NI myDAQ

[Cam158]

Hi everyone,

It's been a while since my last visit here and I was hoping someone my be able to help....! I have purchased the National Instruments myDAQ which came with a student copy of LabView. It has some nice pre made VI's including a function gen, however I need to produce a 350Khz pulse for a variable capacitor filter in a basic circuit and I need to know if the DAQ is limited to a certain frequency range. I have tried to create my own VI but I keep getting an error. Anyone have any hints for an amature?

Cheers

Cam

[alm]

According to the specs, the sample rate of the analog outputs is 200 kS/s, so assuming the output bandwidth starts at DC, anything above 100 kHz would be impossible based on the Nyquist-Shannon sampling theorem. According to the manual, the function generator has an output frequency range from 0.2 Hz to 20 kHz, probably because of the output filter and multiple waveforms. Not sure how nice the pulse would be at 20 kHz, it may be slightly rounded due to the finite frequency response of the output filter.

[Bored@Work]

alm mentioned the key word

According to the manual

Why didn't you read the manual? Is that really asked too much from a student?

[slateraptor]

Not sure how nice the pulse would be at 20 kHz, it may be slightly rounded due to the finite frequency response of the output filter.

It's shit. Unfortunately, MyDAQ is effectively useless beyond audio bandwidth.


EDIT:

According to the specs, the sample rate of the analog outputs is 200 kS/s, so assuming the output bandwidth starts at DC, anything above 100 kHz would be impossible based on the Nyquist-Shannon sampling theorem.

It's worse than that; if memory serves correctly, I don't think the software even implements sinc interpolation.

[caffeinatedbard]

As an alternate suggestion to the apparent limitation of myDAQ, you could try and make a PLL circuit that is controlled by your myDAQ.

Another suggestion would be to use a microcontroller and build a simple RS-232 VI in labview to tell the frequency you desire.  You would probably need some extra circuitry to make sure the signal is stable and jitter free but it seems like a fun project anyways.

Good luck!