Each digital I/O signal is protected against overvoltage, undervoltage, and overcurrent conditions as well as electrostatic discharge (ESD) events.

Follow these guidelines to avoid these fault conditions:

  • If you configure a digital I/O line as an output, do not connect it to any external signal source, ground, or power supply.
  • If you configure a digital I/O line as an output, understand the current requirements of the load connected to these signals. Do not exceed the specified current output limits of the USB-6421. NI has several signal conditioning solutions for digital applications requiring high current drive.
  • If you configure a digital I/O line as an input, do not drive the line with voltages outside of its normal operating range. The digital I/O lines have a smaller operating range than the AI signals.
  • Treat the USB-6421 as you would treat any static sensitive device. Always properly ground yourself and the equipment when handling the USB-6421 or connecting to it.