Acquring an anolog signal outputed from a photo detector by DAQ6052E

[kaiqujian]

Hello there,

Currently, I have a NI 6052 E card and I want to use it to acquire the output anolog signal from a photo detector (PDA36A, thorlab).

Through the oscilloscope, the absolute value (peak to peak value) of the output anolog signal (voltage) is around 50mv. Then, I use the Cont Acq&Graph Voltage-Int Clk.vi to acquire the signal through the anolog input 0 of the 6052 card. The minimum and the maximum voltage are set as -50mv, 50mv respectively. Then, I excecute the vi and use an indicator to demonstrate the acquired the data. The data is constant: 0.049998. Then I highlightly excecute the program, the Error 200279 (Measurements: Attempted to read samples that are no longer available. The requested sample was previously available, but has since been overwritten.) happens.

So i do not know why the anolog signal (voltage) cannot be acquired correctly by use of the 6052E card.

Thanks,

Qiang

[Dennis_Knutson]

I'm confused. You say the amplitude with the scope and DAQ card is both 50mv. What is the problem? Ignore the error. That is just because you are using highlight execution which slows down the VI so much that you can't transfer data fast enough from the DAQ board.

[kaiqujian]

Hi, Dennis,

thanks for your reply.

I am sorry i did not clearly describe my problem. Actually, I want to acquire a sine signal whose maximum amplitude is about 50mv. The sine signal is shown in the scope.

However, when I use the programm to acquire the sine signal through the ai0 of 6052E, I get a DC signal rather than a sine signal.

So I try to acquire another sine signal whose maximum amplitude is 5v and I can get a sine signal through the aio. I attach two waveform graph. Graph 1 is the 5v sine signal shown in scope. Graph 2 is the signal acquired through the ai0. As shown in graph 2, it is a sine signal but it is not exactly the same as the input analog signal shown in graph 1. Can you tell me why?

Besides, if I decrease the sine signal into 1 v, I cannot get a sine signal anymore through the ai0. The required signal become a DC signal. So the card cannot acquire signal lower than 1 v?

Thanks,

kaiqujian

[Dennis_Knutson]

Of course you can acquire a signal less than a volt.

All that you have provided is a couple of images that really don't explain what you are doing. You are using the default configuration. Determine whether the default configuration is differential or RSE. Is the default what you want? Is the default configuration the way you have the input wired? How exactly did you wire the inputs to the DAQ board. Did you review the wiring recomendations in the manual? If your input signal is 50mv, why do you have the limits set to +/- 10 volts? 

[MattBradley]

Sounds to me like a wiring problem.  If it was me, it would have been because I switched my signal and ground lines.

[kaiqujian]

Hi, Matt,

thanks. It is a wiring problem which has been solved.

kaiqujian