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Timebase scaling - ADC-100

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Timebase scaling - ADC-100

Postby Richard Rudd » Tue Mar 18, 2003 10:25 am

I'm trying to get to grips with a new ADC-100, which I'm using with a Dell 1.6 GHz machine/Win 2000. I needed the parallel converter and had to set up the patch.

My problem is that, in scope mode, the timebase scaling seems to be wrong by a factor of 3 (a 1kHz sinewave occupies 3ms/cycle rather than 1ms. When I use the spectrum analyser, the frequency is displayed correctly when I set the maximum frequency to less than 10 kHz. At 10kHz, the trace extends only to ~2.5 kHz and the measured frequency appears to be around 330 Hz.

Is this a sample speed/aliasing problem, or have I simply failed to set up the software correctly? The 'help|about' dialog shows that the device is only achieving 37,622 samples/second (which is a problem as I bought the device to capture a signal running at 20-30 kHz!)

Richard Rudd

Postby matthew » Wed Mar 19, 2003 1:33 pm

Hi Richard,

The ADC-100 speed can be increased from Settings|Options|Advanced. Increase the number of samples per scope trace. Some PCs can be slower than others, this is usually due to the operating system (Win98 is often quicker) but not usually by very much in PicoScope.

With regards to the frequency problem, do you have a USB adapter or are you using the parallel port directly. You can email the psd file to me to tech@picotech.com, showing both the spectrum peak at 1kHz and the scope trace at around 1ms/div (in the same file / captured at the same time) - I will look into this for you.

Best Regards,
Matt Everett

Pico Software Engineer
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