Max sample rate with NI 9205 - Problems

[ThiCop]

Hello Subir,

If  I can do anything for you in the meanwhile, then please let me know.

From now on my forum response time should be back to the normal level.

[subir · Accepted solution]

Dear ThiCop,

thanks for waiting so long. So finally the 9215 has solved the issue. I following pictures show that.

The hardware was as usual. I didnt have all the engine and test bench so i just input sine wave as the pressure signals and the same for torque signals (hence the two graphs). The timing clocks were also generated by another function generator(external) . the pressure graph (top) was aquired by NI 9215, and the torque graph (bottom), was aquired by 9205 at 8 microsecond conversion time. both were sampled at 90 K samples/second. As you can see the difference is stark, there is excessive cross talk in the 9205. This crosstalk diminishes if i dont sample more than 1 channel. i tried that and it behaved almost like 9215. Also note that the amplitude of 9205 is wrong since this is an averaged output, over 50 cycles and each time a cycle is averaged, the points dont add up correctly, ultimately increasing the error.

So conclusion, if you want good signal at high sampling rates, dont use a multiplexing card, and if you do, please common all the inputs to ground to reduce impedances and maybe you will have better signal (didnt work for me)..

I am attaching my code so that if someone wants to not repeate the mistakes i did, which is however the real learning 🙂

Thanks for the help!!

[ThiCop]

Hello subir,

It's indeed always a good idea to be very thoughtful about grounding considerations with multiplexed (and actually also with non-multiplexed) cards.

In general you will however see less "grounding problems" with simultaneous sampling, because you're not sharing the ADC.

[aarthiem]

Dear all,

it is not exactly pertained with daq but I want to know about the maximum sampling rate of my hardware. So I want to calculate frequency of the analog values obtained in the waveform graph . Can anyone please help me????

[Dennis_Knutson]

You should have created a new thread. What is your hardware? The maximum sample rate of all NI DAQ devices is listed on the product page and in the specifications.

[aarthiem]

well actually its not a daq.  its arduino uno. 

new thread as in?

[Dennis_Knutson]

As in don't hijack an old and unrelated thread. Start a new one.

Surely you have specs on the arduino and the a/d it uses.

[aarthiem]

I do know its ADC  sampling rate. my problem isnt that. After being interfaced with labview i would like to check its speed in labview.

[Dennis_Knutson]

If you knew the sample rate, why did you ask about it?

What speed are you actually wanting? The baud rate?

Please be specific. You've posted three times and I'm totally unclear on what you want.

[aarthiem]

Am sorry. 

I want to know the maximum frequency that can be obtained by an arduino while interfaced with labvieew. The thing is i am setting up an entire system using labview and monitoring it. so the sensors connected to arduino, whose values am viewing in labiew, I would like to know how many samples per second can be obtained , when interfaced with arduino. 

Because, i read that it doesnt offer much accuracy after 5khz but i would like to test it and see for myself as well. 

hence I requested as to what is the way to know the maximum frequency or sampling rate  that can be obtained.