niDCPower_SetAttributeViReal64

ViStatus niDCPower_SetAttributeViReal64(ViSession vi, ViConstString channelName, ViAttr attribute, ViReal64 value)

Purpose

Sets the value of a ViReal64 attribute.

This is a low-level function that you can use to set 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 or is different than the value you specify.

NI-DCPower contains high-level functions that set most of the device attributes. It is best to use the high-level driver functions as much as possible. They handle order dependencies and multithread locking for you. In addition, they perform status checking only after setting all of the attributes. In contrast, when you set multiple attributes using the SetAttribute functions, this function checks the device status after each call. Also, when state caching is enabled, the high-level functions that configure multiple attributes perform device I/O only for the attributes whose value you change. Thus, you can safely call the high-level functions without the penalty of redundant device I/O.

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. Attributes whose value cannot be set are dim. Help text is shown for each attribute. Select an attribute by double-clicking on it or by selecting it and then pressing Enter. Read-only attributes appear dim in the list box. If you select a read-only attribute, an error message appears. 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.
value	ViReal64	Specifies the value to which you want to set the attribute. 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. Note  Some of the values might not be valid depending upon the current settings of the device session.

Return Value