Channel expansion is the process of expanding the channels of a data acquisition device to include channels of another device, effectively creating a task with more channels. When channel expansion is utilized, DAQmx automatically routes triggers and clocks in the DAQmx driver level so that the multiple devices are synchronized. This synchronization is necessary in order to make the devices function as one. Channel Expansion is one of the easiest and often most precise way to synchronize multiple DAQmx devices.
Additionally, multiple DAQmx Create Virtual Channel instances can be combined in one DAQmx task, even when channel expansion is used. This allows a single DAQmx task to include different measurement types, as well as channels from multiple devices.
Channels and devices must be comma separated. Below are code samples for channel expansion in LabVIEW and LabWindows/CVI:
Channel Expansion is not supported for all NI data acquisition devices in all versions of the DAQmx driver. Multi-device task support for DSA devices began with NI-DAQmx 8.0, for S Series MIO devices beginning with NI-DAQmx 8.1, and for X Series MIO devices in DAQmx 9.0.