AC test of PCI NI 6289

[giuan]

Hi,

I am performing AC test on the NI 6289; i want to do the FFT testand sine3fit test.

I use the AC calibrator DATRON Wavetek 4707 as function generator; I acquire a waveform signal nearly at full scale with a frequency evaluated to the formula fs=j/M*fc (fs: signal frequency, M number of points, fc:sampling rate; J and M relatively prime) to acquire an nteger number of period. Neverthless i am not able to measure more than 70 dB (~12 bit). I always note a spectral leackage effect around the main harmonic.

Is it a problem of jitter? or do you think i do some errors in my tests?

Do you have further suggestion?

Thanks a lot for you help

Giovanni

[shommes]

Hi,

could you give me further information about your measuring?

Do you aquire data with labview and then communicatin with teststand?

[giuan]

Hi,

I acquire the data on the PC, through Labview; then i perform the tests in labview or in Matlab; the test follows the satndard IEEE 1057 1994.

After a further investigation, i see that the non linearity (2nd, 3rd, 5th and 7th harmonics) and a small effect of  spectralleackage decreases the performance; at this precision i neoted that a point on the period cycle of the sine wave makes difference.

Any usefuyl suggestioon is welcome

Thanks a lot,

Jiuan

[shommes]

Hi,

What do you mean by an inability to get more than 12-bits of resolution? How are you verifying that? Can you try using any normal routines in LabVIEW and get the same information?

Are you sure that your hardware isn't defective?

[giuan]

Hi,

I do a very simple analysis

I acquire the signal and I do the FFT;

then i evaluate the Noise Power and signal power. by the SNR I calcualt the ENOB

SNRdb = 6.02*ENOB+1.76

do you know special function in Labview for doing this?

Anyway,  As i see sporious harmonics, i was wondering about the goodness of the PGA that is mounted on the board.

did you do a similar test? On the NI datasheet, the THD and the SNR is not specified.

Otherwise i have to think thet the calibrator is not adpt, but form the datasheet, it seems pretty good

Thaks a lot,

Jiuan

[shommes]

Hi,

my Customer wrote me this recently:

-----------------------------------------
I do a very simple analysis
I acquire the signal and I do the FFT;
then i evaluate the Noise Power and signal power. by the SNR I calcualt the ENOB
SNRdb = 6.02*ENOB+1.76

do you know special function in Labview for doing this?

Anyway, As i see sporious harmonics, i was wondering about the goodness of the PGA that is mounted on the board.

did you do a similar test? On the NI datasheet, the THD and the SNR is not specified.

Otherwise i have to think thet the calibrator is not adpt, but form the datasheet, it seems pretty good
----------------------------------

Any ideas?

Thanks