Generating 80 kHz sine wave output with USB-6453

[JayWW]

Hello,

   I'm attempting to generate an 80 kHz sine wave using the USB-6453 analog output. I've been tinkering with an example (Voltage - Finite Output.vi) and so far what I've discovered is, with the max sampling rate at the analog output of 250kS/s, it's not high enough to get a clean sine wave at 80 kHz. From what I've seen, you need a sampling rate of approximately 25x the desired frequency to get it out clean. I've tried using regeneration, see attached VI. But is there an easy way to route a faster internal clock to get the faster sampling rate? Or do I need to bring in an external clock?

Any recommendations are appreciated!

Thanks!

[GerdW]

Hi Jay,

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@JayWW wrote:

what I've discovered is, with the max sampling rate at the analog output of 250kS/s, it's not high enough to get a clean sine wave at 80 kHz.

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Yes.

Mr. Nyquist is calling…

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@JayWW wrote:

But is there an easy way to route a faster internal clock to get the faster sampling rate? Or do I need to bring in an external clock?

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When the AO is specified to output at 250kS/s max then you don't have any way to output at higher sample rates. Point.

When you need higher sample rates then you need to buy better DAQ hardware. (Reading the specs before ordering might help, too. :D)

[Henrik_Volkers]

you can try a external low pass filter..

What THD you need?

[JayWW]

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@Henrik_Volkers wrote:

you can try a external low pass filter..

What THD you need?

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THD isn't super critical. That being said, I am trying to generate function generator caliber signals. What would implementing a low pass filter accomplish?

Thanks!

[Henrik_Volkers]

Just a small analog circuit. one or two OP and some Rs and Cs..

https://tools.analog.com/en/filterwizard/

[Henrik_Volkers]

Another hack: 

Use the digital outputs with  resistors (R2R or in log2 scale) to build a 8bit DA ....   

digital wfrm can go up to 10MSPS, but I don't know the details of your 6453....

[santo_13]

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@JayWW wrote:

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@Henrik_Volkers wrote:

you can try a external low pass filter..

What THD you need?

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THD isn't super critical. That being said, I am trying to generate function generator caliber signals. What would implementing a low pass filter accomplish?

Thanks!

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very clean sine wave has very low THD, so, yes, THD is important

[Henrik_Volkers]

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@santo_13 wrote:

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@JayWW wrote:

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@Henrik_Volkers wrote:

you can try a external low pass filter..

What THD you need?

---

THD isn't super critical. That being said, I am trying to generate function generator caliber signals. What would implementing a low pass filter accomplish?

Thanks!

---

very clean sine wave has very low THD, so, yes, THD is important

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I have to agree 100% to santo_13 ,  what do you mean with "generate function generator caliber signals"?  

calibration?  synchronisation?   

What do you want to do? 

[JayWW]

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@Henrik_Volkers wrote:

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@santo_13 wrote:

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@JayWW wrote:

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@Henrik_Volkers wrote:

you can try a external low pass filter..

What THD you need?

---

THD isn't super critical. That being said, I am trying to generate function generator caliber signals. What would implementing a low pass filter accomplish?

Thanks!

---

very clean sine wave has very low THD, so, yes, THD is important

---

I have to agree 100% to santo_13 ,  what do you mean with "generate function generator caliber signals"?  

calibration?  synchronisation?   

What do you want to do? 

---

THD isn't hyper-critical for my application. I just need a decent sinusoidal waveform, at 80 kHz, and a specific amplitude, for two seconds on, and 8 seconds off. 

[santo_13]

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@JayWW wrote:

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@Henrik_Volkers wrote:

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@santo_13 wrote:

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@JayWW wrote:

---

@Henrik_Volkers wrote:

you can try a external low pass filter..

What THD you need?

---

THD isn't super critical. That being said, I am trying to generate function generator caliber signals. What would implementing a low pass filter accomplish?

Thanks!

---

very clean sine wave has very low THD, so, yes, THD is important

---

I have to agree 100% to santo_13 ,  what do you mean with "generate function generator caliber signals"?  

calibration?  synchronisation?   

What do you want to do? 

---

THD isn't hyper-critical for my application. I just need a decent sinusoidal waveform, at 80 kHz, and a specific amplitude, for two seconds on, and 8 seconds off. 

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In that case, then a 250ksps sample rate should give you a "decent" sinewave at 80kHz as it already satisfies the Nyquist criteria.