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DAC AWG Question

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DAC AWG Question

Postby hawkins324 » Thu Mar 26, 2009 11:31 am

Hi

I am interested in the Picoscope 2203. I need to convert digitally stored values in a computer to analog output voltage levels, to control a device in a periodic manner. Is this possible first of all using this device, and if it is I have the following questions:

1) What is the update rate, i.e. the time between outputting one voltage level and then another voltage level in command/response routine?

2) What is the slew rate associated with this device?

3)When it says "arbitrary waveform buffer: 4096 samples" in the datasheet does this mean 4096 samples (or digital values) can be stored and thn streamed out of the device at a faster rate than the normal command/response routine? If so what is this rate?

4) In the datasheet it says "Amplitude: +/- 125mV to +/- 2V, with +/- 1V offset." Does this mean that for a single rail output it ranges from +125mV to +2V, and this is the maximum possible voltage range?

Thanks in advance to anyone who answers these questions. It would be really helpful.

Sam


Some datasheet info regarding the signal generator output section:
arbitrary waveform buffer: 4096 samples
DAC clock frequency: 2MHz
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Postby Robin » Thu Mar 26, 2009 1:04 pm

Hi

The 2203 has an arbitrary waveform generator. You can specify the waveform as a CSV file, you can draw the waveform using the waveform editor or you can use and edit a previously captured waveform.

The output voltage can change up to once every 50 ns.

Your arbitrary waveform can consist of up to 4096 samples. These will be repeated indefinitely. The maximum rate that these samples can be streamed is once every 50 ns.

When you specify your waveform, you do so using values from -1 to +1. This range can be mapped from voltages ranging from +/- 125mV to +/- 2V. You can also apply an offset of up to +/- 1V

It might help you to download PicoScope 6 and have a play. www.picotech.com/software

Have a look at the 2000 series User's Guide and the PicoScope 6 User's Guide http://www.picotech.com/document

Hope this helps

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Postby hawkins324 » Fri Mar 27, 2009 4:50 pm

Thank you for your reply, it was very helpful. One last question, although it is really not so relevant to the picoscope.

I need to perform the FFT on a signal so I originally intended to use the I&Q signalling technique to extract phase and magnitude values from the signal, and then use programming code to do the FFT.

But since the picoscope already has a spectrum analyzer ready made, is it safe to assume that the phase information is automatically extracted from the input signal to implement the FFT? and therefore I do not need to do an I&Q signalling design externally? Is this correct?
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Postby Robin » Mon Mar 30, 2009 8:16 am

Hi

The software finds the FFT of a waveform in order to display its spectrum. Only magnitude values are displayed.

I'm not familiar with the 'I&Q signalling technique', so can't help with that I'm afraid.

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Postby hawkins324 » Tue Mar 31, 2009 10:06 am

Hi,

Are the inputs of channel A and channel B sampled at the same time intervals? and

Is it possible to use the sampled array of values from channel A and B to compute my own complex FFT using the picoscope software? or would this need to be done in C (or preferably MATLAB if this is possible)?
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Postby Robin » Tue Mar 31, 2009 12:43 pm

Channels A and B are sampled with the same interval, but not at the same time.

You can save your waveform as a Matlab data file.

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Postby hawkins324 » Wed Apr 01, 2009 3:12 pm

oh, so the data can be saved in a MATLAB file, but presumably not in real time. Can the time sampled values be read in and processed in real time using C instead?

Sam
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Postby Robin » Thu Apr 02, 2009 9:28 am

Hi

Yes, you can write your own C program and we have examples that you can use.

See the 2000 series programmer's guide: http://www.picotech.com/document/pdf/ps2000pg-en.pdf

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