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National Instruments Corporation
23
NI 5122/5124 Calibration Procedure
•
coupling
:
NISCOPE_VAL_DC
•
probeAttenuation
:
1.0
•
enabled
:
NISCOPE_VAL_TRUE
3.
Call
niScope_ConfigureHorizontalTiming
(niScope Configure
Horizontal Timing VI) with the following parameters:
•
minSampleRate
:
100,000,000
•
minNumPts
:
1,000,000
•
refPosition
:
50.0
•
numRecords
:
1
•
enforceRealtime
:
NISCOPE_VAL_TRUE
4.
Call
niScope_Commit
(niScope Commit VI) with the following
parameter:
•
vi
: The instrument handle you obtained from
niScope_init
5.
Connect the calibrator test head directly to the channel 0 input of the
digitizer. Configure the calibrator to output an exact 11 MHz sine wave
with 1 V peak-to-peak amplitude and 50
Ω
load impedance.
6.
Wait 750 ms for the impedance matching and frequency of the
calibrator to settle.
7.
Call
niScope_InitiateAcquisition
(niScope Initiate
Acquisition VI) with the following parameter:
•
vi
: The instrument handle you obtained from
niScope_init
8.
Call
niScope_FetchMeasurement
(niScope Fetch
Measurement VI) with the following parameters:
•
channelList
:
"0"
•
timeout
:
1.0
•
scalarMeasFunction
:
NISCOPE_VAL_FFT_FREQUENCY
9.
Compute the error in timing as parts per million (ppm) using the
formula:
error = (
a
– 11,000,000) / 11
where
a
is the measured frequency.
Compare the result to the Calibration Test Limits or the Published
Specifications listed in Table 9. If the result is within the selected test
limit, the device has passed this portion of the verification.
Table 9.
NI 5122/5124 Timing Accuracy
Calibration Test Limits
Published Specifications
±5.3 ppm
±25 ppm