MrLexse

I've been thumbing through the test procedures in the WSM's, and I've run across a few tests calling for the use of an oscilloscope. I don't own one and would prefer not to skip these tests. Is there an alternative method or should I pick up a used one? I've got a local who has a Snap-On Counselor with the manuals etc. for $200. What do you think? Thanks

Chris

If you have a laptop I would go and buy a USB Oscilloscope, you can pick up a basic one for $100.

Chris

Lizard928

I got one on ebay awhile back for $20

Alan

There is no subsitute for an oscilloscope - however USB/PC and cheap used ones are adequate - car tests are all low frequency so just about any model will suffice. Calibration is normally an issue and this affects older cheaper units more - but - for auto use you rarely care about the voltage levels to any great accuracy anyway... so its easy to use just about anything that is functional..

Alan

Mike Frye

__ A little OT, but what tests require an O-scope?

sublimate

Certainly very useful for diagnosing fuel injection problems.

Alan

Timed pulses - like spark (inductively coupled) or injector timing plus any rotating sensors: rpm/crank position, ABS, PSD are best diagnosed in operation with an oscilloscope

Alan

Vilhuer

There is practically free alternative of using laptop sound card and free software. Just need little wire and connectors. See for example:

http://zeitnitz.de/Christian/Scope/Scope_en.html

RngTrtl

WARNING!
This is a very good alternative and very cheap; however, if you plug 12 volts dc into your sound card you will cook it almost instantly. A voltage divider must be hooked up so you do not ever exceed approximately 1 volt dc input into the sound card and also limit the current flow sufficiently. I have used 11k ohm and 1k ohm resisters with excellent results.
END WARNING!

UKKid35

I'm not sure what voltage a soundcard would be happy with, up to 1V perhaps?

If you need a low cost USB solution perhaps this is an option (up to 5V) http://myweb.tiscali.co.uk/pcscope/scopedem.htm

UKKid35

Sorry - didn't see your reply!

davek9

Thanks for the link this works great (for free), and now to build the probes!

Your right about the +12v DC into a sound card input!

This was taken from the web site:
"For external sources care has to be taken, not to exceed the voltage range of the inputs. The range is usually only ±0.7V !!
If higher voltage need to be analyzed, a voltage divider has to be used. Additional protection diodes are recommended in order to avoid any damage to the sound card and to the computer.

What watt resistor would you recommend (1 watt)?

Thanks,

Dave K

docmirror

Use this:

http://cgi.ebay.com/100MS-s-PC-Based...QQcmdZViewItem

it comes with everything you need, and is easy to setup. don't skip some of the steps if you're troubleshooting a waveform problem.

derporsche928

Doc,
Am I understanding this correctly....?
This just saves a sample reading and then you hook it to your computer to read....?
(I'm just a little leery of frying my laptop with the other above mentioned options....)
Best,

sublimate

Using the resistors he suggested you would only need to dissipate 0.012 watts.
NOTE: you need both resistors for a voltage divider. Not sure if your use of the singular was just a typo.