Table Of Contents

Fetch (Multi Waveform » 1D Cluster Complex DBL) (G Dataflow)

Last Modified: April 2, 2018

Retrieves the waveform the digitizer has acquired for multiple channels and records.

This function returns a one-dimensional array of complex, scaled waveforms in clusters that include timing information.

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session in

Handle that identifies the NI-SCOPE instrument session as previously allocated by Initialize With Options.

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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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channels

The channel from which to acquire data.

Channel String Syntax

You can input channels with the following options:
  • A single channel, such as 0
  • A list of channels, such as 0,1 or 3,2,1,0.
  • A range of channels, such as 0-7 or 0:7.
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Note  

The order of channels in a list is important. The data for each channel is returned in the order the channels occur in the list.

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numsamples

The maximum number of samples to fetch for each waveform.

This function reads the actual record length and attempts to acquire all available samples. If the function fails to complete within the timeout period, the function returns an error. If the acquisition finishes with fewer points than requested, some devices return partial data if the acquisition finished, was aborted, or a timeout of 0 was used.

Fetching All Available Samples

Use -1 for this parameter if you want to fetch all available samples.

Default: -1

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timeout

The time, in seconds, to wait for the data to be acquired.

Alternate Uses

Use 0 for this parameter to fetch whatever is currently available. Use -1 for this parameter to imply an infinite timeout.

Default: 5

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session out

Reference to the NI-SCOPE instrument session to pass to the next node in the program.

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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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waveform

An array of clusters, each containing the initial time value, time increment, and waveform array. The initial time value in the cluster is the value relative to the trigger. The relative initial time value is the time from the trigger to the first point so the trigger always occurs at time equals zero.

The array of clusters includes waveforms from multiple channels, records, and acquisition types. For example, if the acquisition type is normal, there is one waveform per channel per record. If you call Fetch during a normal acquisition with the channel string "0,1", the order of the output is:

  • record 0, channel 0,
  • record 0, channel 1,
  • record 1, channel 0,
  • record 1, channel 1

The order of the channels is the order specified by channels.

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t0

The initial time value relative to the trigger, such that the trigger always occurs at time equals zero.

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dt

The time interval between two samples in the waveform. This value is 1 / sampling rate for time-domain acquisitions.

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Y

An array of waveform data containing one waveform.

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waveform info

The timing and scaling information about the waveform.

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actualSamples

The actual number of samples in the acquired waveform.

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Note  

The number returned in actualSamples may be less than numSamples if the number you request is not available.

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absoluteInitialX

The timestamp, in seconds, of the first fetched sample. This timestamp is comparable between records and acquisitions; devices that do not support this parameter use 0 for this output.

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relativeInitialX

The time, in seconds, from the trigger to the first sample in the acquired waveform.

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xIncrement

The time, in seconds, between two samples in the acquired waveform.

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offset

The offset factor of the given channel. Use for scaling binary data with the following formula:voltage = binary data x gain factor + offset

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gain

The gain factor of the given channel.Use for scaling binary data with the following formula: voltage = binary data × gain factor + offset.

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reserved1

A reserved value. Do not use.

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reserved2

A reserved value. Do not use.

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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