Filter Express Problem

[Khallood]

Hi all ,
iam using the filter express VI under LabVIEW 8.0 to delete the 50Hz frequency from the signal iam acquiring
but the filter never worked for me , and the attached picture show the signal iam trying to delete and the expected signal
after filtering , the same 😞

can anybody help ?

Message Edited by Khallood on 04-07-2007 10:17 AM

[Khallood]

plz , can any one help me ???

[Conseils]

I think that you have stale data on the display.

Try the attached sample by running it, change the frequency and look at the graph each time!

I think this should help you visualise what's happening.

LabView 8.0 50Hz notch filter sample.

[Khallood]

mmmmmmmmmmmmmm ,,,
thank you very much for ur response ,
i saw the example u attached ,
in my project getting the data from the serial port through VISA
The read function , the filter and the display are placed in timed loop
so i don't think it is a stale data
what should i do in this case ???!!!!

[Khallood]

i forgot to tell , that the visa give string
i used a conversion element to convert it into
byte , then another conversion element to convert
to dynamic data , does it afeect ??!!

and thanks again

[Conseils]

Well, by exclusion.... as we have demonstrated that the filter works, then there is only one place left to look.

Treatment of data its self won't affect the filter function. BUT if the treatment is not correct, then what you will see as a result will be rubbish. So you may think the filter is not working because the input to the filter is not as planned.

Divide and conquer, by isolating various sub elements of your code. Provide test data and verify the results. A good way of doing this is to create sub VI's. You can set the default input to a sub VI as test data and thus verify basic operation of the sub VI before its included in the higher level code.

[DuffmanSays]

I think this is definitely the correct approach – break down the problem into its components to locate the source of the problem. To aid in this process, you may try using some of the spectral measurement VIs to analyze the signal that you are reading from your serial port. From your screenshot, it looks as if the peaks of the waveform are slightly clipped. This may be adding different frequency components than what you expect. You might also try widening the range of your filer to see if there is any effect of a larger stop band. Please post back when you've had a chance to give this a try! Thanks,

Mike D.

[DSPGuy]

Have you checked the dt value of the waveform that is being fed into the filter express vi?  From your original post the graph image timescale seems wrong if that is a 50Hz signal.  After reading the data from the serial port how do you set the dt value?  It should be 1/Fs, where Fs is the sample rate.

[Khallood]

thank you all for ur response ,
am very sorry for the delay
it worked at last , i divided the diagram into blocks , tested each one
many many errors came to the surface ,
it is working now , and i will defend my project next week
plz wesh me good luck


thanxx again

[marp84]

how about this erro, can u tell me how to fix it?