Programming instructions

© National Instruments Corporation 6-1 LabVIEW Data Acquisition Basics Manual
6
One-Stop Single-Point
Acquisition
This chapter shows you how to acquire one data point from a single channel
and then one data point from each of several channels using LabVIEW.
Single-Channel, Single-Point Analog Input
A single-channel, single-point analog input is an immediate, non-buffered
operation. In other words, the software reads one value from an input
channel and immediately returns the value to you. This operation does
not require any buffering or timing. You should use single-channel,
single-point analog input when you need one data point from one channel.
An example of this would be if you periodically needed to monitor the fluid
level in a tank. You can connect the transducer that produces a voltage
representing the fluid level to a single channel on your DAQ device and
initiate a single-channel, single-point acquisition whenever you want to
know the fluid level.
For most basic operations, use the AI Sample Channel VI, located in
the
Functions»DAQ»Analog Input
palette. The Easy Analog Input VI,
AI Sample Channel, measures the signal attached to the channel you
specify on your DAQ device and returns the scaled value. Figure 6-1 shows
how to wire this VI.
Figure 6-1.
AI Sample Channel VI
Note
If you set up your channel in the DAQ Channel Wizard, you do not need to enter
the device or input limits. Instead, enter a channel name in the channel input, and
the value returned is relative to the physical units you specified for that channel in
the DAQ Channel Wizard. If you specify the input limits, they are treated as being
relative to the physical units of the channel. LabVIEW ignores the device input
when channel names are used. This principal applies throughout this manual.