OpenChansExist returns a Boolean of true if one or more channels were disconnected since the last time the attribute/property was queried, and OpenChans returns the virtual channel names of the channels that were disconnected. You must query the OpenChansExist attribute/property before querying the OpenChans attribute/property.

OpenChansExist reads the open channel condition from the device and caches it in the driver. Subsequent reads of OpenChans attribute/property will read the channel information cached in the driver from the previous OpenChansExist query.

NI-DAQmx returns all data whether an open channel is detected. If your application requires open channel checking, it is recommended that you read the open channel attributes/properties after each call to Read/Write. Your program should discard questionable data or return a flag when the driver reports an open channel.

You can also check for shorted channels using the DAQmx Read OvercurrentChansExist and OvercurrentChans attributes/properties. Refer to Overcurrent Detection.