Subset and Resample (Time Domain)

LabVIEW SignalExpress

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Subset and Resample (Time Domain)

Extracts a subset of an input signal using the Start position and Subset length you specify or resamples an input signal using the time interval (dt) you specify. If you specify a larger dt, Subset and Resample downsamples the signal. If you specify a smaller dt, Subset and Resample upsamples the signal.

ParameterDescription
Input SignalDisplays the input signal.
  • Displayed signal—Specifies the signal(s) to display in the preview graph(s). This option appears only when you select a group of signals for the input.
    Note  If the input signals include scalar values that depend on the values of input waveform signals, you cannot specify to display all signals in the preview graph(s).
Processed SignalDisplays the processed signal.
Input/OutputContains the following options:
  • Input—Contains the following option:
    • Input signal—Specifies the analog waveform for the step.
  • Output—Contains the following options:
    • Export pre-subset signal—Adds the signal that precedes the subset as an output of Subset and Resample.
    • Export post-subset signal—Adds the signal that follows the subset as an output of Subset and Resample.
ConfigurationContains the following options:
  • Subset Setup—Contains the following options:
    • Extract subset—Specifies whether to extract a time subset of the input signal using the Start position and Subset length you specify.
    • Relative time—Specifies if the Start position value is an absolute timestamp value or a time offset relative to the first sample of the input signal.
    • Start position—Specifies the start position of the subset signal.
    • Subset length—Specifies the time span of the subset signal.
  • Resampling Setup—Contains the following options:
    • Resample—Resamples the entire signal or subset you select.
    • Optim. for single record—Optimizes the resampling operation for a single record. If you remove the checkmark from this checkbox, the resampling process assumes that the signals are continuous until you reset the signals.
    • Open interval—Specifies if the subset is an open or closed interval. For example, if an input waveform contains 3 data elements at t={0, dt, 2dt}, an open interval defines the waveform as extending over the time interval 0≤t<2dt, and a closed interval defines the waveform as extending over the time interval 0≤t<3dt. Place a checkmark in this checkbox to specify an open interval.
    • Interpolation type—Contains the following options:
      • Coerce—Sets each output sample value to equal the input sample value that is closest to it in time.
      • Linear—Sets each output sample value to be a linear interpolation between the two input samples that are closest to it in time.
      • Spline—Uses the spline interpolation algorithm to compute the resampled values.
      • Filter based—Uses an interpolation method based on the convolution of the signal with a finite impulse response (FIR) filter.
    • dt—Specifies the time resolution of the resampled time-domain signal. The default is 0.
Filter SetupAvailable when you select Filter based from Interpolation type. Contains the following option:
  • FIR Filter Specification—Contains the following options:
    • Normalized bandwidth—The normalized cut-off frequency of the FIR filter to use. The default is 0.4000.
    • Alias rejection (dB)—The minimum stopband attenuation of the FIR filter to use. The default is 80 dB.
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