Turn on suggestions

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page

08-23-2016 02:37 PM

Options

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report to a Moderator

Hey I've been trying to take the derivative of some measured data from a digital rotary motion sensor but I'm having a few problems. It would seem since there are so many data points there are alot of areas on my Distance graph are flat for a very brief period of time making the derivative very small. Which I'm assuming is why the graph looks like this.

If any one would like to look at my VI file and help me smooth out my speed graph that would great.

Thanks

Ryan

08-23-2016 03:03 PM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report to a Moderator

It looks like you are doing software timed data acquistion so the variation you are seing maybe more a measurement of the Jitter than the singal itself.

Just my 2 cents,

Ben

Retired Senior Automation Systems Architect with Data Science Automation LabVIEW Champion Knight of NI and Prepper LinkedIn Profile YouTube Channel

08-23-2016 03:55 PM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report to a Moderator

The derivative of a step is an impulse. So the result looks reasonable to me (without looking at the VI).

One good way to get a derivative of noisy data is to use the Savitsky-Golay filter method. Depending on whihc version of LV you have, the details vary because NI has made changes in the implementations of the S_G filters.

Lynn

09-27-2016 01:10 AM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report to a Moderator

@Ben wrote:It looks like you are doing software timed data acquistion so the variation you are seing maybe more a measurement of the Jitter than the singal itself.

Just my 2 cents,

Ben

Ben, I was searching for derivatives on labview in the forum and bumped on your comment. When you say "software timed acquisition" do you mean that the A/D converter is triggered by the computer clock in order to acquired data? Is it possible to use hardware timed acquisition for a usb device like the NI-6211?

Thank you