How to calculate the derivative of an array using measurement studio?

[nunzio]

Hi I am using a counter task to read the position from a rotary encoder. I would like to calculate the angular speed (let's not consider here all the constants like Pi etc). Using the differentiate function  (NationalInstruments.Analysis.Dsp.SignalProcessing.Differentiate) i obtain a result that is clearly uncorrect (e.g. when the encoder stops the value doesn't go to 0 but remains constant). What am I doing wrong? I attach a few lines of code

Imports NationalInstruments.Analysis.Dsp.SignalProcessing
(...)
'this is the position vector
contatore = myCICounterReader.ReadMultiSampleDouble(SamplesToRead)
'this should be the speed vector
velocita = Differentiate(contatore,SamplingInterval, 0, 0)

tkx
nunzio

[Chuck_81]

Hello Nunzio,

sorry for the late reply. Have you verified that the data included into contatore array are the ones you're expecting so the velocita array will contain zero values? The function call

Differentiate(contatore,SamplingInterval, 0, 0)

seems correct, try to replace contatore input with a known array and then check if everything works correctly.

Best regards,

Fabio