niDCPower_GetAttributeViReal64

NI-DCPower Function Reference

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niDCPower_GetAttributeViReal64

ViStatus niDCPower_GetAttributeViReal64(ViSession vi, ViConstString channelName, ViAttr attribute, ViReal64 *value)

Purpose

Queries the value of a ViReal64 attribute.

You can use this function to get the values of device-specific attributes and inherent IVI attributes. If the attribute represents a device state, this function performs device I/O in the following cases:

  • State caching is disabled for the entire session or for the particular attribute.
  • State caching is enabled and the currently cached value is invalid.

Parameters

Input
Name Type Description
vi ViSession Identifies a particular instrument session. vi is obtained from the niDCPower_init or niDCPower_InitWithOptions function.
channelName ViConstString If the attribute is channel-based, this attribute specifies the name of the channel on which to set the value of the attribute. If the attribute is not channel-based, then pass VI_NULL or an empty string. Valid channel names are 0, 1, and 2.
attribute ViAttr Specifies the ID of an attribute. From the function panel window, you can use this control as follows.
  • In the function panel window, click on the control or press Enter or the spacebar to display a dialog box containing hierarchical list of the available attributes. Help text is shown for each attribute. Select an attribute by double-clicking on it or by selecting it and then pressing Enter.
  • A ring control at the top of the dialog box allows you to see all IVI attributes or only the attributes of type ViReal64. If you choose to see all IVI attributes, the data types appear to the right of the attribute names in the list box. Attributes with data types other than ViReal64 are dim. If you select an attribute data type that is dim, LabWindows/CVI transfers you to the function panel for the corresponding function that is consistent with the data type.
  • If you want to enter a variable name, press Ctrl+T to change this ring control to a manual input box. If the attribute in this ring control has named constants as valid values, you can view the constants by moving to the value control and pressing Enter.
Output
Name Type Description
value ViReal64* Returns the current value of the attribute. Passes the address of a ViReal64 variable.

If the attribute currently showing in the attribute ring control has constants as valid values, you can view a list of the constants by pressing Enter on this control. Select a value by double-clicking on it or by selecting it and then pressing Enter.

Return Value

Name Type Description
StatusViStatusReports the status of this operation. To obtain a text description of the status code, call the niDCPower_error_message function. To obtain additional information concerning the error condition, call the niDCPower_GetError function.
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