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NI PXI-5404 Calibration Procedure
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© National Instruments
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19
Complete the following steps to calibrate the VCXO for frequency accuracy:
1.
Call
niHSSources_GenerateWaveform
(niHSSources Cal GenerateWaveform VI) to
generate a sine wave at the desired frequency 1 MHz. Set the following parameters:
•
sessionHandle
—The handle of the calibration session for the module
•
waveType
—
niHSSources_SINE
•
amplitudeInVolts
—
2
•
frequencyInHz
—
1000000
2.
Call
niHSSources_SetArbOutput
(niHSSources Cal SetArbOutput VI) to enable the
output. Set the following parameters:
•
sessionHandle
—The handle of the calibration session for the module
•
outputState
—
niHSSources_ENABLE
3.
Call
niHSSources_InitializeVCXOCalibration
(niHSSources Cal
InitializeVCXOCalibration VI) to reset the internal variables held by the session to begin a
VCXO calibration. Set the following parameters:
•
sessionHandle
—The handle of the calibration session for the module
•
type
—
niHSSources_SET_VCXO
4.
Repeat steps 4a–4c 16 times to adjust the frequency accuracy:
a.
Call
niHSSources_CalibrateVCXO
(niHSSources Cal CalibrateVCXO VI) to
program the adjusted VCXO DAC value to the hardware. Set the following
parameters:
•
sessionHandle
—The handle of the calibration session for the module
•
type
—
niHSSources_SET_VCXO
b.
Measure the frequency at the SINE out or CLOCK out on the NI 5404.
c.
Call
niHSSources_CalAdjust
(niHSSources Cal CalAdjust VI) to adjust the
internal VCXO DAC value. Set the following parameters:
•
sessionHandle
—The handle of the calibration session for the module
•
measurementMode
—
niHSSources_SET_VCXO
•
actualData
—A pointer to a variable that holds the desired frequency
(
1000000 Hz
). In LabVIEW, insert all inputs into an array of one element
before passing it to the VI.
•
measuredData
—A pointer to a variable that holds the measured frequency
(in Hz). In LabVIEW, insert all inputs into an array of one element before passing
it to the VI.
Tip
If the difference between the desired and measured frequencies is smaller than
the accuracy or resolution of the measurement device, you can stop the calibration at
any time.