Can Too High Input Voltage Break My Multifunction I/O Device?

Updated May 3, 2018

Reported In

Hardware

  • USB-6215
  • Multifunction I/O Device

Driver

  • NI-DAQmx

Issue Details

I am building an application where I have to read the signal from a Flow Meter using a counter. The high signal from the meter will be Vout=23 V using a 24 V power adapter. I am concerned this would break my USB-6215. What can I do?

Solution

23V will harm the USB-6215 as its overvoltage protection is +-20 V for the counter's Digital I/O pins.

There are two possible solutions to this:
  1. The USB-6215 interprets an input signal between 0 V and 0.8 V as "low" and between 2 V and 5.25 V as "high". The output signals of the above-mentioned Flow Meter are square waves with 0 V as low and 23 V as high. This signal can be decreased to a high value between 2 V and 5.25 V using a simple voltage divider.
  2. Many standard flow meters work with supply voltages between 10 V and 28 V. Using a 10 V DC power adapter instead of a 24 V one would decrease the voltage into a safer range. A voltage divider can then lower the signal to the desired value. Omitting the voltage divider and feeding the USB-6215's digital inputs 10 V will put the respective inputs into the overvoltage state.

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