Filters signals in either single or multiple waveforms. If you are filtering multiple waveforms, the VI maintains separate filter states for each waveform. The data types you wire to the signal in and FIR filter specifications inputs determine the polymorphic instance to use.

Note Do not use the single-channel instance of this VI for continuous multiple-channel processing.


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Inputs/Outputs

  • cbool.png reset filters —

    reset filters forces the filter coefficients to be redesigned and the internal filter states to be reset to zero for each input waveform when it is TRUE.

  • c1dmsdt.png signal(s) in —

    signal(s) in is an array of waveforms containing the signals to filter.

  • cerrcodeclst.png error in (no error) —

    error in describes error conditions that occur before this node runs. This input provides standard error in functionality.

  • c1dnclst.png FIR filter specifications —

    FIR filter specifications is an array of filter specifications. This array must have the same size as the signal(s) in array of waveforms.

  • cenum.png Topology —

    Topology determines the design type of the filter.

    0
    Off
    (default)
    1
    FIR by Specification
    2
    Equi-ripple FIR
    3
    Windowed FIR
  • cenum.png Type —

    Type specifies the passband of the filter according to the following values.

    0
    Lowpass
    1
    Highpass
    2
    Bandpass
    3
    Bandstop
  • ci32.png #Taps —

    #Taps is the number of taps in the FIR filter. The default is 50.

  • cdbl.png Lower PB —

    Lower PB is the lower of the two passband frequencies. The default is 100 Hz.

  • cdbl.png Upper PB —

    Upper PB is the higher of the two passband frequencies. The default is 0.

  • cdbl.png Lower SB —

    Lower SB is the lower of the two stopband frequencies. The default is 200 Hz.

  • cdbl.png Upper SB —

    Upper SB is the higher of the two stopband frequencies. The default is 0.

  • c1dcclst.png optional FIR filter specifications —

    optional FIR filter specifications is an array of optional filter specifications. This array may be empty or must have the same size as the FIR filter specifications array.

  • cdbl.png PB Gain —

    PB Gain is the gain at the passband frequencies. Gain may be specified in linear terms or dB. The default is –3dB.

  • cdbl.png SB Gain —

    SB Gain is the gain at the stopband frequencies. Gain may be specified in linear terms or dB. The default is –60dB.

  • cbool.png Scale —

    Scale determines how the PB Gain and SB Gain parameters are interpreted.

  • cenum.png Window —

    Window controls which smoothing window is applied to the truncated coefficients.

    Smoothing windows decrease ripple in the filter passband and improve the ability of the filter to attenuate frequency components in the filter stopband.

    0
    None
    1
    Hanning
    2
    Hamming
    3
    Triangular
    4
    Blackman
    5
    Exact Blackman
    6
    Blackman-Harris
    7
    Kaiser-Bessel
    8
    Flat Top
  • i1dmsdt.png signal(s) out —

    signal(s) out is an array of signals that have been filtered according to the filter specifications controls.

  • i1dcclst.png filter information —

    filter information is an array of clusters containing information about each of the designed filters.

  • icclst.png magnitude H(w) —

    magnitude H(w) is the magnitude response of the filter. You can wire this cluster to a graph.

  • idbl.png f0 —

    f0 is the start frequency of the magnitude response.

  • idbl.png df —

    df is the spacing between elements of the magnitude response in hertz.

  • i1ddbl.png Mag H(w) —

    Mag H(w) is an array of values containing the magnitude response of the filter.

  • icclst.png phase H(w) —

    phase H(w) is the phase response of the filter.

  • idbl.png f0 —

    f0 is the start frequency of the phase response.

  • idbl.png df —

    df is the spacing between elements of the magnitude response in hertz.

  • i1ddbl.png Phase H(w) —

    Phase H(w) is an array of values containing the phase response of the filter, expressed in degrees.

  • ii32.png order —

    order is the order of the filter.

  • ierrcodeclst.png error out —

    error out contains error information. This output provides standard error out functionality.

    • This VI filters the signal(s) in a waveform array according to the FIR filter specifications and optional FIR filter specifications arrays. If you are filtering multiple waveforms, the VI applies a different filter to each of the input waveforms and maintains a separate filter state for each waveform. The VI uses the optional FIR filter specifications only if Filter topology is FIR by Specification or Windowed FIR. You do not need to wire reset filter. This VI resets itself the first time it is called.

    The Digital FIR Filter VI can perform single-channel measurements in both one-shot mode (single call) and continuous mode (multiple calls with history). It can perform multi-channel measurements only in one-shot mode. If you want to make multiple-channel measurements in continuous mode, either use the multichannel instance of this VI or use one instance of this VI per channel.

    The single-channel instance of this VI is intended primarily for continuous processing of a single channel. Do not generalize this behavior to the multi-channel case, typically by using this single-channel VI in a For Loop to continuously process multiple channels by indexing an array of waveforms.

    The single-channel instance of this VI maintains internal state information for a single channel only. Calling this VI to process another channel without clearing the history using the reset filter control results in an unexpected behavior of this VI because the internal state information is passed from one channel to another.

    Examples

    Refer to the following example files included with LabVIEW.

    • labview\examples\Signal Processing\Waveform Conditioning\FIR Filtering and Response.vi
    • labview\examples\Signal Processing\Waveform Conditioning\FIR Filtering Using Optional Specs.vi