Using Attributes and Properties with NI-DMM
NI-DMM contains high-level functions and VIs that set most of the instrument attributes. Use the high-level driver functions and VIs as much as possible, because they handle order dependencies and multithread locking for you.
Some attributes and properties are not accessible through the high-level functions or VIs. For example, Input Resistance is not set with any of the NI-DMM configuration functions or VIs. The values for these attributes and properties must be set using the attribute or property.
Accessing Attributes and Properties
In LabVIEW, properties are accessed through the NI-DMM property node. To access them, complete the following steps:
- Open a VI.
- Make sure that you are viewing the block diagram. Navigate to the NI-DMM palette at Instrument I/O»Instrument Drivers»NI-DMM, and drag the property node icon to the diagram.
- Select the correct property node class by wiring an instrument handle in into the property node reference, or by right-clicking on the property node and choosing Select Class»IVI»niDMM.
- Left-click the property node, and select the property you want to use.
- To add additional properties, resize the property node.
In C and Visual Basic, attributes are accessed with the Get Attribute and Set Attribute functions. These functions correspond to a particular data type. To set the NIDMM_ATTR_INPUT_RESISTANCE attribute, use the niDMM_SetAttributeViReal64 function.
The defined properties values are not always equivalent to the values used in LabVIEW enumeration controls. In NI-DMM VIs, the first value for LabVIEW enumerations always begins at zero. For example, If you use niDMM Config Measurement to set the VI to DC volts, this value is zero. This value is translated before being passed to the driver. If you use the property node to configure the VI, DC volts is set with IVIDMM VAL DC VOLTS = 1.
To translate between LabVIEW enumerated values and IVI constants, use the conversion VIs in LabVIEW located in the NI-DMM.llb.
Refer to the LabVIEW VI Reference or Function Reference for a complete listing of available attributes.