Table 5. NI 9775 Channel Properties Configuration for AC Accuracy Verification
AI.ADCTimingMode
AI.Lowpass.Enable
High Speed
False
d)
Start the task.
e)
Read the samples from the NI 9775.
f)
Extract the amplitude of the 50 kHz signal from each channel. This can be done
using the "Extract Single Tone Information.vi". The output of the "Extract Single
Tone Information.vi" is in Vpk. To obtain AC amplitude error in units of dB, use the
following equation:
�� ��������� ����� �� = 20 × log
10
���
2 × 2.0�
g)
Clear the task.
6.
Compare the amplitude error to the limits in the following table
Table 6. NI 9775 Verification Limits for AC Accuracy
Test Point
1-Year Limits
Frequency
Amplitude (V RMS)
Upper Limit
Lower Limit
50 kHz
2.00
0.12 dB
-0.12 dB
Note
The test limits listed in this table are derived using the values in the
NI 9775 Accuracy Under Calibration Conditions
table.
Note
The uncertainty of the calibration standard is not included in these
limits.
7.
Set the calibrator to Standby mode (STBY).
8.
Disconnect the NI 9775 from the calibrator.
DC Accuracy Verification
Complete the following procedure to determine the As-Found status of DC Accuracy of the
NI 9775.
1.
Set the calibrator to Standby mode (STBY).
2.
Connect the NI 9775 to the calibrator as shown in the
AC Accuracy Verification
section.
3.
Set the calibrator voltage to a Test Point value indicated in the
NI 9775 Verification Limits
for DC Accuracy
table.
4.
Set the calibrator to Operate mode (OPR).
5.
Acquire and average samples.
a)
Create and configure an AI voltage task on the NI 9775 according to the following
table.
4
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NI 9775 Calibration Procedure
