National Instruments SCXI -1125 用户手册

© National Instruments Corporation

After configuring the system settings and module properties, you 
can perform an offset null compensation programmatically using 

SCXI_Calibrate

. 

SCXI_Calibrate

 takes measurements and adjusts the 

coarse and fine offset null potentiometers to minimize or eliminate any 
electrical offset for a channel. Repeat this process for each channel by 
calling the 

SCXI_Calibrate

 function in a loop. Use the resulting 

imbalance in your application as a software correction factor by 
determining the residual voltage from the imbalance, and subtracting this 
residual offset from each future measurement. For more information 
regarding the operation of 

SCXI_Calibrate

, refer to the Traditional 

NI-DAQ (Legacy) Function Reference Help installed by default in Start» 
Programs»National Instruments»NI-DAQ.

There are several NI-DAQ functions you can use to take measurements. 
Usually in SCXI the preference is to take multiple samples from multiple 
channels using the 

SCAN_Op

 function. 

SCAN_Op

 performs a synchronous, 

multiple-channel scanned data acquisition operation. 

SCAN_Op

 does not 

return until Traditional NI-DAQ (Legacy) acquires all the data or an 
acquisition error occurs (MIO, AI, and DSA devices only). For this reason, 
it is sometimes useful to use 

SCAN_Op

 in conjunction with the function 

Timeout_Config

, which establishes a timeout limit synchronous 

functions to ensure that these functions eventually return control to your 
application. After acquiring data using 

SCAN_Op

, the resultant data is not 

organized by channel, so you should demultiplex the data using 

SCAN_Demux

. 

SCAN_Demux

 rearranges, or demultiplexes, data acquired by 

a 

SCAN_Op

 into row-major order, meaning each row of the array holding 

Table 5-8.  NI-DAQ Functions Used to Configure SCXI-1125 

Gain

SCXI_Set_Gain

f64 gain

 

(gain setting)

1, 2, 5, 10, 20, 50, 100, 
200, 250, 500, 1000, 
2000

Bandwidth

SCXI_Configure_Filter

f64 freq

 

(filter cutoff 
frequency if 
filterMode = 1)

4.0, 10,000.0 Hz