Channels and Tasks in NI-DAQmx

Taking an NI-DAQ™mx Measurement in LabVIEW™

Edition Date: February 2012

Part Number: 370689M-01

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A physical channel is a terminal or pin at which you can measure or generate an analog or digital signal. A virtual channel is a collection of property settings such as a name, a physical channel, input terminal connections, the type of measurement or generation, and can include scaling information. In NI-DAQmx, virtual channels are integral to every measurement. In Traditional NI-DAQ (Legacy) and earlier versions, configuring virtual channels is an optional way to record which channels are being used for different measurements.

In NI-DAQmx, you can configure virtual channels with the DAQ Assistant, which you can open from MAX or your application software. You also can configure virtual channels with the NI-DAQmx API in your application program. In Traditional NI-DAQ (Legacy), you configure virtual channels using MAX.

A task, an important concept for NI-DAQmx, is a collection of one or more virtual channels with timing, triggering, and other properties. Conceptually, a task represents a measurement or generation you want to perform. You can set up and save all of the configuration information in a task and use the task in an application.

In NI-DAQmx, you can configure virtual channels as part of a task or separate from a task. Virtual channels created inside a task are local virtual channels. Virtual channels defined outside a task are global virtual channels. You can create global virtual channels in MAX or in your application software and then save them in MAX. You can use global virtual channels in any application or add them to a number of different tasks. If you modify a global virtual channel, the change affects all tasks in which you reference that global virtual channel.

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