Chapter 5
Using the SCXI-1102/B/C
©
National Instruments Corporation
5-15
Using Software for Multiplexed Scanning
Performing scanning operations in software depends on the ADE
you are using. While using LabVIEW or Visual Basic 6, all scanning
operations are prepared in software by using an SCXI
channel string
as the
input to the channel parameter in the analog input VI or function. These
ADEs also support virtual channels using Data Neighborhood (DAQ
Channel Wizard) in MAX. In LabWindows/CVI, C, or C++ development
environments, you need to make several NI-DAQ function calls to set up
each module involved in the scan, the chassis, and the E/M Series DAQ
device controlling the scan.
A discussion describing how to implement multiplexed scanning in the
different ADEs follows. Refer to the ADE manual and the DAQ analog
input examples that come with your application software for more detailed
information on programming the SCXI modules for scanning in
multiplexed mode.
LabVIEW and the SCXI Channel String
For LabVIEW and Visual Basic 6, the channel string determines the
sequence in which SCXI channels are scanned. Refer to Appendix B,
Using SCXI Channel Strings with Traditional NI-DAQ (Legacy) 7.0 or
Later
, for more information about using SCXI channels strings in
Traditional NI-DAQ (Legacy).
LabVIEW and the Virtual Channel String
For LabVIEW and Visual Basic 6, the channel string can also contain
virtual channels. For the SCXI-1102/B/C, these virtual channels are analog
input channels you create that have custom names, that perform all error
correction and scaling without additional code. Virtual channels are
particularly useful when sensors requiring different scaling factors are used
on the same SCXI-1102/B/C channel. Using virtual channels, you can use
sensors needing special scaling in a generic analog input application
without performing hard-coded scaling. If you change the scaling or want
to connect a different sensor to the SCXI-1102/B/C, no changes are needed
in the application. All that is required is creating a different virtual channel
and using its name in the channel string.
Note
You cannot mix virtual channels with the SCXI channel strings shown in the
previous section.
