Types of Virtual Channels

You can create a number of different types of virtual channels, depending on the signal type—analog, digital, or counter—and direction (input or output). These channels can be either global virtual channels or local virtual channels. For information on specific functions/VIs, refer to the NI reference help for your ADE.

• Analog Input Channels—Analog input channels measure different physical phenomena using a variety of sensors. The type of channel to create depends on the type of sensor and/or phenomenon you want to read. For instance, you can create channels for measuring temperature with a thermocouple, measuring current, measuring voltage, and measuring voltage with excitation.
• Analog Output Channels—NI-DAQmx supports two types of phenomena, voltage and current. You can use custom scales if the output from the device relates to another unit of measure.
• Digital Input/Output Channels—For digital channels, you can create both line-based and port-based digital channels. A line-based channel can contain one or more digital lines from one or more ports on a device. Reading or writing to a line-based channel does not affect other lines on the hardware. You can split lines in a particular port among multiple channels and use those channels simultaneously within one or multiple tasks, but the lines in a given channel must all be input lines or all be output lines. Additionally, all channels in a task must be either input channels or output channels. Some devices also require that the lines of a given port all be input lines or output lines. Check your device documentation for the capabilities of your device.

  A port-based channel represents a fixed collection of lines on the device. Reading or writing to a port affects all the lines on the port. The number of lines in the port (commonly referred to as port width) is hardware dependent and typically varies from 8 lines (MIO device) to 32 lines (SCXI digital modules).

• Counter Input/Output Channels—NI-DAQmx supports several types of counter input and output channels for different types of counter measurements and generations. To find out more about counter measurements and terminals used for common applications, refer to Counter Parts in NI-DAQmx.