How to measure angular speed by RVDT

Hello,
I quite new in labVIEW and I am trying to measure angular speed of shaft by RVDT which is able to measure in electrical range 0°-280°. I use NI USB-6008 card and RVDT is also powered by this card (5V). I have already found way how to measure angular position but i do not now how to convert it to angular speed. I tryed to do it by derivation but the result was weird. Could anybody give me an advice how to do that. I would really appreciate that.
My VI is attached.
Attachments:
rot pot.vi ‏154 KB

Hi kome01,
The issue comes from the fact you are only acquiring one sample per iteration of the loop, and to differentiate you need to provide at least two values, as well as a time difference between each.
The Express VI you are using is clever in the way that it can measure the time between samples for you, but you will still need to provide multiple samples. I have changed your VI to continuously acquire samples from the potentiometer, and have provided some notes in the block diagram to help you.
Hope this helps!
Attachments:
rot pot.vi ‏153 KB

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