National Instruments SCXI -1125 ユーザーズマニュアル
Chapter 5 Using the SCXI-1125
© National Instruments Corporation
5-23
Perform Offset Null Compensation Using Traditional NI-DAQ (Legacy)
C API
C API
After configuring the system settings and module properties, you
can perform an offset null compensation programmatically using
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
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
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.
Programs»National Instruments»NI-DAQ.
Perform Acquisition Using Traditional NI-DAQ (Legacy) C API
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
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
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
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
Channel
Setting
NI-DAQ Function to Use
Significant
Parameters
Possible Parameters
Values
Gain
SCXI_Set_Gain
f64 gain
(gain setting)
1, 2, 5, 10, 20, 50, 100,
200, 250, 500, 1000,
2000
200, 250, 500, 1000,
2000
Bandwidth
SCXI_Configure_Filter
f64 freq
(filter cutoff
frequency if
filterMode = 1)
frequency if
filterMode = 1)
4.0, 10,000.0 Hz