simple low pass filter

[Paddy1985]

Yo Guys,

quick question:

I got this sh*t pile of data that I just want to observe quick with a filter. So I don't need an advanced low-pass/high-pass filter in a program. I tried the filter in signal analyses in the plain LabView 7.1 version. But I can't read the array with data and analyze it. I keep on getting the error:

"The following conditions must be met:  0 < f_low <= f_high <= fs/2"

Anyone ideas of building a quick (live) filter into labview to filter the signal and see the results straight away on graphs?

Cheers to all!

[Paddy1985]

this is the VI btw... might be helpfull in looking into what i'm doing...

who can help me out on this one?

[Dennis_Knutson]

In order for the filter to work correctly, you need an input signal (i.e. waveform or dynamic data type) that contains sample rate information. You are not correct in thinking that the merge signal function does this for you. In fact, I think what you are passing to the filter is just the time array and not the signal data at all. From the time array, calculate the dt. Then use the Build Waveform function and wire the dt and Y array to this. Wire the waveform data type to the filter.

[gchristi1]

The simplest low pass filter is just averaging. When I took a digital filter design class, I was facinated by the fact that averaging time is the same as the time for capacitors/inductors to charge/discharge. Just write a vi that does a sliding average.

I'm not a digital guy, so my only experience in this matter is with the grad filter class, so take my advice for what it's worth.

[ayobi]

you can check the value of your fs using the block 'get waveforms components'. wire in your waveform into it and select an output attribute 'dt' . the fs is actually the value of dt. from there then you can determine which cutoff frequence you'r gonna use. choose the fs_high orlow <= than that of dt/2