NI 6238/6239 Internal Voltage Drop Specification

Updated May 2, 2018

Reported In

Hardware

  • PXI-6238
  • PCI-6238
  • PXI-6239
  • PCI-6239

Issue Details

On the PXI-6238/6239 Device Specifications, I noticed that the internal voltage drop has a specification of 3 V maximum referring to the following figure:

What does the 3 V maximum mean? Can I output a current that would result in an internal voltage drop greater than 3 V without damaging my device?

Solution

The internal voltage drop specification refers to the maximum expected voltage drop relative to the externally supplied voltage. You can set the current output to result in a larger voltage drop without damaging your device. However to ensure that you are able to output the requisite voltage for a desired current output, you will need to supply an external voltage at least 3 V higher than the requisite voltage level. For example if you want to output 7 V (e.g. 10 mA on a 700 Ω load), you will need an external power supply of at least 10 V. 

If you do not supply enough voltage to the Power Supply Pin of your NI 6238/6239, you will not be able to output the desired current level. For example if you tried to output 20 mA to a 1 kΩ load with only a 22 V user-provided power supply, your actual output current will be less than 20 mA. You will need to provide 23V power to ensure 20mA current generation.
 

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