Chapter 3
Adjustment
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National Instruments Corporation
3-5
e.
Call
ni54xx_SetOutputImpedance
to set the output impedance
to 50 ohms using the following parameters:
•
sessionHandle
—The handle of the calibration session for the
device
•
impedance
—
NI54XX_50_OHMS
f.
Call
ni54xx_SetArbOutput
to enable the device output using
the following parameters:
•
sessionHandle
—The handle of the calibration session for the
device
•
outputState
—
NI54XX_ENABLE
3.
Go to the appropriate section below to guide you through calibrating the
desired constant.
4.
Repeat steps two and three for each set of constants you wish to calibrate.
5.
Call
ni54xx_CalEnd
to close the session using the following
parameters:
•
sessionHandle
—A pointer to the handle of the calibration session
for the device
•
action
—
NI54XX_ABORT
or
NI54XX_COMMIT_CONSTANTS
You may either commit the constants you have calculated or abort the
whole session. Aborting saves no changes to the device.
Finding the Low Frequency Characteristics
of the Analog Channel
To find the low-frequency characteristics of the analog channel, calibrate for
the constants A0–A8, A9 (terminated) and A9 (unterminated). You should
calculate constants A0 through A8 in the order the sections appear below.
Take all measurements for A0 through A8 unterminated (across a
high-impedance load). To find the low frequency characteristics of the analog
channel, complete the numbered steps in each section below in the order the
sections appear for constants A0 to A9.
Determining Output Dependence On the Gain of the
Offset Calibration DAC (Constant A1)
To determine the output dependence, measure output while sweeping the full
scale of values for the offset calibration DAC, with the gain calibration DAC
and the main DAC set to 0. To sweep the full range of the offset calibration
DAC, write nine values to the device: (–8192, –6144, –4096, –2048, 0, 2048,
4096, 6144, and 8191).