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IviDigitizer Fetch Waveform Real64 (G Dataflow)

Version:
    Last Modified: October 24, 2017

    This node returns the waveform the digitizer acquired for the specified channel. The waveform is from a previously initiated acquisition. Notes: (1) You use the IviDigitizer Initiate Acquisition Node to start an acquisition on the channels that the end-user configures with the IviDigitizer Configure Channel Node. The digitizer acquires waveforms on the concurrently enabled channels. If the channel is not enabled for the acquisition, this node returns the Channel Not Enabled error. (2) You can use the IviDigitizer Acquisition Status Node to determine when the acquisition is complete. You must call the IviDigitizer Fetch Waveform Real64 Node separately for each enabled channel to obtain the waveforms. Alternatively, you can use the IviDigitizer Wait For Acquisition Complete Node to block the calling program until the acquisition is finished. (3) You can call the IviDigitizer Read Waveform Real64 Node instead of the IviDigitizer Initiate Acquisition Node. The IviDigitizer Read Waveform Real64 Node starts an acquisition on all enabled channels, waits for the acquisition to complete, and returns the waveform (as well as various waveform parameters) for the specified channel. You call this node to obtain the waveforms for each of the remaining channels. (4) After completion each element in the Waveform Array parameter is the actual sampled voltage in Volts. (5) This node does not check the instrument status. Typically, the end-user calls this node only in a sequence of calls to other low-level driver nodes. The sequence performs one operation. The end-user uses the low-level nodes to optimize one or more aspects of interaction with the instrument. Call the IviDigitizer Error Query Node at the conclusion of the sequence to check the instrument status. (6) The data type of the returned waveform array is ViReal64.

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    Initial X Time Seconds

    Specifies the seconds portion of the absolute time at which the first data point was acquired. Note that the actual time is the sum of Initial X Time Seconds and Initial X Time Fraction. The time is specified as the sum of two values because a single double-precision floating-point number does not have sufficient range and resolution to specify the time.

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    Initial X Offset

    The time in relation to the Trigger Event of the first point in the waveform in seconds. Negative values mean that the first point in the waveform array was acquired before the trigger event.

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    Initial X Time Fraction

    Specifies the fractional portion of the absolute time at which the first data point was acquired. Note that the actual time is the sum of Initial X Time Seconds and Initial X Time Fraction. The time is specified as the sum of two values because a single double-precision floating-point number does not have sufficient range and resolution to specify the time.

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    Waveform Array

    Buffer into which the acquired waveform is stored. Notes: This array is always user allocated, and it must contain at least as many elements as the value you specify with the Number of Points parameter.

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    Actual Points

    Indicates how many data points were actually retrieved from the instrument.

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    First Valid Point

    Indicates the index of the first valid data point in the output Data array. This value will often be zero. However, some digitizer hardware designs transfer data most efficiently when the data is aligned with specific memory address boundaries. In those cases, the hardware may return a few invalid data points at the beginning of a record. This eliminates the need to shift the data during the transfer, ensuring maximum data transfer rates.

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    X Increment

    The time between points in the acquired waveform in seconds.

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    Waveform Array Size (256)

    Specifies the allocated size of the WaveformArray buffer, in number of data points. If this value is smaller than the total number of points to be retrieved, the driver will fill the waveform buffer as fully as possible and return the actual number of points retrieved in the Actual Points parameter. Default Value: 256

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    Channel Name ("")

    Specifies the name of the channel from which to retrieve the data. Users who want to achieve interchangeability should use a virtual channel name. The virtual channel name should be sufficiently specific to the test system such that it is unlikely to conflict with a physical channel name. Default Value: "" Note: You can specify the trace name as a string variable or as a literal enclosed in double quotes.

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    instrument handle out

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

    Default: None

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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

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    instrument handle

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

    Default: None

    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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