Unable to get the frequency values using Flex RIO adaptor module

[AnveshRaJA]

Helloo!

 I started to run gettingstarted.lvproj file from the examples got with the labview package. I compiled it successfully and I ran it. The output I am seeing (I mean waveform) is very different with the given input, frequency is not matching with the input. I dont know whether the output is correct or not, as I am new in using labview.

 If I am thinking wrong then, please enlighten me regarding this concept or else tell me where I have gone wrong.

For more information, I am using NI 5734 adaptor module with NI PXIe-1073 chassis.

Thanks in advance,

Sincerely,

K A Raja 

[Roberto_DS]

Hi Anvesh, 

I'd be happy to look into this for you. Unfortunately I cannot find the exact example you are running so could you reply to this with the file attached so I can try replicate your issue?

The digitiser you mentioned (NI 5734) is a 4 channel output adaptor - is this where you have your input?

Where are you measuring the output?

Best Regards,

Roberto

NI UK AE

[AnveshRaJA]

I will summarize to you our problem. We are recording a 20 kHz sinusoidal wave (we check the frequency with an oscilloscope....).

We fix the sampling rate at 100 kS per second and the number of samples to 50 k. We expect to receive a 0.5 seconds signal consisting on about 10000 oscillations. I attach to you a screen copy of the vi program, together with the data file and the representation in Origin. 

Surprisingly we obtain a signal of 0.5 s (OK) having a few oscillations (around 8 oscillations, instead of 100000). The period of the oscillation is arround 60 msec, instead of 1/20k. 

If we change the sampling rate, maintaining the frequency, we found that the period of the signal changes accordingly (which is not normal). If we reduce the sampling rate to 1/2, the 'period' increases 2 times. This suggest that the system takes the sample number, instead of time.

The changes in the time scale are not dramatic for us (but it will be nice to understand what happens). The main problem is that it seems that the system is capturing less signal than expected. It seems that it captures only 8 oscillations instead of the 10000  that occurs in 0.5 seconds. Yes, we are using the digitiser you mentioned (NI 5734) is a 4 channel output adaptor with AI0 is the input port, from which the input is given.

Thanks for your help. We are waiting for the reply.

Sincerely,

Anvesh Raja K