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Fetch (Multi Waveform » 1D WDT) (G Dataflow)

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Last Modified: September 15, 2017

Retrieves waveforms the digitizer has acquired from multiple records or multiple channels.

This function returns a one-dimensional array of waveform data types that include timing information.

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session in

Identifies a particular instrument session.

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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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timestamp type

The time basis for the timestamp on the waveform data type data.

Name Value Description
absolute 1 Uses an absolute time basis for the time stamp.
relative 0 Uses a relative time basis for the time stamp.
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session out

Passes the instrument handle to the next node in the program. This parameter has the same value as session in.

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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

A one-dimensional array of waveform data types that contain timing information.

Waveform Order

If you specify a channel list, NI-SCOPE returns the waveforms in the list order. NI-SCOPE returns these records sequentially, so all record 0 waveforms are first. For example, with a two-channel list, you would have the following index values: index 0 = record 0, channel 0 index 1 = record 0, channel 1 index 2 = record 1, channel 0 index 3 = record 1, channel 1
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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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