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National Instruments Corporation
49
NI 5421/5441 Calibration Procedure
12. Call
niFgen_CalAdjustDirectPathGain
(niFgen Cal Adjust
Direct Path Gain VI) using the following parameters:
•
vi
: The session handle returned from
niFgen_InitExtCal
•
channelName
:
"0"
•
mainDACValues
: An array containing two elements—the two
values (
32767
, –
32767
) that you set on the main DAC in order
•
gainDACValues
: An array containing four elements—the four
values (
1800
,
2600
,
1500
,
2300
) that you set on the gain DAC in
order
•
measuredOutputs
: An array containing four elements—the
four output voltages (
measurement 0
,
measurement 1
,
measurement 2
,
measurement 3
) that you measured in order
Adjusting the Oscillator Frequency
Adjusting the oscillator frequency involves generating a sine wave at a
desired frequency, and then iteratively measuring the frequency, passing
the measured value to NI-FGEN so that the oscillator can be adjusted, and
then re-measuring the resulting frequency. This process is repeated until
the difference between the desired and measured frequency falls within the
desired tolerance 4.5 ppm. This adjustment ensures the frequency accuracy
of the onboard oscillator.
1.
Call
niFgen_InitializeOscillatorFrequencyCalibration
(niFgen Initialize Oscillator Frequency Calibration VI) using the
following parameter:
•
vi
: The session handle returned from
niFgen_InitExtCal
2.
Call
niFgen_SetAttributeViReal64
to set the sample rate
(niFgen property node:
Arbitrary Waveform Output»Sample Rate
)
using the following parameters:
•
vi
: The session handle returned from
niFgen_InitExtCal
•
channelName
:
"0"
•
attributeID
:
NIFGEN_ATTR_ARB_SAMPLE_RATE
•
value
:
100000000
3.
Call
niFgen_SetAttributeViReal64
to set the gain (niFgen
property node:
Arbitrary Waveform Output»Arbitrary Waveform
Gain
) using the following parameters:
•
vi
: The session handle returned from
niFgen_InitExtCal
•
channelName
:
"0"
•
attributeID
:
NIFGEN_ATTR_ARB_GAIN
•
value
:
1
Note
You can adjust this value based on which measuring device you use.
