Setting the AI Min and Max properties controls the gain that is set for each channel on the DAQ board. You can set these inputs through the Create Channel VI or through the Channel Property Node. Once these inputs are set, the DAQmx driver will automatically pick the gain that provides the highest resolution for the acquisition over the input range specified. You can query the AI Min and Max properties at any time to see which values are being used by the driver.
However, you can't change the input range being used for a channel while the acquisition is in progress. If you want to change the input range, you will need to stop the task, reconfigure appropriately, and restart the task.
