Table Of Contents

IviScope Fetch Waveform Measurement [WM] (G Dataflow)

Version:
    Last Modified: October 24, 2017

    Fetches a waveform measurement from the channel you specify.

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    measurement function

    Pass the waveform measurement you want the oscilloscope to perform.

    Defined Values

    IVISCOPE_VAL_FALL_TIME Rise Time - The length of time for the first rising edge of the signal to rise from the low reference level to the high reference level.
    IVISCOPE_VAL_FALL_TIME Fall Time - The length of time for the first falling edge of the signal to fall from the high reference level to the low reference level.
    IVISCOPE_VAL_FREQUENCY Frequency - The frequency of one complete cycle in the waveform.
    IVISCOPE_VAL_PERIOD Period - The length of time of one complete cycle in the waveform.
    IVISCOPE_VAL_VOLTAGE_RMS Voltage RMS - The true Root Mean Square voltage of the entire waveform.
    IVISCOPE_VAL_VOLTAGE_CYCLE_RMS Voltage RMS (Cycle) - The true Root Mean Square voltage over the first cycle in the waveform.
    IVISCOPE_VAL_VOLTAGE_MAX Voltage Max - The maximum amplitude found in the entire waveform.
    IVISCOPE_VAL_VOLTAGE_MIN Voltage Min - The minimum amplitude found in the entire waveform.
    IVISCOPE_VAL_VOLTAGE_PEAK_TO_PEAK Voltage Vpp - The absolute difference between the Voltage Max and the Voltage Min.
    IVISCOPE_VAL_VOLTAGE_HIGH Voltage High - The voltage that corresponds to 100% when you use the reference levels. The oscilloscope calculates this value using either the min/max or histogram methods. The min/max method uses the maximum value found. The histogram method uses the most common value found above the middle of the waveform.
    IVISCOPE_VAL_VOLTAGE_LOW Voltage Low - The voltage that corresponds to 0% when you use the reference levels. The oscilloscope calculates this value using either the min/max or histogram methods. The min/max method uses the minimum value found. The histogram method uses the most common value found below the middle of the waveform.
    IVISCOPE_VAL_VOLTAGE_AVERAGE Voltage Avg. - The arithmetic average amplitude of the entire waveform.
    IVISCOPE_VAL_WIDTH_NEG Width Negative - The length of time between the mid reference level points of the first negative pulse in the waveform.
    IVISCOPE_VAL_WIDTH_POS Width Positive - The length of time between the mid reference level points of the first positive pulse in the waveform.
    IVISCOPE_VAL_AMPLITUDE Amplitude - The Voltage High less the Voltage Low in Volts over the entire waveform.
    IVISCOPE_VAL_OVERSHOOT Overshoot - The relative waveform distortion which follows an edge transition. It is calculated using the following formula: - for the rising edge: OVERSHOOT = ((local maximum - Voltage High)/Amplitude)*100% where the local maximum is the maximum voltage of the signal in the first half of the time period that commences when the rising edge crosses the high reference level and concludes when the subsequent falling edge crosses the high reference level.

    For the rising edge: OVERSHOOT = ((local maximum - Voltage High)/Amplitude)*100% where the local maximum is the maximum voltage of the signal in the first half of the time period that commences when the rising edge crosses the high reference level and concludes when the subsequent falling edge crosses the high reference level.

    For the falling edge: OVERSHOOT = ((Voltage Low - local minimum)/Amplitude)*100% where the local minimum is the minimum value of the signal measured in the first half of the time period that commences when the falling edge crosses the low reference level and concludes when the subsequent rising edge crosses the low reference level. The instrument makes the measurement on the edge closest to the beginning of the waveform record.

    Configuring Reference Levels

    You must configure the appropriate reference levels before you call this function. You configure the low, mid, and high references either by calling the IviScope Configure Reference Levels Node or by setting the following properties: IviScope>>Waveform Measurement>>Measurement High Reference [WM] IviScope>>Waveform Measurement>>Measurement Low Reference [WM] IviScope>>Waveform Measurement>>Measurement Mid Reference [WM].

    Default: IVISCOPE_VAL_RISE_TIME

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    measurement

    Returns the measured value. Units: The units depend on the Measurement Function you select.

