Note
Refer to the IEC 61131-2 standard for more
information about short-circuit-proof devices.
Note
Because the NI 9475 includes internal flyback
diodes, you do not need to add external diodes when
connecting to switching devices that store energy.
Detecting an Overcurrent Condition
If a device connected to the module is not working while the
channel is on, the module channel may be in an overcurrent state.
Neither the software nor the module LEDs indicate if an
overcurrent condition occurs. A channel LED may be on even if
the channel is off because of an overcurrent condition.
To determine if the channel is in an overcurrent state, measure the
voltage between DO and Vsup. If the voltage is equal to the
voltage of the external power supply connected to the module,
the channel is in an overcurrent state.
Power Supplies and Overcurrent Conditions
If a short-circuit occurs, the current through DO can exceed the
current rating for the power supply and the maximum continuous
output current for the NI 9475.
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NI 9475 Getting Started Guide
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