National Instruments SCXI -1125 用户手册

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Chapter 5    Using the SCXI-1125
5-16
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Traditional NI-DAQ (Legacy) in LabVIEW
LabVIEW is a graphical programming environment for test and 
measurement application development with built-in easy to use tools for 
data acquisition, analysis, and display. You can use functional graphical 
blocks called subVIs to easily create a custom application that fully utilizes 
the SCXI-1125 programmable functionality. Traditional NI-DAQ 
(Legacy) provides several standard data acquisition subVIs as well as 
subVIs specifically for use with the SCXI-1125.
For applications using Traditional NI-DAQ (Legacy) in LabVIEW, there 
are two typical methods of addressing SCXI-1125 channels—virtual 
channels (specifically virtual channels) and SCXI channel strings. 
Depending on the needs of your application, you choose one of these 
channel addressing methods to use in your LabVIEW application.
When you use virtual channels, the maximum number of channels per 
E Series DAQ device is 512 in multichassis systems. NI recommends using 
the virtual channel for ease of use. Refer to Appendix B, 
, for more 
information on how to create a virtual channel.
The SCXI channel string allows you to combine large numbers of channels 
into fewer scan list entries, to measure the signal voltage level directly for 
custom scaling, and to dynamically perform an offset null compensation in 
your application. NI recommends using SCXI channel strings for more 
advanced applications. In LabVIEW, an array of these channel strings 
configures multiple modules for scanning. When using SCXI channel 
strings, you can scan up to 3,072 channels in a multichassis system using a 
single E Series DAQ device.
Note 
You cannot mix virtual channels with the SCXI channel strings within the same 
channel string array.
To use virtual channels, enter the name of a virtual channel into the analog 
input channel string. If using multiple virtual channels, enter them in a 
different index in the channel string array, or separate them using a comma.
Since you can randomly scan analog input virtual channels, you can enter 
the virtual channels you want to scan in any order or repeatedly in a channel 
string array.