I figured I would post this here for those of us who are not quite so fortunate to be able to afford high power multi meters, amp meters and oscilloscopes.

Finding an oscilloscope that you can use is easy and cheap enough, but the limiting factor is the amount of voltage and or current it can handle. I downloaded an oscilloscope program that works through your sound card.

You can find it here: Virtins Technology: Turn a PC into Virtual Instrument - Home

There is a free seven day trial. The basic oscilloscope is 25$ US, but they have spectrum anylizer and function generator upgrades for up to 50$ US.

I used this a little bit, and it seemed to work OK, though I haven't been able to test much of anything in 7 days without proper equipment. The thing you have to worry about is frying your sound card in your PC, or even hurting the PC itself. They have instructions on a limiting circuit but I was worried about wave clipping/deforming and accuracy issues with it.

I also wanted to be able to test things well above the voltage my comp can handle, as well as current.

With the introduction of Voltage dividers and Shunts, you can work out circuits that would allow you to measure much higher voltages/current without burning out your PC. All that it would take is a little math.

Voltage Dividers

Using known resistor values, you can measure the voltage drop between two of them. You can enginer this to create an known voltage drop or division ratio.

The Voltage Divider Rule

Now the only thing I wasn't able to verify (at least in the little bit of research I've been doing) is weather a simple resistance voltage divider can be used for both ac and DC. I've come across sites that say yes, and others that say you have to use an induction or capacitance divider.

The other thing I would be concerned about is the accuracy of any divider circuit.

Shunts

Shunts are used to measure Amperage, using ohms law you can use a shunt (a piece of material with a known resistance value) and measure the voltage drop across it and again with a little math you get your amperage as well

Make a Shunt Resistor - Electric Circuit


I would encourage others to add there ideas or mods for these cheep skate shortcuts as well as anything way or process that will make these as accurate as possible. These tools will make it easier for others to measure and document their results.

Also, post any other ideas/resources to make this even better!

http://www.xs4all.nl/~jwasys/old/diy2.html

http://www.johann-glaser.at/projects/DSO/

http://www.chocbar.demon.co.uk/

http://www.geocities.com/lptscope/

http://alternatezone.com/electronics/dsoamk3.htm

http://home.planet.nl/~m.f.hajer/scope2k4.html

http://www.transmic.net/scope.htm

http://www.nbb.cornell.edu/neurobio/land/PROJECTS/VideoScope/

http://jonw0224.tripod.com/ppmscope.html

http://scopeonpc.tripod.com/index.htm

http://www.soundtechnology.com/LAB432.html

http://hacca.altervista.org/Detailed.htm

Sweet links!

I've already set up my sound card for the Virtins oscilloscope and now: http://hacca.altervista.org/

It's free, now thats really cheep! Its also fully loaded, even more so than the full version of Virtins. Now I'm glad I didn't shell out the money to buy it.

Now I just have to set up some voltage dividers and I can test anything I need!
Thank you very much for the links!

Yeah problem with sound card as an instrument is that you cannot measure anything above few volts without voltage protection in front.

In my case I prefer to have stand-alone unit that can be moved around and work without a PC hooked up.

I'm going to build and test the following circuit. It's based on PIC so that'll make it even more fun:

semifluid.com » PIC18F2550 KS0108 Graphical LCD Oscilloscope

If you check that link he's got lots of more fun stuff...

It's really surprising how many of these projects seem very doable. I've got a little electronics background (very little, but some) So tinkering with this stuff wouldn't be hard but I have little or no programing background so the more complicated programing projects are likely out of my league. Still its good information for others who have a greater understanding of this stuff.