Table Of Contents

IviScope Read Waveform (G Dataflow)

Last Modified: October 24, 2017

Initiates an acquisition on all channels that you enable with the IviScope Configure Channel Node.

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Use this node to read waveforms when you set the acquisition mode to IVISCOPE_VAL_NORMAL, IVISCOPE_VAL_HI_RES, or IVISCOPE_VAL_AVERAGE. If the acquisition type is not one of the listed types, the node returns the IVISCOPE_ERROR_INVALID_ACQ_TYPE (0xBFFA2004) error.

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After this node executes, each element in the Waveform Array parameter is either a voltage or a value indicating that the oscilloscope could not sample a voltage.

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You configure the interpolation method the oscilloscope uses with the IviScope Is Invalid Waveform Element Node. If you disable interpolation, the oscilloscope does not interpolate points in the waveform. If the oscilloscope cannot sample a value for a point in the waveform, the driver sets the corresponding element in the Waveform Array to an IEEE defined NaN (Not a Number) value and the node returns IVISCOPE_WARN_INVALID_WFM_ELEMENT (0x3FFA2001).

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You can test a waveform value for an invalid value condition by calling the IviScope Is Invalid Waveform Element Node.

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This node performs interchangeability checking when the IviScope>>Inherent IVI Settings>>User Options>>Interchange Check property is set to TRUE. If the IviScope>>Inherent IVI Settings>>User Options>>Spy property is set to TRUE, you use the NI I/O Trace utility to view interchangeability warnings. You use the IviScope Get Next Interchange Warning Node to retrieve interchangeability warnings when the IviScope>>Inherent IVI Settings>>User Options>>Spy property is set to FALSE. For more information about interchangeability checking, refer to the help text for the IviScope>>Inherent IVI Settings>>User Options>>Interchange Check property.

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The class driver returns a simulated 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.

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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 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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waveform array

Returns the waveform that the oscilloscope acquires. Units: volts

Configuring Interpolation

Testing a Waveform Value

You can test a waveform value for an invalid value condition by calling the IviScope Is Invalid Waveform Element node.

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x increment

Indicates the length of time between points in the Waveform Array. Units: seconds

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initial x

Indicates the time of the first point in the Waveform Array. The time is relative to the trigger event. For example, if the oscilloscope acquires the first point in the Waveform Array 1 second before the trigger, this parameter returns the value -1.0. If the acquisition of the first point occurs at the same time as the trigger, this parameter returns the value 0.0. Units: seconds

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maximum time

Value indicating the maximum length of time in which to allow the read waveform operation to complete. Units: milliseconds.

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The Maximum Time parameter applies only to this node. It has no effect on other timeout parameters or properties.

IVISCOPE_ERROR_MAX_TIME_EXCEEDED Error

Defined Values

IVISCOPE_VAL_MAX_TIME_INFINITE (-1)
IVISCOPE_VAL_MAX_TIME_IMMEDIATE (0)

Default: 5000 (ms)

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waveform size

Value representing the expected size of the waveforms that the oscilloscope acquires. That value is greater than or equal to the minimum number of points you specify in the IviScope Configure Acquisition Record Node.

Determining Waveform Size

Default: 1000

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actual points

Indicates the number of points the node places in the Waveform Array parameter.

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channel name ("CHANNEL1")

Specifies the virtual channel name that you assign to the instrument in the Configuration Utility. 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. 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. This control accepts virtual channel names you have assigned to the specific instrument you are using. It also accepts the instrument-specific channel names.

Default: "CHANNEL1"

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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