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Issues with the AWG - Unstable wave

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Issues with the AWG - Unstable wave

Postby emmanuel » Sun Apr 24, 2016 8:11 pm

Hi,

I received my picoscope 2208 last week, and for now, I'm playing with the awg. I get strange results, especially with square waves (similar issues are present with others wave types):

When I set a frequency that is a divisor of 10 Mhz, i.e for exemple, 100 kHz, 125, 200, 250, 400, 500, 625, 1 Mhz, everything is fine. Why 10 Mhz ? Because I suspect there is a internal clock (or something like this) running at that frequency.

But with all others frequencies, the wave becomes unstable. As a consequent, the frequency is not stable too. Here is what is got in persistent mode with a 450 kHz square wave:
ImgFreq_450kHz.png
Unstable square waves. Frequency = 450 kHz (not a divisor of 10 Mhz)


There is sometimes, roughy 1/6 of the times, a delay of about 50 ns on the positive or negative part of the wave.
If I use the frequencies mentioned above, this delay disappears:
ImgFreq_400kHz.png
Perfect square waves. Frequency = 400 kHz


Is there something I'm doing wrong ?
Thanks,

Emmanuel.
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Re: Issues with the AWG - Unstable wave

Postby Hitesh » Fri Apr 29, 2016 9:37 am

Hi Emmanuel,

The effect that you are seeing is expected. The update rate of the signal generator is 20 MS/s, meaning a DAC period of 50 ns.

When you have a frequency that is not a divisor of this sample rate, there will be some jitter (50 ns as you are seeing with the 450 kHz waveform).

I hope this helps,
Hitesh

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Pico Technology
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