NI 449
x
Calibration Procedure | © National Instruments | 11
4.
If verifying an NI 4492/4497/4499 and the coupling changes from DC to AC, commit the
configuration using the DAQmx Control Task VI and wait 5 seconds for the input to settle.
5.
Start the task.
6.
Acquire readings with the NI 449x.
7.
Stop and clear the task.
8.
Calculate the rms amplitude of the acquired fundamental harmonic. You will use the
measured amplitude as V
1 kHz
in Table 14.
9.
Repeat steps 2 through 8 for each row in Table 14. In step 2, instead of generating a 1 kHz
tone, configure the calibrator to generate the frequency listed in Table 14. The calibrator
output amplitude will remain constant. When generating the 20 Hz tone, acquire
131,072 samples per channel in step 3, as opposed to the usual 102,400.
Take the amplitude calculated in this step and compare it to the appropriate limits in
Table 14. The value of V
1 kHz
is the measured amplitude of the 1 kHz tone.
10. Repeat steps 2 through 9 for each gain setting that your device supports. Refer to Table 12
for the gain settings supported by NI 449x devices. In step 2, change the output of the
calibrator based on the gain setting that is being verified. Set the amplitude to the value
listed in Table 7 for the NI 4495/4496/4498 or Table 8 for the NI 4492/4497/4499 for the
specific gain setting. When performing step 3, adjust the gain parameter appropriately.
Samples per channel
102,400
When sampling the 20 Hz tone, acquire
131,072 samples per channel.
Gain
0 (dB)
Physical channel
Dev_name/ai0
*
Coupling
If verifying an NI 4495, DC. Otherwise, AC.
*
Dev_name is the name shown for the NI 449x in MAX.
Table 12.
Supported Gain Settings
Device
Gain Settings
NI 4492
0 dB, 20 dB
NI 4495
NI 4496
NI 4497
NI 4498
0 dB, 10 dB, 20 dB, 30 dB
NI 4499
Table 11.
NI 449x AI Flatness Verification Configuration (Continued)
Configuration
Value
