The NI 9265 can detect if there is an insufficient external power or no external power connected to the Vsup terminal. Two NI-DAQmx Read attributes/properties allow you to check the external power. The first is PowerSupplyFaultChansExist. This attribute/property returns a Boolean true if one or more channels lack external power. The second is PowerSupplyFaultChans. This attribute/property returns an array of strings indicating which channels (if any) experienced a power supply fault. You must query the PowerSupplyFaultChansExist attribute/property before querying the PowerSupplyFaultChans attribute/property.