How to use USB-6501 to generate a stable pulse wave?

[fang@7826215]

My teacher only gave me a USB-6501, but he asked me to measure a positive square wave and nine negative square waves. I think as long as a stable pulse wave with a duty cycle equal to 10% is generated.What can I do? Measure or make wave? And how?

[carmen9]

Hi,

Hope this tutorial helps:

Pulse Width Modulation (PWM) Using NI-DAQmx and LabVIEW

[fang@7826215]

Hi

The attachment is my labview program. But the program has a 200077 error. Can you help me? 

[carmen9]

Hi,

This error might be because the USB 6501 is not capable of Counter Output and can only be used for measuring (Counter Input).

The USB 6501 is software-timed, so the pulse generated will not be as accurate as a hardware-timed device.

This post might help you: 

https://forums.ni.com/t5/Digital-I-O/USB-6501-pulse-train/td-p/253690?profile.language=en

https://forums.ni.com/t5/Digital-I-O/NI-USB-6501/m-p/3239247#M20624

[Brzhou]

Hi Carmen, 

For this topic:

6501 only support  24 channels DIO and a counter.

If we want to use it to generate the pulse, then we need to set the bit to 1 and 0 toggling with dedicated delay, to meet the requirement of the duty cycle.

Since this is software timing, and not so accurate, then could be used in the simply scenario, or  low frequency.

Please correct me, thanks.

[Brzhou]

Hi Sir,

Since it is software timing, so the accuracy depends on the accuracy of your system(IPC) clock, right ? 

Thanks.

Bruce

[guserwin91]

You can refer to the example code here as reference if you are using USB-6501. 

https://forums.ni.com/t5/Example-Code/Software-Timed-Pulse-Width-Modulation/ta-p/3507768

[santo_13]

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@Brzhou wrote:

Hi Sir,

Since it is software timing, so the accuracy depends on the accuracy of your system(IPC) clock, right ? 

Thanks.

Bruce

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The accuracy of your computer's clock and the timing precision provided by the Operating System. Typically, it is in the order of ms. Another important thing is hope that your OS doesn't block the execution of the software because it has some other priority software executing, such as Windows Update; in this case, your generation will be stuck and will not update.

[Brzhou]

Hi Sir,

Thanks for your information, as long as i get a chance, will give a try.