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

Sarah_LAB

Member

08-29-2017 04:10 AM

Options

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

Labels:

Hi,

I try to derive and integral my signal (array 1D of double) but i can't to calculate the **dt** in each case and which gives me as a result this.

this is my diagrame .

derivative -->

Integral -->

How i can to do to adjust correctly the dt for this fuction.

thank you .

Solved! Go to Solution.

GerdW

Knight of NI

08-29-2017 04:20 AM

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

Hi Sarah,

from your images it seems you try to calculate dt from the difference of the first two samples.

Why do you think you get dt when subtracting two sample values? THis would give you just dx…

You should know dt from your signal source. It would help when you would be using the waveform datatype…

Best regards,

GerdW

using LV2011SP1 + LV2017 (+LV2020 sometimes) on Win10+cRIO

GerdW

using LV2011SP1 + LV2017 (+LV2020 sometimes) on Win10+cRIO

08-29-2017 04:25 AM

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

But this is juste an example for this Sinus how i can derivate Random signal for example ?

Is there a method to extract the dt for any signal??

GerdW

Knight of NI

08-29-2017 04:37 AM

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

Hi Sarah,

Is there a method to extract the dt for any signal?

Yes, sure: you ** need to know the signal source** and the sampling rate used at the source!

- When all you got are the sample values "x" then you lost the timing information. Ask the person, who created those signals, for the sample rate.

- Use the waveform datatype in your own VIs as it enforces the use of a proper dt information.

Best regards,

GerdW

using LV2011SP1 + LV2017 (+LV2020 sometimes) on Win10+cRIO

GerdW

using LV2011SP1 + LV2017 (+LV2020 sometimes) on Win10+cRIO

08-29-2017 04:51 AM

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

I understand what you mean, but If we don't know the source, we have just a data signal in array , can not be derived ?

Solution

Accepted by topic author Sarah_LAB

GerdW

Knight of NI

08-29-2017 04:58 AM

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

Hi Sarah,

no.

When this information is gone, then it's really gone…

Best regards,

GerdW

using LV2011SP1 + LV2017 (+LV2020 sometimes) on Win10+cRIO

GerdW

using LV2011SP1 + LV2017 (+LV2020 sometimes) on Win10+cRIO

08-29-2017 05:14 AM

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

What is the dt of this source for example??

Thank youu.

Solution

Accepted by topic author Sarah_LAB

GerdW

Knight of NI

08-29-2017 05:32 AM - edited 08-29-2017 05:33 AM

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

Hi Sarah,

the PtByPt function expects a "time" value at its input - did you read the help for this function?

When you know this time (aka "t") value you can easily calculate dt from it…

(As you should call this function in a loop it would be a good idea to check the loop iteration time. ;))

Best regards,

GerdW

using LV2011SP1 + LV2017 (+LV2020 sometimes) on Win10+cRIO

GerdW

using LV2011SP1 + LV2017 (+LV2020 sometimes) on Win10+cRIO