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From: Don Y <blockedofcourse@foo.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Low spec 'scope.
Date: Wed, 28 Aug 2024 13:05:44 -0700
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On 8/28/2024 9:05 AM, Martin Brown wrote:
> On 28/08/2024 16:32, Don Y wrote:
>> On 8/28/2024 7:47 AM, Martin Brown wrote:
>>> On 28/08/2024 08:39, Liz Tuddenham wrote:
>>>> The recent thread on high-end oscilloscopes has reminded me of a project
>>>> that I shelved some years ago and might be due for resurrection:  I am
>>>> looking for a real-time display about 3" x 4" that can behave as an X-Y
>>>> oscilloscope with a bandwidth of about 100 Kc/s; a flat panel would be
>>>> ideal.
>>>>
>>>> Currently I am using an actual X-Y oscillocsope to monitor the output
>>>> from a stereo gramophone cartridge, which allows me to check historic
>>>> discs for damage or faulty recording geometry.  The tube is about 14"
>>>> long, which means it has to be a standalone shelf unit and I can't build
>>>> anything like it into portable equipment.
>>>
>>> I think that Daqarta software can probably do about what you want using the 
>>> PC stereo soundcard to digitise X & Y. 100kHz bandwidth might be pushing it 
>>> but it should be fine for audio up to 20kHz.
>>
>> Does it *simultaneously* sample each channel?  Or, toggle between them?
> 
> I have never looked hard enough or at a high enough frequency to tell the 
> difference.

The OP would have to consider whether or not that would be significant
to their needs.  I.e., a *real* 'scope would be driving the X&Y deflection
amplifiers simultaneously.  No idea how the anomalies sought would
manifest...

> Audio demo's work best around 440Hz orchestral A which most people 
> can hear well. Waveform shapes and sounds are fun demos.
> 
> The guy knows what he is doing so I expect it is simultaneous sampling of the 
> waveforms to within a few memory cycles. Skew only becoming a problem at very 
> high frequencies. It is cute there is a free trial period and you get to keep 
> the (audio) waveform generator.

But, wouldn't that depend on the *hardware's* capabilities?
I've not looked at the details of a sound card since the PAS-16 (!)
so have no idea what the current "standards" dictate.  Now, I only
use sound cards to play music...

> There is something similar for Android tablet/phones too but I don't think that 
> one does X-Y Lissajous figures (I could be wrong about that). The waterfall 
> spectrograph is quite a handy toy to have on your phone...
> 
>> The advantage would be that you could locate the data acquisition
>> hardware separately from the (COTS) display.
> 
> It is a neat piece of software. Every now and then AV codes take against it 
> because it does do a bit of rather low level IO access (obviously).