differentiating single end connection lvdt dynamic data usb6008

[touheed]

hello NI forums

i am using an lvdt to measure the displacement of the damper using usb6008 and voltage RSE channel data which is dynamic data is giving me the displacemt information against time and i want to convert this to velocity so that i can have velocity of damper compression.

[NabilahF]

Hi Touheed,

I am an Applications Engineer at National Instruments. Could you please clarify what you mean by lvdt? Also, where are you being able to view the displacement information?

NabilahF

[Henrik_Volkers]

First: What is your question/problem?

2.: It would be helpful to provide the vi you use to capture the data, and also provide some measured data.

LVDT 

I assume your LVDT is already providing a displacement propotional voltage output? 

[touheed]

thanks for your reply 
by lvdt i mean linear variable differential transformer  and the output voltage corrosponds to centimeter data. i am getting exact distance data i want to get the stable velocity signal in m/s units. when i used the time domain differentiation function iam getting unstable velocity signal

[Henrik_Volkers · Accepted solution]

Please replace the chart with a graph (and increase the number of samples), run it once and  do a 'edit_make current values default' , save the vi with the data and post it.

Due to noise the derivate looks even more noisy (a multiplication with 2*Pi*f in the frequency domain), common problem solver: filter 🙂

here I posted a Savitzky-Golay filter that do both: filter the signal and derivate ( as a quick shot: try 20 sidepoints, 3 order, 1 diff)

Important boundary information (condition): What frequency range do you want to cover? 

[touheed]

thank you Henrik it really works but iam not sure i used it as u said. please check my vi whether velocity signal represents correct velocity value of actual displacement signal.

frequrncy to coverwill be at the max 8hz or 10hz not more than that.

once again thanks for the support 

[Henrik_Volkers]

You used the S-G filter , but not the S-G diff filter vi I posted in my link.

Please capture a typical dataset, convert that *CENSORED*  dynamic data into a waveform,  display it in a graph and save that as explaine before.