Is derivative PtByPt same as using a shift register?

[pincpanter]

It turns out that Numerical Recipes in C, 2nd ed. (but not the C++, 3rd ed.) can be found free online: http://www.nr.com/oldverswitcher.html

[JennaU]

Hi justapro,

I also need to find the velocity of a signal in as close to real time as is possible with a non-deterministic operating system.  Have you had any luck with this since you're last post?  I haven't been able to get the Savitzky Golay pt to pt VI to work... so I've been filtering, differentiating (not point to point) and filtering again to get my velocity.  This leaves me with a significant delay.  I think part of my problem with the point to point VIs is that I'm not sure how to initialize them properly.

I'm using LabVIEW 7.1 with a USB 6211 device.

Thanks

Jenna

[justapro]

I could never get much better. The velocity calculation is ok (only one derivative) but the acceleration is garbage. I ended up just working with the velocity. If I need to get a change in velocity I'll probably have to have some delay and use an averaging scheme.

[JennaU]

Thanks for the reply!

I'll let you know if I find a better solution.