Programming instructions

Chapter 4 Where You Should Go Next
© National Instruments Corporation 4-3 LabVIEW Data Acquisition Basics Manual
Questions You Should Answer
1. Measuring Device: DAQ Device or SCXI Module?
Are you working in a noisy environment? If you are, then you may have
Signal Conditioning eXtensions for Instrumentation (SCXI) modules
connected to your DAQ device or the parallel port of your computer.
SCXI modules can filter and isolate noise from signals. They can also
amplify low signals. SCXI modules expand the number of channels to
acquire or generate data.
DAQ devices are primarily used alone when extra signal conditioning is not
necessary.
If you are using a DAQ device, then read question 2. If you are using SCXI,
go to Part V,
SCXI—Getting Your Signals in Great Condition
.
2. Analog or Digital Signal Analysis?
Does your signal have two discrete values that are TTL signals? If so, then
you have a digital signal. Otherwise, you have an analog signal. The type
of information you would need to know from an analog signal is the level
(discrete value), shape, and frequency content.
Analog or Digital Signal Acquisition or Generation?
If you want to measure and analyze signals from a source outside the
computer, you want to
acquire
signals. If you want to send signals to an
outside instrument to control its operation, then you want to
generate
signals.
If you want to
acquire
analog signals, go to question 4. If you want to
generate
analog signals, refer to question 5. If you want to acquire and
generate analog signals, refer to the
Using Analog Input/Output Control
Loops
section of Chapter 6,
One-Stop Single-Point Acquisition.
If you want to acquire or generate
digital
signals, read the next question.
3. Digital or Counter Interfacing?
Digital I/O interfaces primarily with binary operations, such as turning
external equipment on or off or sense logic states, such as the on/off
position of the switch. Counters generate individual digital pulses or waves
or count digital events, like how many times a digital signal rises or falls
in value.
If you are performing digital I/O, refer to question 7. If you need to use
counters, read question 8.