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Home Support NI Product Manuals NI-VISA 17.0 to 20.0 Manual

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Open (G Dataflow)

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    Last Modified: September 27, 2017

    Opens a session to the device and returns a session identifier that you can use to call any other operations of that device.

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    open timeout

    The maximum time period, in milliseconds, that Open waits before returning an error. This parameter does not set the I/O timeout.

    To specify the timeout used for future operations on the VISA session, use the Timeout property in VISA Properties by selecting General Settings» Timeout Value .

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    resource name

    The resource to be used.

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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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    duplicate session

    A Boolean that specifies whether to open an additional session to a resource even if another session is already open.

    True Opens a new session to the resource even if another session is already open.
    False Connects to the resource using an existing session if one exists. Otherwise, opens a new session.

    A VISA session is a unique logical identifier used by VISA to communicate with a resource. The VISA session is maintained by the resource name parameter and is not seen by the user.

    Default: False

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    access mode

    Setting that specifies how to access the device.

    Name Value Description
    VISA Defaults 0 Opens a session without using an exclusive lock or loading configuration information.
    Exclusive Lock 1 Acquires an exclusive lock immediately upon opening a session. If a lock cannot be acquired, the session is closed and an error is returned.
    Load Configured Settings 4 Configures attributes to values specified by an external configuration utility.
    Load Configured Settings with Exclusive Lock 5 Acquires an exclusive lock immediately upon opening a session and configures attributes to values specified by an external configuration utility.

    Default: VISA Defaults

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    session out

    The resource to which a VISA session is opened.

    This output also includes the class for the session, which matches that of resource name.

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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.

    Opening Multiple VISA Sessions

    If you open a significant number of VISA sessions without closing them, you decrease the available memory resources. Close the session with Close.

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    Note

    This function recognizes all resource strings returned by Find Resource. However, Find Resource does not necessarily return all strings that you can pass to this function.

    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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