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From: liz@poppyrecords.invalid.invalid (Liz Tuddenham)
Newsgroups: sci.electronics.design
Subject: Re: Low spec 'scope.
Date: Thu, 29 Aug 2024 10:43:29 +0100
Organization: Poppy Records
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Jasen Betts <usenet@revmaps.no-ip.org> wrote:

> On 2024-08-28, Don Y <blockedofcourse@foo.invalid> 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.
> 
> or any other sound card scope software, 
> 
> > Does it *simultaneously* sample each channel?  Or, toggle between them?
> 
> It makes an audio recording using commodity PC sound hardware.
> https://www.ti.com/product/PCM2900C has 2 ADC channels
> 
> > The advantage would be that you could locate the data acquisition
> > hardware separately from the (COTS) display.
> 
> It's starting to feel like raspberry pi + LCD display + usb sound card.

The first bit sounds OK apart from the programming.  This is a
standalone piece of analogue equipment, so there is no computer, no USB
and no sound card (nor any possibility of them).  

If the Raspberry Pi could be made to fire itself up without any
intervention and accept two analogue inputs, that would work.  (...but
someone would have to program it for me, or at least lead me through how
to program it.)  The 100Kc/s requirement isn't just fanciful
over-specification; this thing works on the signals that are well
outside the audio band and the 'scope needs to display them clearly,
despite all the audio clutter.  The H.F. signals are higher amplitude
than the audio but are in the nature of pulses and occur infrequently.
(The analogue scope has to be Z modulated from rate-of-change to
emphasise the pulses and avoid screen burn, but this wouldn't be a
problem with an LCD display.)


-- 
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk