You are here: NI Home > Support > Product Reference > Manuals > LabVIEW 8.5 Help

Generates a digital Butterworth filter by calling the Butterworth Coefficients VI.

This VI is similar to the Butterworth Filter VI.

Details  Example

	initialize, when TRUE, initializes the internal state of the VI.
	filter type specifies the passband of the filter. 0 Lowpass 1 Highpass 2 Bandpass 3 Bandstop
	x is the input signal to filter.
	sampling freq: fs is the sampling frequency and must be greater than 0. The default is 1.0. If sampling freq: fs is less than or equal to 0, this VI sets Filtered x to 0 and returns an error.
	high cutoff freq: fh is the high cutoff frequency. The default is 0.45. The VI ignores this parameter when filter type is 0 (Lowpass) or 1 (Highpass). When filter type is 2 (Bandpass) or 3 (Bandstop), high cutoff freq: fh must be greater than low cutoff freq: fl and observe the Nyquist criterion.
	low cutoff freq: fl is the low cutoff frequency and must observe the Nyquist criterion. The default is 0.125. If low cutoff freq: fl is less than or equal to 0 or greater than half the value of sampling freq: fs, the VI sets Filtered x to 0 and returns an error. When filter type is 2 (Bandpass) or 3 (Bandstop), low cutoff freq: fl must be less than high cutoff freq: fh.
	order specifies the filter order and must be greater than 0. The default is 2. If order is less than or equal to 0, the VI sets Filtered x to 0 and returns an error.
	Filtered x contains the result of filtering the input sequence x by convolution.
	error returns any error or warning from the VI. You can wire error to the Error Cluster From Error Code VI to convert the error code or warning into an error cluster.

Butterworth Filter PtByPt Details

The values for high cutoff freq: fh and low cutoff freq: fl must observe the following relationship:

0 < f₁ < f₂ < 0.5f_s

where f₁ is low cutoff freq: fl, f₂ is high cutoff freq: fh, and f_s is sampling freq: fs.

Example

Refer to the PtByPt and Array Based Filter VI in the labview\examples\ptbypt\PtByPt_No_HW.llb for an example of using the Butterworth Filter PtByPt VI.