Why is my NI-9472 Digital Output Card Not Actuating my Valve?

Updated Aug 4, 2020

Reported In

Hardware

  • NI-9472

Issue Details

I bought an NI-9472 Digital Output card that meets the operating voltage and current requirements for the valve, but when I try to operate the valve, it won't move. If I connect the valve directly to my power supply, it works correctly.

Solution

The NI-9472 includes overcurrent protection that will disable the output channel and won't return to normal operation until the module is manually reset. When operating valves, it is common that the starting current is significantly larger than the steady state value for a short time period. In the case of the NI-9472, this could cause the overcurrent protection to trip. It is important to characterize this inrush current to make sure the module can handle it, or otherwise find a way to mitigate it.

Additional Information

The starting current (or inrush current) may look significantly lower when connecting the valve directly to the power supply due to the output control circuitry present in most power supplies.