Can I Use Pull-Down Resistors for Analog Inputs?

Updated Jul 12, 2018

Reported In

Software

  • LabVIEW

Driver

  • NI-DAQmx

Issue Details

I notice that my voltages are floating when I have a disconnected or open channel and would like them to read zero when they are disconnected. How can I do this?

Solution

To pull your output to zero, you can try adding a pull-down resistor between your input terminal and ground. While your input is connected, the voltage will go into the device if it has a lower resistance than the device input. If you do not have your input wires attached, the input will read in the value of ground through the resistor. A 10k ohm resistor is recommended. See related links for more information on pull-down resistors.

Additional Information

  • Added a resistor may have an impact on your analog input readings since they will change the load going to the ADC. If you add a pull-down resistor, check your readings after to make sure that it has not affected them.
  • Another approach hasn't been tested and it will require of electronics understanding. It will be about using some switching device (a BJT, for example) to have the analog input connected to the original load and, once this is disconnected, it allows a path to ground avoiding the floating measurement. It's important to mention that you'll need to consider the DAQ device's specifications and the measurement you are taking as well as the device you want to use as a switch.
  • It's always possible to create a software filter or programmatic "conditioning stage". Generally, an abrupt change of the voltage will mean that the load was disconnected. Make sure you test this before deploying the application.

WAS THIS ARTICLE HELPFUL?

Not Helpful