National Instruments SCXI -1125 用户手册

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页码 101
Chapter 5    Using the SCXI-1125
© National Instruments Corporation
5-25
support virtual channels using Data Neighborhood (DAQ Channel Wizard) 
in MAX. In LabWindows/CVI, C, or C++ development environments, 
several NI-DAQ function calls need to be made to set up each module 
involved in the scan, the chassis, and the E Series DAQ device controlling 
the scan. In Measurement Studio, SCXI channels must be configured as 
virtual channels (tags) in MAX.
A discussion describing how to implement multiplexed scanning in the 
different ADEs follows. Refer to your 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, the channel string determines the 
sequence in which SCXI channels are scanned. In LabVIEW, an array of 
these channel strings configures multiple modules in the scan list. When the 
application program runs, the channel string is used for programming the 
channel information into the SCXI system. The format of the channel string 
is as follows:
obx ! scy ! mdz ! channels
where
obis the onboard E Series DAQ device channel, with x representing 
a particular channel where the multiplexed channels are sent. This 
value is 0 for DAQ channel 0 in a single-chassis system. In a 
multichassis or remote chassis system, however, the E Series DAQ 
device channel corresponds to chassis number n–1, where DAQ 
device channel x is used for scanning the nth chassis in the system.
scis the SCXI chassis ID, where is the number you chose when 
configuring your chassis.
mdis the slot position where the module is located, with being the 
particular slot number. The slots in a chassis are numbered from left to 
right, starting with 1.
Note 
The
 
ob
!
 
specifier is optional and causes the gains on the module and E Series 
DAQ device to be automatically set to fit the input limits parameter. When this specifier is 
omitted, the default gain on the E Series DAQ device, usually the lowest gain, is used, but 
the SCXI-1125 gain is adjusted to fit the input limits.