Author Topic: Digital storage for analog Oscilloscopes.  (Read 6345 times)

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Offline firewalker

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Digital storage for analog Oscilloscopes.
« on: October 14, 2011, 12:08:03 pm »
Someone asked me today what is the point of single-shot trigger in analog oscilloscopes (he didn't knew about oscilloscope cameras e.t.c.). Bla bla bla... Is there a digital storage for analog oscilloscopes? Like an add-on between the bnc connectors of the probe and the input.

Not something "crazy", just for sigle-shot events from a PSU etc.



Alexander.
« Last Edit: October 14, 2011, 12:35:53 pm by firewalker »
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alm

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Re: Digital storage for analog Oscilloscopes.
« Reply #1 on: October 14, 2011, 02:16:28 pm »
That would basically be a complete DSO, except the output would have to be converted to X,Y,Z instead of LCD. It would need amplification, attenuation, triggering and sampling. The LCD is not exactly the most expensive or complex part in a modern DSO. Getting a crappy low-bandwidth/voltage DSO would probably make more sense.

Analog storage was the old way of doing it, they used a special CRT that would retain the charge from the trace for a certain amount of time. This technique is inferior to a DSO, though, and completely obsolete, as opposed no normal analog scopes.
 

Offline david77

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Re: Digital storage for analog Oscilloscopes.
« Reply #2 on: October 14, 2011, 02:39:57 pm »
I think Elektor published a circuit that did that back in the 80ies. That was a proper TTL grave though with just a few bytes (bits?) of sampling memory and almost certainly much worse than any of the cheap toy DSO's of today.
 

Offline firewalker

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Re: Digital storage for analog Oscilloscopes.
« Reply #3 on: October 14, 2011, 03:03:45 pm »
Speaking for today, yes it wouldn't worth it. But analog oscilloscopes was the way to go several years ago.

Alexander.
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Offline McMonster

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Re: Digital storage for analog Oscilloscopes.
« Reply #4 on: October 14, 2011, 03:07:05 pm »
There's also different approach to this topic.
 

Offline david77

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Re: Digital storage for analog Oscilloscopes.
« Reply #5 on: October 14, 2011, 03:09:43 pm »
As I do not own a DSO this is the way I do it, today with digital cameras it is easier than in the days of Polaroid film but it is still a bit annoying  ::).
 

alm

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Re: Digital storage for analog Oscilloscopes.
« Reply #6 on: October 14, 2011, 03:18:00 pm »
Triggering it within milliseconds to record a single shot trace might be tricky with cheap cameras, though.
 

Offline tekfan

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Re: Digital storage for analog Oscilloscopes.
« Reply #7 on: October 14, 2011, 06:03:54 pm »
Triggering it within milliseconds to record a single shot trace might be tricky with cheap cameras, though.

It's actually not that difficult. All you have to do is to set the camera to a longer exposure time.

How to get nice pictures off analog scopes:
http://amplifier.cd/Technische_Berichte/Photographie_Oszilloskop/Foto_Halterung.html

There's also different approach to this topic.

And yes that is the right and probably most practical approach to this problem.
One can never have enough oscilloscopes.
 

alm

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Re: Digital storage for analog Oscilloscopes.
« Reply #8 on: October 14, 2011, 06:12:43 pm »
Long exposure works as long as ambient light levels are low or the hood is light tight. It also requires the trigger to occur within a few seconds of triggering the camera, i.e. it should not be a rare event.
 

Offline Rufus

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Re: Digital storage for analog Oscilloscopes.
« Reply #9 on: October 14, 2011, 06:52:41 pm »
 

Offline EEVblog

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Re: Digital storage for analog Oscilloscopes.
« Reply #10 on: October 15, 2011, 12:21:49 am »
Yes, there have been a few magazine projects along these longs before PC based DSO adapters came along.

Dave.
 

Online NiHaoMike

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Re: Digital storage for analog Oscilloscopes.
« Reply #11 on: October 15, 2011, 03:57:53 am »
It's possible to do that with a CCD used as an analog shift register. If you're going to bother converting to digital and storing it, you might as well just stream it to a PC. There's little point in using an old fashioned boob tube nowadays...

An interesting hack would be to hack an old hard drive to act as an analog circular buffer. Just secure the heads in one position (easiest way is to apply a current to the linear motor), then have it record until a programmable time after a trigger, in which case it switches into playback mode.
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Offline elCap

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Re: Digital storage for analog Oscilloscopes.
« Reply #12 on: October 15, 2011, 02:32:06 pm »
Iwatsu is making a 1GHz analog oscilloscope using a CCD connected to a CRT, and then display the traces on a LCD.
Tequipment has it, currently on sale, only $28k! :o
http://www.tequipment.net/IwatsuTS-81000.html
 


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