Table Of Contents

Amplitude Measurements (Cycle Average and RMS) (G Dataflow)

Version:
    Last Modified: January 9, 2017

    Returns the average and RMS levels of a specific cycle of a periodic signal.

    connector_pane_image
    datatype_icon

    cycle number

    Cycle, or period, of the periodic signal on which to perform the measurement.

    datatype_icon

    signal

    The input signal.

    This input can be a waveform or an array of waveforms.

    Each waveform is required to contain at least a specific number of complete cycles defined by cycle number, where a cycle is defined as the interval between two consecutive rising middle reference level crossings.

    datatype_icon

    reference levels settings

    High, middle, and low reference levels of a waveform.

    datatype_icon

    high ref level

    High reference level of the waveform.

    After the signal crosses the mid ref level in the rising direction, it must cross the high ref level before the next falling mid ref level crossing can be counted.

    Default: 90

    datatype_icon

    mid ref level

    Middle reference level of the waveform.

    The interval between consecutive rising mid ref level crossings defines one cycle, or period, of the waveform. At least one high or low reference level crossing must separate each mid ref level crossing.

    Default: 50

    datatype_icon

    low ref level

    Low reference level of the waveform.

    After the signal crosses the mid ref level in the falling direction, it must cross the low ref level before the next rising mid ref level crossing can be counted.

    Default: 10

    datatype_icon

    ref units

    Units of the high, middle, and low reference levels.

    Name Value Description
    absolute 0 Interprets the reference levels as absolute levels.
    percent 1 Interprets the reference levels as a percentage of the full range of the waveform.

    Default: percent

    datatype_icon

    error in

    Error conditions that occur before this node runs. The node responds to this input according to standard error behavior.

    Default: No error

    datatype_icon

    state levels settings

    Settings that determine the high and low state levels of a waveform.

    datatype_icon

    method

    Method this node uses to compute the high and low state levels of the waveform.

    Name Description
    histogram Returns the levels of the histogram bins with the maximum number of hits in the upper and lower regions of the waveform. The upper and lower regions of the waveform include the upper and lower 40%, respectively, of the peak-to-peak range of the waveform.
    peak Searches the entire waveform for its maximum and minimum levels.
    auto select Determines whether the histogram bins that correspond to the high and low state levels each have over 5% of the total hits. If so, this node returns those results. Otherwise, this node uses the peak method. This ensures a reasonable answer for either a square wave (ignoring the overshoot and undershoot) or a triangle wave (where a histogram fails).

    Default: auto select

    datatype_icon

    histogram size

    Number of bins in the histogram this node uses to determine the high and low state levels of the waveform.

    If you select the peak method, this node ignores this input.

    Default: 256

    datatype_icon

    histogram method

    Method this node uses to compute the histogram. Currently, mode is the only available histogram method.

    Name Description
    mode Uses the mode method.
    datatype_icon

    reserved

    Value reserved for future use.

    datatype_icon

    cycle average

    Mean level of one complete period of a periodic input waveform.

    Algorithm for Calculating cycle average

    The following equation computes the cycle average:

    average = 1 numPoints i = cycle waveform [ i ]

    where i indicates the waveform samples that fall in the single period specified by cycle number and numPoints is given by the following equation:

    numPoints = int ( period d t + 0.5 )

    where dt is the time between two samples and int() is a function that returns the integer portion of a floating-point number.

    The cycle average of a perfect sine wave is zero, while the average level of the entire waveform can be nonzero due to partial periods at the boundaries of the waveform.

    datatype_icon

    cycle RMS

    Root mean square value of one complete period of a periodic input waveform.

    Algorithm for Calculating cycle RMS

    The following equation computes the RMS value:

    RMS cycle = 1 numPoints i = cycle ( waveform [ i ] ) 2

    where i indicates the waveform samples that fall in the single period specific by cycle number and numPoints is given by the following equation:

    numPoints = int ( period d t + 0.5 )

    where dt is the time between two points and int() is a function that returns the integer portion of a floating-point number.

    datatype_icon

    error out

    Error information. The node produces this output according to standard error behavior.

    datatype_icon

    measurement info

    Measurement cycle interval end points and the absolute reference levels used to define the measurement cycle.

    datatype_icon

    start time

    Time of the rising middle reference level crossing that defines the start of the measurement interval.

    datatype_icon

    end time

    Time of the rising middle reference level crossing that defines the end of the measurement interval

    datatype_icon

    ref levels

    Three user-defined reference levels of the waveform in absolute units.

    datatype_icon

    high ref level

    The high reference level.

    datatype_icon

    mid ref level

    The middle reference level.

    datatype_icon

    low ref level

    The low reference level.

    datatype_icon

    ref units

    Units of the reference levels.

    ref units is always absolute in measurement info.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: Not supported


    Recently Viewed Topics