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NI PXI-5404 Calibration Procedure
5.
Measure the duty cycle of the CLOCK output using an oscilloscope specified in Table 1.
To determine if the measured duty cycle is within the specification of the NI 5404, you must
determine the measurement error of the oscilloscope that you used to measure the duty
cycle and account for this error when comparing the measured duty cycle to the duty cycle
accuracy listed in the
Specifications for the NI PXI-5404
.
6.
Call
niFgen_ConfigureStandardWaveform()
to select the channel to output a
waveform. Set the following parameters:
•
vi
—The output value
sessionHandle
you obtained from the
niFgen_init
function
•
Channel_Name
—
"0"
•
Amplitude
—
5
•
Frequency
—
25000000
•
Waveform
—
NIFGEN_VAL_WFM_SQUARE
•
Start phase
—
0
•
DC offset
—
0
7.
Measure the duty cycle of the CLOCK output using an oscilloscope specified in Table 1.
To determine if the measured duty cycle is within the specification of the NI 5404, you must
determine the measurement error of the oscilloscope that you used to measure the duty
cycle and account for this error when comparing the measured duty cycle to the duty cycle
accuracy listed in the
Specifications for the NI PXI-5404
.
8.
Call
niFgen_close()
to close the instrument I/O session, destroy the instrument driver
session and all of its properties, and release any memory resources the driver uses. Set the
following parameter:
•
vi
—The output value
sessionHandle
you obtained from the
niFgen_init
function
External Adjustment
This section describes the basic external adjustment steps for the NI 5404.
Overview of Calibration Constants
External calibration determines the value of several calibration constants, which are stored in
nonvolatile memory on the module. NI-FGEN uses these constants to determine values to write
to the hardware to compensate the output. Three different sets of calibration constants are
determined during external calibration: constants for the voltage controlled crystal oscillator
(VCXO) digital-to-analog converter (DAC), the GAIN DAC, and the SYNC DAC.
VCXO DAC
The VCXO DAC tunes the onboard VCXO. Calibrating the VCXO DAC, therefore, calibrates
the frequency accuracy of the output.