National Instruments FieldPoint FP-PWM-520 Operating Instructions Manual page 5

Detecting an Overcurrent Condition
To determine whether an overcurrent condition exists, complete
the following steps:
1. Use the FieldPoint Explorer to set the duty cycle to 100% for
the channel in question.
2. Measure the voltage between the V
that channel.
Under normal load conditions, the V
within 1 V of the supply voltage when the output is on
continuously. Any voltage more than 1 V less than the supply
voltage indicates an overcurrent condition. Typically, the
V -to-COM voltage is nearly zero if the protection circuitry
out
is activated.
The overcurrent protection circuitry resets when the output
switches to the OFF state, when you disconnect field power from
the module, when you remove the FP-PWM-520 from its terminal
base, or when you turn off the network module. Unless you set the
output duty cycle to 0% or 100%, the output channel switches to
the OFF state once per output period during normal operation.
Remedying an Overcurrent Condition
To remedy an overcurrent condition, determine the cause of the
overcurrent condition and disconnect the load that is causing the
problem from the FP-PWM-520. The channel resets automatically
when the load is removed.
Alternatively, if completely removing the channel load is not
convenient, reset the channel in any of the following ways:
• Use the FieldPoint Explorer to set the duty cycle to any value
other than 100% and wait at least one output period for the
channel to reset.
• Use the FieldPoint Explorer to set the duty cycle to 0%.
The channel resets immediately.
• Disconnect the external power supply from the module.
• Remove the FP-PWM-520 from the terminal base.
• Turn off the network module that the FP-PWM-520 is
connected to.
Normal operation can resume after you correct the overcurrent
condition.
© National Instruments Corp.
and COM terminals for
out
-to-COM voltage is
out
5 FP-PWM-520