NI USB 6009 - Generate a continuously waveform on analog output

[rumpschelektronik]

Hi all,

i have some problems with my NI-USB 6009. I want to output a sinewave continuously on analog output port ao0.

In Labview i use the NI-DAQmx. 

My Problem is: I can generate a signal and display to analog output port, but if I measure the sinewave with an oszilloskop or show graphically in Labview, the signal isn ' t chronological constant.

What is the problem?

Can it be, that NI-USB 6009 is not compatible at this application? 

Many thanks.. Please help.

[Jan_HeG]

I am not exactly sure I understand the problem with your signal, but in the Manual (Clicky) the following info can be found:

Minimizing Glitches on the Output Signal
When you use a DAC to generate a waveform, you may observe glitches in
the output signal. These glitches are normal; when a DAQ switches from
one voltage to another, it produces glitches due to released charges. The
largest glitches occur when the most significant bit of the DAC code
changes. You can build a lowpass deglitching filter to remove some of
these glitches, depending on the frequency and nature of the output signal.
Refer to ni.com/support for more information about minimizing
glitches.

Could that be your issue?

[Coq_Rouge]

The analog out on your DAQ unit is software timed. If you are looking for a cheap solution try to use the sound card for output. This may function quite well in the audio range 20-20Khz. Let me know if you need any help in implenting it. You have all functions needed with the Labview base

[NAZ87]

Coq Rouge, How would one go about setting the DAQ with audio output.  I have the same issue as listed above.  I have the Ni USB-6008 model.

Any info would be helpful.

Thank you for your time.

~Nick

[Coq_Rouge]

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@NAZ87 wrote:

Coq Rouge, How would one go about setting the DAQ with audio output.  I have the same issue as listed above.  I have the Ni USB-6008 model.

Any info would be helpful.

Thank you for your time.

~Nick

---

I would not even try. As said before theUSB-6008 do only have software timed output. This limit the update rate to 1000 Hz. Not posible to make much audio output out of that. Why do you not use a sound card instead?

[NAZ87]

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Coq Rouge wrote:

"The USB-6008 has only software timed output. This limits the update rate to 1000 Hz."

---

I have found a sine wave will degrade much sooner; my meter can pick up the output to 500Hz.  The module manual quotes the max update rate for the AO to be 150 Hz.
 

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@COq Rouge wrote:

"Why do you not use a sound card instead?"

---

That is starting to sound like a good option.  I have found the sound pallete in the higherarchy of the Labview functions palette, but I haven't been able to sort through the specifics of creating the continuous waveform via the sound card.

Do you have an example you could supply me with?  I would appreciate it.

Thank you for your time,

~Nick

[Coq_Rouge]

---

@NAZ87 wrote:

---

Coq Rouge wrote:

"The USB-6008 has only software timed output. This limits the update rate to 1000 Hz."

---

I have found a sine wave will degrade much sooner; my meter can pick up the output to 500Hz.  The module manual quotes the max update rate for the AO to be 150 Hz.
 

---

@COq Rouge wrote:

"Why do you not use a sound card instead?"

---

That is starting to sound like a good option.  I have found the sound pallete in the higherarchy of the Labview functions palette, but I haven't been able to sort through the specifics of creating the continuous waveform via the sound card.

Do you have an example you could supply me with?  I would appreciate it.

Thank you for your time,

~Nick

---

Then thinking of it. Perhaps 150 Hz is more correct. Labview do have sound card VIs. Go to help in the toolbar then Find Examples. Search for sound. I think the VI "Generate Sound.vi" may do the job. A sound card may produce waves from about 20 to 20 KHz. But you need to calibrate the output. As the output level will vary from sound card to sound card. In a academic or experimental setting a sound card may do the job quite well. But in an commercial setting the use of a sound card may be quite awkward.

[NAZ87]

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Coq Rouge wrote:

Labview does have sound card VIs. Go to help in the toolbar then Find Examples. Search for sound. I think the VI "Generate Sound.vi" may do the job. A sound card may produce waves from about 20 to 20 KHz. But you need to calibrate the output. As the output level will vary from sound card to sound card. In a academic or experimental setting a sound card may do the job quite well. But in an commercial setting the use of a sound card may be quite awkward.

---

Thanks for pointing me in the right direction.  I have attached the Vi that I am now using to generate different signal types at the above mentioned frequency range.

You had mentioned that I need to calibrate the output.  I assume the calibration curve is simply the voltage output corrosponding to the input to the volume control.  Are there any additional steps?

Also, do you know of any way in Labview to control the way the Sound Vis change the left and right volume independantly?

Thank you for your time and help.

~Nick

P.S. Luckily I'm in an academic setting.

[Coq_Rouge]

 

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@NAZ87 wrote:

Thanks for pointing me in the right direction.  I have attached the Vi that I am now using to generate different signal types at the above mentioned frequency range.

You had mentioned that I need to calibrate the output.  I assume the calibration curve is simply the voltage output corrosponding to the input to the volume control.  Are there any additional steps?

Also, do you know of any way in Labview to control the way the Sound Vis change the left and right volume independantly?

Thank you for your time and help.

~Nick

P.S. Luckily I'm in an academic setting.

---

Here is one way to do it. Then you write a sine wave with amplitude 1 to the sound card. You will get a sine wave with the correct frequency. But not with 1 volt in amplitude. The output amplitude will depend on the settings in windows. hence you will need to do some calibration if an accurate amplitude level is needed 

[NAZ87]

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@COq Rouge wrote:

Here is one way to do it...

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I see that the Volume Control changes the waveform based on a log scale while scaling the waveform with the multiply command is a linear scale.  I assume this makes a difference when using the sound card to appropriately scale audio, but doesn't have a bearing when outputing an arbitrary waveform signal.  Am I accurate in this assumption?

According to the above, I should just set the Volume to max and scale from 1 to 0.  Is there any reason I should scale by a log scale as the Volume Control does?

Thanks for all the help.

~Nick