instruments Corporation 10-1 LabVIEW Data Acquisition Basics Manual
10
Things You Should Know
about Analog Output
Some measuring systems require that analog signals be generated by a data
acquisition (DAQ) device. Each of these analog signals can be a steady or
slowly changing signal, or a continuously changing waveform. The next
few sections show you how to use LabVIEW to produce all of these
different types of signals. First, you should learn about the various
situations in which you might need to produce an analog signal.
Single-Point Output
When the signal level at the output is more important than the rate at which
the output value changes, you need to generate a steady DC value. You can
use the single-point analog output VIs to produce this type of output. With
single-point analog output, any time you want to change the value on an
analog output channel, you must call one of the VIs that produces a single
update (a single value change). Therefore, you can change the output value
only as fast as LabVIEW calls the VIs. This technique is called
software
timing
. You should use software timing if you do not need high speed
generation or very accurate timing. Refer to Chapter 11,
One-Stop
Single-Point Generation
, for more information on single-point output.
Buffered Analog Output
Sometimes in performing analog output, the rate that your updates occur is
just as important as the signal level. This is called
waveform generation
, or
buffered analog output
. For example, you might want your DAQ device to
act as a function generator. You can do this by storing one cycle of sine
wave data in an array, and programming the DAQ device to generate the
values continuously in the array one point at a time at a specified rate. This
is known as
single-buffered waveform generation
. But what if you want to