Continuous Measurement and Logging (NI-DAQmx)

The Continuous Measurement and Logging (NI-DAQmx) sample project acquires measurements continuously and logs them to disk. It executes five loops in parallel:

• Event handling (Main.vi)—The Event Handling Loop that produces messages based on front panel events, such as the user clicking Start or Settings.
• User interface messaging (Main.vi)—A Message Handling Loop that receives messages from the Event Handling Loop and responds by sending messages to the other Message Handling Loops.
• Acquiring data (Acquisition.lvlib:Acquisition Message Loop.vi)—A Message Handling Loop that continuously acquires data.
• Logging data (Logging.lvlib:Logging Message Loop.vi)—A Message Handling Loop that continuously logs acquired data.
• Displaying data (Main.vi)—A While Loop that updates the waveform chart with acquired data.

This sample project also features a Settings dialog box (Settings.lvlib) you can use to configure the application.

This sample project is based on the Queued Message Handler template. Refer to the Queued Message Handler template and its documentation, available from the Create Project dialog box, for information about how this template works.

System Requirements

Requirements

LabVIEW Base Package and NI-DAQmx driver software.

Project Diagram

This sample project uses the NI-DAQmx API to configure and acquire a measurement with hardware I/O.

Use Cases

The Continuous Measurement and Logging (NI-DAQmx) sample project is designed for a continuous measurement application that requires a responsive user interface; that is, users should be able to click buttons even while the application is executing another command.

Running this Sample Project

1. In the Project Explorer window, open and run Main.vi.
2. Click Start. The program begins acquiring waveform data.
3. Click the other front panel buttons to explore the sample project.

Customizing this Sample Project

If the default logging behavior does not meet the needs of your application, you can modify this sample project in the following ways:

• To specify where data is logged, run Main.vi, click Settings, and use the Log File Path control. By default, this template logs data to LabVIEW Data\Logged Data.tdms, where LabVIEW Data is the LabVIEW Data folder.
• To specify a trigger for logging data, run Main.vi, click Settings, and use the Log When Triggered control. You can specify a time or threshold value to trigger logging. You can also manually trigger logging by using the Force Trigger control on Main.vi.
• To change the data logging mechanism, modify Logging.lvlib:Logging Message Loop.vi. For example, you could modify this VI to stream acquired data across a network or to disk. By default, this template uses notifiers to control when data is logged.
• To change the code that writes data to disk, modify Logging.lvlib:Log Data.vi. For example, you could use the Export Waveforms to Spreadsheet File or Write to Spreadsheet File VIs.
• To change or add path and file refnums that are needed for data logging, modify Logging.lvlib:Logging Configuration.ctl.
• To change the type of data this acquisition acquires, open Configure Hardware.vi, and select a different instance of the DAQmx Create Virtual Channel VI.

If the default logging behavior is too slow for your application, you can use the DAQmx Start New File and DAQmx Configure Logging VIs. Refer to the VI documentation for more information.

Additional Resources

Refer to the LabVIEW Help, available by selecting Help»LabVIEW Help for information about LabVIEW concepts or objects used in this sample project. You can also use the Context Help window to learn basic information about LabVIEW objects as you move the cursor over each object. To display the Context Help window in LabVIEW, select Help»Show Context Help.

Important Information

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