    Measurement Functions

    Rise Time seconds
    Fall Time seconds
    Frequency hertz
    Period seconds
    Voltage RMS volts
    Voltage RMS (Cycle) volts
    Voltage Max volts
    Voltage Min volts
    Voltage Vpp volts
    Voltage High volts
    Voltage Low volts
    Voltage Avg. volts
    Voltage Avg. (Cycle) volts
    Width Negative seconds
    Width Positive seconds
    Duty Cycle Negative percent
    Duty Cycle Positive percent
    Amplitude volts
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    channel name

    String you pass to represent the virtual channel name that you assign to the instrument in the Configuration Utility from which you want to read the minimum and maximum waveforms. This control accepts virtual channel names you have assigned to the specific instrument you are using. It also accepts the instrument-specific channel names.

    Achieving Interchangeability

    Virtual Channel Names

    The virtual channel name should be sufficiently specific to the test system such that it is unlikely to conflict with a physical channel name. Virtual channel names are aliases for instrument-specific channel strings. The instrument-specific channel strings can differ from one instrument to another. Virtual channel names allow you to use and swap instruments without having to change the channel names in your source code. You assign a virtual channel name to an instrument-specific channel through the Configuration Utility.

    Default: "CHANNEL1"

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    instrument handle out

    The instrument handle that you obtain from the IviScope Initialize or IviScope Initialize With Options node. The handle identifies a particular instrument session.

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    instrument handle

    The instrument handle that you obtain from the IviScope Initialize or IviScope Initialize With Options node. The handle identifies a particular instrument session.

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    error out

    Error information.

    The node produces this output according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.
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    error in

    Error conditions that occur before this node runs.

    The node responds to this input according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Default: No error

    Channel Not Enabled Error

    If the channel is not enabled for the acquisition, this function returns the IVISCOPE_ERROR_CHANNEL_NOT_ENABLED (0xBFFA2001) error.

    Invalid Acquisition Type Error

    This node fetches waveforms when you set the acquisition type to IVISCOPE_VAL_PEAK_DETECT or IVISCOPE_VAL_ENVELOPE. If the acquisition type is not one of the listed types, the node returns the IVISCOPE_ERROR_INVALID_ACQ_TYPE (0xBFFA2004) error.

    Obtaining Min/Max Waveforms

    The waveforms are from an acquisition that you previously initiated. Use the IviScope Initiate Acquisition Node to start an acquisition on the channels that you enable with the IviScope Configure Channel Node. The oscilloscope acquires the min/max waveforms for the enabled channels concurrently. You use the IviScope Acquisition Status Node to determine when the acquisition is complete. You must call this node separately for each enabled channel to obtain the min/max waveforms.

    You can call the IviScope Read Min Max Waveform [MmW] Node instead of the IviScope Initiate Acquisition Node. The IviScope Read Min Max Waveform [MmW] Node starts an acquisition on all enabled channels, waits for the acquisition to complete, and returns the min/max waveforms for the channel you specify. You call this node to obtain the min/max waveforms for each of the remaining channels.

    Configuring Reference Levels

    You must configure the appropriate reference levels before you call this node. You configure the low, mid, and high references either by calling the IviScope Configure Reference Levels [WM] Node or by setting the following properties.

    IviScope>>Waveform Measurement [WM]>> Measurement High Reference [WM]

    IviScope>>Waveform Measurement [WM]>> Measurement Low Reference [WM]

    IviScope>>Waveform Measurement [WM]>> Measurement Mid Reference [WM]

    Checking Instrument Status

    This node does not check the instrument status. Typically, you call this node only in a sequence of calls to other low-level driver nodes. The sequence performs one operation. You use the low-level nodes to optimize one or more aspects of interaction with the instrument. If you want to check the instrument status, call the IviScope Error-Query Node at the conclusion of the sequence.

    Simulated Waveforms

    The class driver returns a simulated minimum and maximum waveform when this node is called and the IviScope>>Inherent IVI Settings>>User Options>>Simulate property is set to TRUE and the IviScope>>Inherent IVI Settings>>User Options>>Use Specific Simulation property is set to FALSE. For information on how to configure a simulated waveform, refer to the online help manual.

    Extension Group

    This node is part of the IviScopeWaveformMeasurement [WM] extension group.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: Not supported

    Web Server: Not supported in VIs that run in a web application


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