Digital Output of DAQ Device Does Not Change

Updated Jan 10, 2018

Reported In

Hardware

  • NI-9375

Driver

  • NI-DAQmx

Issue Details

I am trying to measure the Digital Output of my NI-9375 but the value does not change. I am writing the line with a test panel. I am providing a supply voltage of 12 Volts and expect the digital output high to be around 12 Volts and the low to be around 0 V. When I measure the voltage however it is always around 9.25, it doesn't go high or low just floats there. 

Solution

If the voltage of your digital out line does not change when you change the written value to that line, there may be an issue with your physical set up. Please see the steps below to set up a basic test of your digital output. 

  1. DC Power supply to produce Vsup: Wire the Positive to Vsup, Wire the Negative to D COM.
  2. Resistor: Plug one end of the resistor to DO0 and the other end to D COM. (This resistor will be used to sink the current and act as a pull down to drive the voltage low when the output is off. See Troubleshooting Digital Output and Pulse Generation for more information on pull down resistors with these devices.)
  3. DMM: Positive of the DMM should go to the DO Pin to measure the output, the negative of the DMM Should go to D COM.
  4. Creating a Digital Output Task in MAX is better than the test panel for writing the value. In MAX select the Module and click Create Task, select Generate Signals >> Digital Output >> Line Output, then select the correct line, then click Next, then Finish after naming your task.
  5. With the DC Power Supply on, run the Digital Out Task On Demand, Monitor the DMM value as you click on and off the DigitalOut button at the top of the Task.

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