Derivative on the fly

[Philippe Bruyant]

Hello experts,
I would like to compute on-the-fly the 1st derivative of a curve as it is acquired
at 10Hz with AI Read.VI in a while loop (see attach diagram).
I use Derivative.VI, but it does not work: The derivative is always exactly 0.
Is it because I send one data point at a time?
Any solution/idea/suggestion?
Thank you!
Phil

[rpursley8]

There is a pt-by-pt version of the derivative vi. This one would work.

[Philippe Bruyant]

Thank you Randall
Where can I find the version that would work?

[Donald]

In LV6.1, it's in the following:

Functions>Analyze>Point By Point>Time Domain PtByPy>Derivative x(t) PtByPt

But it is not included in the Base LabVIEW package. Probably the same in LV7.

[suethechemist]

Have a look at the following thread: http://forums.ni.com/ni/board/message?board.id=170&message.id=102065