Basic usage is presented here. For further details, see the documentation.

Basic usage

Create the acquisition object

The first step to starting the measurement is to create an acquisition object. Depending on your measurement hardware, you can select the appropriate acquisition class.

In this example, we use the LDAQ.national_instruments.NIAcquisition class, which is a wrapper for the National Instruments DAQmx driver. The class accepts the name of the input task (created in NI MAX) as an argument:

acq = LDAQ.national_instruments.NIAcquisition(input_task_name, acquisition_name='NI_data_source')

The acquisition_name argument is important when using multiple acquisition objects in the same measurement, and when specifying the layout of the live visualization.

Create the Core object

The acq object can now be added to the LDAQ.Core class, which handles the acquisition and generation of signals, and the live visualization of the measurement:

ldaq = LDAQ.Core(acquisitions=[acq])

Note

To add live visualization of the measurement, the visualization LDAQ.Visualization object can be added to the LDAQ.Core object:

ldaq = LDAQ.Core(acquisitions=[acq], visualization=vis)

Read how to prepare the vis object in the visualization section.

Set the trigger

Often the measurement is started when one of the signal excedes a certain level. This can be achieved by setting the trigger on one of the data sources by calling the set_trigger method:

ldaq.set_trigger(
    source='NI_data_source',
    level=100,
    channel=0,
    duration=11,
    presamples=10
)

Where:

• source: the name of the acquisition object on which the trigger is set.
• level: the trigger level.
• channel: the channel on which the trigger is set.
• duration: the duration of the trigger in seconds.
• presamples: the number of samples to be acquired before the trigger is detected.

Note

The LDAQ.Core may seem unnecessary when using a single acquisition source. However, it enables the usage of signal generation, live visualization and multiple acquisition/generation sources.

Run the measurement

The measurement can now be started by calling the run method:

ldaq.run()

Save the measurement

After the measurement is completed, the data can be saved by calling:

ldaq.save_measurement(
    name='my_measurement',
    root=path_to_save_folder,
    timestamp=True,
    comment='my comment'
)

Where:

• name: required, the name of the measurement, without extension (.pkl is added automatically).
• root: optional, the path to the folder where the measurement will be saved. If it is not given, the measurement will be saved in the current working directory.
• timestamp: optional, add a timestamp at the beginning of the file name.
• comment: optional, a comment to be saved with the measurement.

What else can I do with LDAQ?

• Add signal generation to the LDAQ.Core object. (see generation)
• Add visualization to the LDAQ.Core object. (see visualization)
• Apply functions to measured data in real-time visualization. (see visualization)
• Apply virtual channels to acquisition objects, to perform calculations on the acquired data. (see virtual channels)
• Add multiple acquisition and signal generation objects to LDAQ.Core. (see multiple sources)
• Define a NI Task in your program and use it with LDAQ. (see NI Task)
• Create your own acquisition class by overriding just few methods. LDAQ support signal as well as video acquisition sources. (see custom acquisition)
• Currently the package supports a limited set of devices from National Instruments, Digilent, FLIR, Basler and devices using serial communication. (see supported devices)