NI 9205 data acquisition through CRIO

[kiani]

I am using CRIO 9022 as DAQ system. In which I m using NI 9205 ADC module to capture analog data. 

I have tried to acquire simple sinusoidal signal both in scan and FPGA mode.

For scan mode I have followed the given example in Labview for 9205. Shape of the signal is fine but not the amplitude and frequency.

Same is the problem in FPGA mode. But here I get accurate frequency but amplitude is the multiple of thousand and not making any sense. I have already tried to change the data type of FIFO from I16 to FXP but no useful outcome.

Any help in such Regard will highly be appreciated!!

[Doug-B]

Hey kiani,

Is there any chance you can send in some screenshots of the data you are getting in LabVIEW. I am interested to see what the input you are getting looks like. Also sending in some screenshots of you code that would also be helpful.

Thanks,

Doug B

[GregFreeman]

What's your sample rate and what is the wave's frequency?

[kiani]

Dear Doug,

Attachment contains my code file. In which CRIO_target is running on FPGA and CRIO_host is running on CRIO. 

My Setup is simple that , that I have connected function generator at channel 1 and I am using single ended configuration for which I have ground at appropriate place which is common ground.

From the code I am getting exact frequency for the sinsuoidal signal uptill 102KHz.Although NI 9205 can support around 225 KHz. But I am not getting accurate anything above 102K.

Regarding amplitude it's giving me a multiple of around 3000, right from the very start when I acquire signal in FPGA. Moreover, the data type shown  for acquisition channel is word which is normally FXP but i don't know when I drag the channel in my VI it apperars as word.

For FIFO I have tried number of data type, but problem is before that during acquisition, but please if you could tell me which data type for FIFO is more suitable.

Moreover, If you can please suggest my any online material to get started with CRIO FPGA and 9205 in particular.

Kind Regards,

Sohaib Kiani

[kiani]

sample rate as I configured my ADC module to 222 Khz that the maximum 9205 can support. and I am giving an input signal from 1Hz to 150 Khz. But it's only giving my accurate frequency uptil 102 K and amplitude is multiple of 3000.

[Doug-B]

Hey kiani,

Is there any way you could send in screenshots of the actual waveforms you are seeing in LabVIEW? That would make it a lot easier to follow what exactly you are describing. As for the signal starting to get messed up when you start sampling at around 102KHz, that might have to do with aliasing, as you need to sample you data at twice the frequency of the waveform to get an accurate reading.

http://zone.ni.com/reference/en-XX/help/370592N-01/digitizers/nyquist_theorem/

Thanks,

Doug B