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Fetch Waveform Int16

IVI Compliance Package

IviDigitizer Fetch Waveform Int16

IviDigitizerBase Capability Group

This VI returns the waveform the digitizer acquired for the specified channel. The waveform is from a previously initiated acquisition.

Refer to the notes following the input and output descriptions for more information about using this VI.

IviDigitizer Fetch Waveform Int16.vi

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

Default Value: None

cstr Channel Name ("") Specifies the name of the channel from which to retrieve the data.

Default Value: ""

Note:

You can specify the trace name as a string variable or as a literal enclosed in double quotes.

ci64 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

cerrcodeclst error in (no error) The error in cluster can accept error information wired from VIs previously called. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs.

The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed.

idbl 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.

idbl 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.

idbl 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.

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

Default Value: None

i1di16 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 Waveform Array Size parameter.

ii64 Actual Points Indicates how many data points were actually retrieved from the instrument.

ii64 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.

idbl X Increment The time between points in the acquired waveform in seconds.

ierrcodeclst error out The error out cluster passes error or warning information out of a VI to be used by other VIs.

The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed.

idbl Scale Factor Scaling factor for the waveform data.

idbl Scale Offset Scaling offset for the waveform data.

Note Notes  
  • You use the IviDigitizer Initiate Acquisition VI to start an acquisition on the channels that the end-user configures with the IviDigitizer Configure Channel VI. The digitizer acquires waveforms on the concurrently enabled channels. If the channel is not enabled for the acquisition, this VI returns the Channel Not Enabled error.
  • You can use the IviDigitizer Acquisition Status VI to determine when the acquisition is complete. You must call the IviDigitizer Fetch Waveform Int16 VI separately for each enabled channel to obtain the waveforms. Alternatively, you can use the IviDigitizer Wait For Acquisition Complete VI to block the calling program until the acquisition is finished.
  • You can call the IviDigitizer Read Waveform Int16 VI instead of the IviDigitizer Initiate Acquisition VI. The IviDigitizer Read Waveform Int16 VI 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 VI to obtain the waveforms for each of the remaining channels.
  • After this VI executes, each element in the Waveform Array parameter is an unscaled value directly from the digitizer's analog-to-digital converter (ADC).
  • This VI does not check the instrument status. Typically, the end-user calls this VI only in a sequence of calls to other low-level driver VIs. The sequence performs one operation. The end-user uses the low-level VIs to optimize one or more aspects of interaction with the instrument. Call the IviDigitizer Error-Query VI at the conclusion of the sequence to check the instrument status.
  • The data type of the returned waveform array is ViInt16.