What is the difference of the lowpass filter using FIR_Coef with the one using Wind_LPF

[ÐÄÒâÎÞÑÄ]

What is the difference of the designed lowpass filter by FIR_Coef with the
one using Wind_LPF ?

[RajivG]

Hello,

FIR_Coef generates a set of FIR filter coefficients based on the window design method and provides the option to select from the different types of filters. Whereas, Wind_LPF designs a digital lowpass FIR linear phase filter using a windowing technique and provides Five windows.

So there is no difference between the FIR_Coef when using using the "Low Pass Filter" and the Wind_LPF when using the "Rectangular Windows Type". But Wind_LPF provides more options for windows when using LPF, which are not available in FIR_Coef.

I hope it helps,
Rajiv

[Salvio]

hello,

i don't understand how to use this two function. I mean i'm  acquiring a signal from my oscilloscope (it is in my case  a sine[1000]) and i want to filter it to remove all possible noise.
I've seen that the function Wind_LPF has:

this parameters            and           i've choosen this:

sampling frequency:                      1000*50Hz (i'm generating a signal at 50Hz and 10Vpp)
cuttof frequency:                             i think around 60Hz can be good but i have to check it better
number of coeff:                             20 (can be good?)
coefficent array:                              how to set this?  
window tipe:                                    hamming

My problem is that i don't understand how to bring the filtered signal and to put it in the PlotY because i don't see an "output" array  of the function.In what i'm wrong?
Tnx a lot

[Mark_E]

Hi Salvio,

A really great place to get information on how to use each function is the NI LabWindows/CVI Help (e.g. Start » All Programs » National Instruments » LabWindows CVI x.x » LabWindows CVI x.x Help). You can then search for the Wind_LPF page. The output is the coefficientArray which only contains the coefficients for the filter with “numberOfCoef” elements. You then need to use the Convolve function to actually apply the filter to your signal.

An entire example of the code needed to do just this is present in the help file. If you have further questions after exploring it, please repost.

I hope this helps get your filter working!

CVI Analysis Fucntions by Package