displacement data filtering

[pomplamoose]

Hello, dear fellows! I am facing a problem as a novice in data acquisition: there is a test rig which consists of, apart from everything else, two displacement sensors, which acquire data of the rotor displacement over time. the data i am recieving is noisy, so i had to filter it. i use butterworth topology of a filter and for a start default settings of high cutoff and low cutoff frequencies. it is a bandstop filter since i checked the signal in frequency domain and found out the bandwidth of noise. a few words on it: there is a metal cyllinder i use to test the sensors. so when i dont move the object, the sensor shows a straight line, which means the signal i need has 0 frequency. that means that any other change in frequency domain would indicate the frequency of noise. i found out it is between apprx 4000 and 4250. but no matter how i tried the signal would not get filtered. the fact is when i send non-dynamic data (orange line lol) to the waveform out of the filter it shows ok but the signal doesnt change over real time. so i built a waveform considering the characteristics such as t0, dt of an initial waveform, but after that i recieve an even more noisy data. it might be ive been trying to solve the problem for too long i stuck at some obvious point, but i no longer have any ideas, so any help would be appreciated. thanks a lot!

[Henrik_Volkers]

Reading the help of the filter vi (I added a quick mod of your vi:

[...]

init/cont controls the initialization of the internal states. The default is FALSE. The first time this VI runs or if init/cont is FALSE, LabVIEW initializes the internal states to 0. If init/cont is TRUE, LabVIEW initializes the internal states to the final states from the previous call to this instance of this VI. To process a large data sequence that consists of smaller blocks, set this input to FALSE for the first block and to TRUE for continuous filtering of all remaining blocks.

[pomplamoose]

Henrik, thanks for your reply, could you if possible save the .vi so that i could open it with my version of labview which is 2011? 

[Henrik_Volkers]

On monday ....

Have a nice weekend 🙂

or think about what I wrote, RTFM isn't that hard 😉

[pomplamoose]

Okay, sure.

im okay with manuals, but it comes to reading manuals when nothing else works haha 🙂 actually im better at understanding when i see a wrong and a right 🙂 thanks a lot!

[pomplamoose]

Hope you did not forget haha 🙂

[johnsold]

Here is the relevant portion of the change: Connect Not Equal to Zero? to the init/cont input of the filter.

Lynn

 

[Henrik_Volkers]

thanks johnsold for jumping in 🙂

Sorry , I'm currently at a congress (Capetown :D) and have no access to my LabVIEW stuff. And yes, I forgot about it due to all this stuff that needs to be ready before this trip.

[Henrik_Volkers · Accepted solution]

here we go...

[pomplamoose]

Thanks a lot for your help, Henrik! Cheers!