When performing analog input, the task can be timed to Acquire 1 Sample, Acquire n Samples, or Acquire Continuously.
Acquire 1 Sample
Acquiring a single sample is an on-demand operation. In other words, NI-DAQmx acquires one value from an input channel and immediately returns the value. This operation does not require any buffering or hardware timing. For example, if you periodically monitor the fluid level in a tank, you would acquire single data points. You can connect the transducer that produces a voltage representing the fluid level to a single channel on the measurement device and initiate a single-channel, single-point acquisition when you want to know the fluid level.
Acquire n Samples
One way to acquire multiple samples for one or more channels
is to acquire single samples in a repetitive
manner. However, acquiring a single data sample on one or
more channels over and over is inefficient and time
consuming. Moreover, you do not have accurate control over
the time between each sample or channel. Instead you can use
hardware timing, which uses a buffer in computer memory, to
acquire data more efficiently. Programmatically, you need to
include the timing function and specify the sample
rate and the sample mode (finite). As
with other functions, you can acquire multiple samples for a
single channel or multiple channels.
With NI-DAQmx, you also can gather data from multiple channels. For instance, you might want to monitor both the fluid level in the tank and the temperature. In such a case, you need two transducers connected to two channels on the device.
Acquire Continuously
If you want to view, process, or log a subset of the samples
as they are acquired, you need to continually acquire
samples. For these types of applications, set the
sample mode to continuous.
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