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External Overvoltage Detection

Last Modified: May 2, 2019

An external overvoltage condition occurs when an analog output channel is connected to an external voltage source that is high enough to overdrive the analog output channel. Two NI-DAQmx Write attributes/properties allow you to check for external overvoltage channels.

The first is ExternalOvervoltageChansExist. This attribute/property returns a Boolean true if one or more channels experience an external overvoltage condition. The second is ExternalOvervoltageChans. This attribute/property returns an array of strings indicating which channels (if any) experienced an external overvoltage condition. You must query the ExternalOvervoltageChansExist attribute/property before querying the ExternalOvervoltageChans attribute/property.

ExternalOvervoltageChansExist reads the external overvoltage fault condition from the device and caches it in the driver. It also resets this condition of the device after it is read. Subsequent reads of ExternalOvervoltageChans attribute/property will read the faulted channel information cached in the driver from the previous ExternalOvervoltageChansExist query.


NI-DAQmx generates all data whether or not an external overvoltage fault occurs. If your application requires external overvoltage checking, it is recommended that you read the above attributes/properties after each call to Write. Your program should discard questionable output or return a flag when the driver reports an external overvoltage.

Consult your device documentation for more information on fault reporting thresholds and capabilities specific to your device.

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