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Overcurrent Diagnostics (Analog)

    Last Modified: May 15, 2018

    Each analog input configuration has overcurrent detection. Overcurrent diagnostics in dual input and triple input configurations use the same voting strategy as threshold diagnostics. For more information on voting strategies, refer to the Voting Strategies in Dual Input (1oo2) and Triple Input (2oo3) Configurations section.

    An overcurrent condition occurs any time the input current exceeds the largest current the channel ADC can digitize, shown as ADC Full Scale in the following figure.

    Figure 1. Overcurrent Signal Diagram
    • In dual input (1oo2) configurations, an overcurrent condition on one or two channels will generate an overcurrent fault.
    • In triple input (2oo3) configurations, an overcurrent condition on two or three channels will generate an overcurrent fault.

    The User Program will read overcurrent faults based on configuration.

    Table 1. Overcurrent Faults for Analog Configurations
    Analog Configuration Available Overcurrent Faults
    Single input (1oo1) AIn.OvercurrentFault, where n is the number of the channel configured for single input
    Dual input (1oo2) AI0.OvercurrentFault or AI2.OvercurrentFault (the even-numbered channel of dual input channel pair)
    Triple input (2oo3) AI0.OvercurrentFault only

    Scan Interface will read overcurrent faults for each individual channel, regardless of configuration. In a triple input (2oo3) configuration, a single channel in an overcurrent condition will not generate an overcurrent fault in the User Program, but will report an overcurrent fault for that channel on the Check Channel Status method in LabVIEW.

    You can use overcurrent faults in two ways:

    • You check the Module failsafe box for AIn.OvercurrentFault. If an overcurrent fault occurs, the module will go into Fail-safe Mode.
    • You can use AIn.OvercurrentFault in the transition condition on the state machine diagram. If an overcurrent fault occurs, the User Program will transition to a user-configured state.

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