External Adjustment; Overview Of Calibration Constants; Vcxo Dac - National Instruments 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()
waveform. Set the following parameters:
• vi—The output value
function
• Channel_Name—
• Amplitude—
• Frequency—
• Waveform—
• Start phase—
• DC offset—
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()
session and all of its properties, and release any memory resources the driver uses. Set the
following parameter:
• vi—The output value
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.
14 | ni.com | NI PXI-5404 Calibration Procedure
sessionHandle
"0"
5
25000000
NIFGEN_VAL_WFM_SQUARE
0
0
to close the instrument I/O session, destroy the instrument driver
sessionHandle
to select the channel to output a
you obtained from the
you obtained from the
niFgen_init
niFgen_init