03-26-2017 05:20 AM
i am so puzzled !
i used butterworth coefficient vi get the fs=8000hz,low frequency 500hz filter coefficient and used in labview vi ,put 50hz sine wave in ,i dont know why the siginal changed sososo much amplitiude ?i just put a pure wave in the filter no noise no other frequency wave !please help me!i think the labview makes me so puzzled!
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03-26-2017 06:41 AM
03-26-2017 07:03 AM
lowpass filter dont need higher cutoff frequency
03-26-2017 07:11 AM
03-27-2017 03:19 AM
I'm not sure why, but try using the "IIR Cascade Filter.vi" instead of the "IIR Filter.vi".
Or use the Butterworth Filter.vi which combines the coefficient and actual filter VIs.
03-27-2017 07:11 AM
@dan_u wrote:
I'm not sure why, but try using the "IIR Cascade Filter.vi" instead of the "IIR Filter.vi".
Or use the Butterworth Filter.vi which combines the coefficient and actual filter VIs.
dan_u is correct. Use the IIR Cascade Filter.vi
03-27-2017 01:32 PM
The IIR filter.vi requires coefficients in direct form.
So, in your original code, we should convert the coefficients to direct form VI before passing it to the IIR filter.vi.
03-30-2017 07:15 AM