In DAQmx 7.2 and earlier, the DAQ Assistant will not allow you to add multiple virtual channels to the same task unless they are the exact same type.
With NI-DAQ™mx 7.2, you can add multiple virtual channels to a task in the DAQ Assistant, but the virtual channels must be of the same measurement type (voltage, temperature, strain, etc) as well as the same I/O type (analog input, counter output, etc). For example, if your first virtual channel is an analog input voltage virtual channel, all other virtual channels must also be analog input voltage channels (i.e. analog input strain channels will not work with this particular task).
To include virtual channels of different measurement types in a task, you will first need to verify that you have NI-DAQmx 7.3 or later installed.
With current versions of DAQmx, a single NI-DAQmx Task can have virtual channels of multiple measurement types as long as they are part of the same I/O type. For example, voltage readings and temperature readings both fall under the analog input I/O type, so we can use both virtual channel measurement types in the same NI-DAQmx Task. To add a virtual channel of a different measurement type to a task, click the Add Channels
button as the following image illustrates.
Add other type of measurement