Table Of Contents

Fault Detection

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    Last Modified: September 6, 2017

    Digital Input Configurations

    Table 1. Single Input
    Fault Input Signal Status
    Low High
    Short to ground Not detected, safe state Not detected, safe state
    Short to Vsup Not detected Not detected
    Open circuit Not detected, safe state Not detected, safe state
    Table 2. Single Input with Test Pulse
    Fault Switch Condition
    Open Closed
    Short to ground (test pulse output channel) Overcurrent fault Overcurrent fault
    Short to Vsup (test pulse output channel) Not detected, safe state Test pulse fault
    Short to ground (input channel) Not detected, safe state Overcurrent fault
    Short to Vsup (input channel) Test pulse fault Test pulse fault
    Open circuit Not detected, safe state Not detected, safe state
    Table 3. Equivalent Dual Input
    Fault Input Signal Status
    Low High
    Short to ground (one channel) Not detected, safe state Discrepancy fault
    Short to ground (both channels) Not detected, safe state Not detected, safe state
    Short to Vsup (one channel) Discrepancy fault Not detected
    Short to Vsup (both channels) Not detected Not detected
    Channels shorted together Not detected Not detected
    Open circuit (one channel) Not detected, safe state Discrepancy fault
    Open circuit (both channels) Not detected, safe state Not detected, safe state
    Table 4. Complimentary Dual Input
    Fault Input Signal Status
    Low High
    Short to ground (one channel) Not detected Discrepancy fault
    Short to ground (both channels) Discrepancy fault Discrepancy fault
    Short to Vsup (one channel) Discrepancy fault Not detected
    Short to Vsup (both channels) Discrepancy fault Discrepancy fault
    Channels shorted together Discrepancy fault Discrepancy fault
    Open circuit (one channel) Not detected Discrepancy fault
    Open circuit (both channels) Discrepancy fault Discrepancy fault
    Table 5. Equivalent Dual Input with Test Pulse
    Fault Switch Condition
    Open Closed
    Short to ground (one or both test pulse output channels) Overcurrent fault Overcurrent fault
    Short to Vsup (one or both test pulse output channels) Test pulse fault Test pulse fault
    Test pulse output channels shorted together Test pulse fault Test pulse fault
    Short to ground (one or both input channels) Not detected, safe state Overcurrent fault
    Short to Vsup (one or both input channels) Test pulse fault Test pulse fault
    Input channels shorted together Test pulse fault Test pulse fault
    Open circuit (one channel) Not detected, safe state Discrepancy fault
    Open circuit (both channels) Not detected, safe state Not detected, safe state
    Table 6. Complimentary Dual Input with Test Pulse
    Fault Switch Condition
    Open Closed
    Short to ground (one or both test pulse output channels) Overcurrent fault Overcurrent fault
    Short to Vsup (one or both test pulse output channels) Test pulse fault Test pulse fault
    Test pulse output channels shorted together Test pulse fault Test pulse fault
    Short to ground (one input channel) Not detected Overcurrent fault
    Short to ground (both input channels) Discrepancy fault Discrepancy fault
    Short to Vsup (one or both input channels) Test pulse fault Test pulse fault
    Input channels shorted together Test pulse fault Test pulse fault
    Open circuit (one channel) Not detected Discrepancy fault
    Open circuit (both channels) Discrepancy fault Discrepancy fault

    Digital Output Configurations

    Table 7. Single Output
    Fault Output Signal Value
    True False
    Short to ground Overcurrent fault Not detected, safe state
    Short to Vsup Not detected Readback fault
    Open circuit Open circuit fault Not detected, safe state
    Table 8. Single Output with Internal Test Pulse
    Fault Output Signal Value
    True False
    Short to ground Overcurrent fault Not detected, safe state
    Short to Vsup Test pulse fault Readback fault
    Open circuit Open circuit fault Not detected, safe state
    Table 9. Single Output with External Test Pulse
    Fault Output Signal Value
    True False
    Short to ground (output channel) Overcurrent fault Not detected, safe state
    Short to Vsup (output channel) Test pulse fault Readback fault
    Short to ground (input channel) Overcurrent fault Not detected, safe state
    Short to Vsup (input channel) Test pulse fault Readback fault
    Open circuit Open circuit fault Not detected, safe state
    Table 10. Single Output with External Readback
    Fault Output Signal Value
    True False
    Short to ground (output channel) Overcurrent fault Not detected, safe state
    Short to Vsup (output channel) Not detected Readback fault
    Short to ground (input channel) Overcurrent fault Not detected, safe state
    Short to Vsup (input channel) Not detected Readback fault
    Open circuit Open circuit fault Not detected, safe state
    Table 11. Dual Output
    Fault Output Signal Value
    True False
    Short to ground (one or both channels) Overcurrent fault Not detected, safe state
    Short to Vsup (one or both channels) Not detected Readback fault
    Open circuit (one or both channels) Open circuit fault Not detected, safe state
    Table 12. Dual Output with Internal Test Pulse
    Fault Output Signal Value
    True False
    Short to ground (one or both channels) Overcurrent fault Not detected, safe state
    Short to Vsup (one or both channels) Test pulse fault Readback fault
    Open circuit (one or both channels) Open circuit fault Not detected, safe state
    Table 13. Dual Output with External Test Pulse
    Fault Output Signal Value
    True False
    Short to ground (output channel) Overcurrent fault Not detected, safe state
    Short to Vsup (output channel) Test pulse fault Readback fault
    Short to ground (input channel) Overcurrent fault Not detected, safe state
    Short to Vsup (input channel) Test pulse fault Readback fault
    Open circuit Open circuit fault Not detected, safe state

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