Using Custom Scales in IEPE Acceleration Tasks in NI MAX

Updated Sep 8, 2020

Reported In

Hardware

  • NI-9219

Programming Language

  • Measurement & Automation Explorer (MAX)

Issue Details

  • I would like to know if when I use custom scales with AI IEPE Acceleration task in NI MAX does the Sensitivity scale and my custom scale get both applied? Or how does it work?

  • I'm quite confused as I believed that they are not both applied to the signal. Apparently, a custom scale supersedes/overrides the “sensitivity” and “sensitivity units” within a Task and I would like to confirm this.

Solution

When creating an Acceleration Task you need to know the specifications of your sensor such as Sensitivity and Iex Value.



When using custom scales the Sensitivity and the Custom Scale, both, are applied.
Take into account that the Sensitivity is not a scale is just a conversion factor.

You can input the Sensitivity factor in a Custom Scale as the Slope, however, take into account that for this to be accurate the Sensitivity should be 1 V/g or 1000mV/g if not the Sensitivity factor and the Custom Scale will be applied affecting the output of your signal.
 



If you would the idea of a Custom Scale is to input the Sensitivity factor as Slope, we recommend you to not use Custom Scales as this will be redundant.

Additional Information

 

  1. IEPE tasks will only accept “custom scale” “pre-scaled” units of “g,” not “volts,” even though the correct input units would be Volts since the scale units are g/V scale.
  • This is statement is correct and expected. An acceleration task (IEPE or not) cannot return Volts, so it cannot use it as the unit. Volts is only the correct unit for a Voltage input task. If you like to use a voltage input, we can enable IEPE excitation programmatically.