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Author Topic: Cheap Oscilloscope  (Read 2258 times)
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Grenoble/Lyon - France
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Hi
I'm thinking about buying an oscilloscope, and I saw some USB probes, really cheap (like 50 euros on eBay).
I'm pretty sure those items are just a lost of money ^^

I just wanted to know if anyone have any good reference for cheap oscilloscopes, USB or not.
My goal is to be able to analyze signals encoded via NE5044 or LM1871 for RC toys transmission. If I can do more, it's ok ^^

Thanks

melka
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London
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Hi melka, how about free?

At the relativly slow data rates of an RC decoder, you could use your computer sound card with some freely downloadable software to display the waveform.

Have a search on google for: sound card oscilloscope
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Grenoble/Lyon - France
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That seems to be just perfect ^^
I'll check about the probes (I don't want to burn my soundcard) but I just tested quickly Virtins MultiInstruments.... That's nice ^^
I think I'll buy some of their probes, or I'll try to modify some regular oscilloscope probes.
Thanks mem
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Thanks mem.  I've been looking for an affordable oscilloscope solution for a few days.  After a bit of reading this seems perfect.  
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How about a scope based on Arduino: http://accrochages.drone.ws/en/node/90
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London
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Quote
How about a scope based on Arduino: http://accrochages.drone.ws/en/node/90

Nice!
Although a sound card would give better resolution (16 bits vs 10) and higher sampling rate (44khz vs around 10khz for the arduino),  but for relatively slow waveforms its nice to have a solution that's easy to customize. You would need to use a second board for the scope if the signal you wanted to measure was generated by an arduino, the scope board will be working flat out sampling and sending the data.

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What are the limits of using a soundcard as an oscilloscope? 5V, 12V?
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London
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Sound cards take an audio input. This means the voltage should be less than  ±1 volt on the auxiliary input, but check the specs for your card. A voltage divider is usually used to drop the voltage into that range and a 10k pot works well for me.
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Grenoble/Lyon - France
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I have to go check the electronics shops in my area and test it myself, but I think a simple classic Oscilloscope Probe with the x1/x10 selector might just work fine. There was a link posted, not so long ago, on this forum I think, a japanese guy who used this kind of cheap probe and just changed the BNC connector with a simple Jack.
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Denver
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Christian Zeitnitz has made a nice (free) sound card oscilloscope that's worth looking at -
http://zeitnitz.de/Christian/Scope/Scope_en.html .

As for limitations, besides the +/- 1V, my understanding is that the input signal must go through a capacitor on the sound card. This means no DC measurements and uncertain performance when viewing low freq. (<20Hz?) pulse streams. (From my experience with that scope.)

It would seem the Arduino scope would not need a coupling capacitor and not have that limitation, but I don't know.

Other than the frequency limitations common to sound card scopes, Christian's scope has often come in handy. It does a good job measuring frequency, and includes a wave form generator and other goodies.

FWIW

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The other downside to sound card oscilloscopes is that most cards are mono on mic input... so you only have channel on the scope.

I'd gladly pay $60 for a second channel when I'm working on stereo sound generation!
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Mathieu

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i have the rs232 version, $25, -- works great..
http://www.dataq.com/194.htm

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