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National Instruments Corporation
7
SCXI-1520 Calibration Procedure
•
chans
—{0}
•
gains
—1
•
buffer
—[5000]
•
count
—5000
•
sampleRate
—10000
•
scanRate
—5000
17. Call
SCXI_Scale
to scale the data returned by
SCAN_Op
. Set the
following parameters:
•
SCXIChassisID
—The value assigned by MAX
•
moduleSlot
—1
•
channel
—The channel number from step 7
•
SCXIgain
—The gain value from step 14
•
TBgain
—1
•
DAQboard
—The device number of the DAQ device
•
DAQchannel
—0
•
DAQgain
—1
•
numPoints
—5000
•
binArray
—The array returned by
SCAN_Op
in step 16
The result is a set of scaled voltages called
scaledArray
.
18. Average the results returned by
SCXI_Scale
. Compare the averaged
result to the upper and lower limits in Table 2. If the result falls within
these limits, your module has passed this portion of the test. If the
result is outside these limits, adjust the module using the steps in the
Adjusting for Gain, Offset, and Excitation Errors
section.
19. Repeat steps 14 through 18 for the remaining gains.
20. Repeat steps 7 through 19 for the remaining channels.
Note
If all channels fall within the upper and lower limits, the gain and offset do not need
adjustment.
Verifying Voltage Excitation
This section describes how to verify the voltage excitation of the
SCXI-1520 and how to calculate new voltage excitation constants.
The calibration constants for the voltage excitation on the SCXI-1520
are calculated with respect to the onboard 2.5 V reference voltage. These
calibration constants are stored on the module EEPROM and can be read
by application software and used for software correction. You cannot
physically adjust the excitation on the SCXI-1520. If the measured values
of the excitation fall outside the limits given in Table 3, the module is not