topic Taking the derivative of measured data? in LabVIEW
https://forums.ni.com/t5/LabVIEW/Taking-the-derivative-of-measured-data/m-p/3338412#M980188
<P>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.</P><P><IMG src="https://forums.ni.com/t5/image/serverpage/image-id/187981iD435CDE2227AACDD/image-size/original?v=v2&px=-1" border="0" alt="Speed problem.png" title="Speed problem.png" /></P><P>If any one would like to look at my VI file and help me smooth out my speed graph that would great.<BR /><BR />Thanks</P><P>Ryan</P>Tue, 23 Aug 2016 19:37:30 GMTRyanKlimowski2016-08-23T19:37:30ZTaking the derivative of measured data?
https://forums.ni.com/t5/LabVIEW/Taking-the-derivative-of-measured-data/m-p/3338412#M980188
<P>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.</P><P><IMG src="https://forums.ni.com/t5/image/serverpage/image-id/187981iD435CDE2227AACDD/image-size/original?v=v2&px=-1" border="0" alt="Speed problem.png" title="Speed problem.png" /></P><P>If any one would like to look at my VI file and help me smooth out my speed graph that would great.<BR /><BR />Thanks</P><P>Ryan</P>Tue, 23 Aug 2016 19:37:30 GMThttps://forums.ni.com/t5/LabVIEW/Taking-the-derivative-of-measured-data/m-p/3338412#M980188RyanKlimowski2016-08-23T19:37:30ZRe: Taking the derivative of measured data?
https://forums.ni.com/t5/LabVIEW/Taking-the-derivative-of-measured-data/m-p/3338419#M980192
<P>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.</P><P> </P><P>Just my 2 cents,</P><P> </P><P>Ben</P>Tue, 23 Aug 2016 20:03:08 GMThttps://forums.ni.com/t5/LabVIEW/Taking-the-derivative-of-measured-data/m-p/3338419#M980192Ben2016-08-23T20:03:08ZRe: Taking the derivative of measured data?
https://forums.ni.com/t5/LabVIEW/Taking-the-derivative-of-measured-data/m-p/3338448#M980203
<P>The derivative of a step is an impulse. So the result looks reasonable to me (without looking at the VI).</P><P> </P><P>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.</P><P> </P><P>Lynn</P>Tue, 23 Aug 2016 20:55:03 GMThttps://forums.ni.com/t5/LabVIEW/Taking-the-derivative-of-measured-data/m-p/3338448#M980203johnsold2016-08-23T20:55:03ZRe: Taking the derivative of measured data?
https://forums.ni.com/t5/LabVIEW/Taking-the-derivative-of-measured-data/m-p/3351401#M985094
<BLOCKQUOTE><HR /><LI-USER uid="9539"></LI-USER> wrote:<BR /><P>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.</P><P> </P><P>Just my 2 cents,</P><P> </P><P>Ben</P><HR /></BLOCKQUOTE><P>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? </P><P>Thank you</P>Tue, 27 Sep 2016 06:10:02 GMThttps://forums.ni.com/t5/LabVIEW/Taking-the-derivative-of-measured-data/m-p/3351401#M985094Lysandros2016-09-27T06:10:02Z