Does anyone here use software/hardware to utilize their PC as an o-scope? Something like this Oscilloscope for Windows

 

There are a couple of issues with this. First, the 20KHz bandwidth. That means you can look at audio signals, but not much beyond that (no radio, not your computer, etc.) The other problem is that your sound card most likely has a capacitor on the inputs (at least the old ones did, I presume the new ones do to). That means that you won't be able to look at DC values, such as a 12V battery.

It will work for something slow like the injectors on your car, but may not work for the map signal. Slow moving signals like the map signal will drift towards 0 and you won't know for sure what is going on if you have the capaictor on the input.

Hope that helps.

 

What about a Pico unit? It is a hardware unit that plugs into the pc. Only a two channel scope, but would that do? I've seen one in use, and they are good enough for autotive use. The example of the MAF signal - no problem. Just an Idea.





http://www.aeswave.com/products/Product.asp?i=267

 

Thanks, that does help.... I was unaware of the capictor issue on the sound card inputs. I don't know for sure, but I'm assuming that software uses the Mic or Line In to input the signal. I wasn't necessarily limiting my question to that particular software but was rather just using it as an example. I was looking more for info about software/hardware of that type that would allow me use a PC as an o-scope. I'm not the most proficient person in the electronics field.... more like I know enough to be dangerous... but I'm trying to learn. I don't have big $$$ to shell out for a fancy o-scope and was looking into a low-buck alternative to get me started.

 

i havent ever looked, but perhaps someone makes a PC card that is setup to do it? then you wouldnt worry about sound card caps or anything else fudging the input.

 

There are lots of such devices out there. Go to the Nuts and Volts website, click on advertisers links and search for test equipment. There are two or three vendors there (seems like there are more listed in their paper magazine). I used one of these a number of years ago, and it worked OK. Not nearly as nice as the scope I had, so I used the scope instead. However, I suspect they have come a long way since then, and they probably work much better. A point of reference is that many of the newer Tektronix scopes are actually built on Windows 2000 or XP, and are just using specialized hardware (very good specialized hardware of course) to collect the signals.

 

Which one did you use?.
All I see is BitScope, and it seems kinda pricey.
I had one from Radio Shack that was just right, when it worked and it was like $150 with all the bells and whistles.

With audio signals being so much higher freq., then what we're looking at, shouldn't an audio card, not have much capacitance?. Maybe a quick explain?.

 

I would think that the caps are used on the input to get rid of noise from local ac power lines. Although the input voltages are already pretty high . All in all I don't think it's such a good idea using a PC as an oscope but if that's all you have, that's all you have. I'm just spoiled.

 

The capacitors are in series with the input. That is, they are not there for noise reduction (there are probably some of those too though). They are in series to block DC. So, if you put a DC signal, say 12V, on your sound card input, the capacitor will slowly charge, and so what you will see on the display is an initial value of the 12V that will decay down to zero over a few milliseconds. So, say you wanted to look at your map signal. If you hold the throttle still, you will see the MAP value decrease to 0V, even though the MAP signal stays still. If you want to look at something that is changing all the time, like the injector signals or the spark signal, it will work better as long as all you care about is the edges. If you are interested in the levels, it will lie to you just like it would with 12V. If you want to look at sine waves, such as audio, the sound card is great (duh!)

Hope that helps.

The card I used as a scope was a fairly expensive card as well, and was an ISA card (this was about 10-12 years ago).

I'll look in my Nuts and Volts magazine tonight and see what I can find.

 

In the professional auto repair industry, the Pico Scope is regarded pretty highly. Us automotive technicians like to see a nice, big, clear display such as a PC monitor. There are MANY sub $1000 scopes out there that are specifically for automotive use, and from what I've seen, not many of them are better than the inexpensive ($400) scope module I got for my Handspring Visor. Sure, the screen is small, but my eyes are still good, and I can put a snapshot up on the PC if I need to.

What sort of stuff are you wanting to do? The best scope will depend on what you need it to do (signals you will be looking at).

My inexpensive PDA scope works well for most things such as injectors, fuel pump current pattern, primary ignition current, injector current, on and on.....the one thing that I found it not sop good at is O2 snesors, and that's only because at a long timebase, it takes too long for the display to update.

There are a bunch of great scopes out there, and which one works for you is whatever one you try out and like. The bad thing is that it is difficult to try them all out before buying one!

 

The items you mentioned are the types of signals I'd be looking at. I did see the Pico website and it looks like a good setup by a tad pricey for my limited budget. For that money or less, I saw several 2 and 4 channel o-scopes on ebay but they did look to be older. The real problem is, I don't know exactly what features I should be looking for or what features constitutes a "good" scope. Got any suggestions?

 

Did you check out AESwave.com? They supply all kinds of scopes for the automotive industry. I use an old Sun Ls2000 most of the time at work. It is only a two trace scope, but does a very good job. I've seen them as low as $400. You can use software from Metratek to display all your saved waveforms. Or use something like the AESwave software. Usually for automotive if it has glitch capture it will do. Or something like that. It is like oversampling. Sampling at a higher rate than is needed. It lets you see what the older computer type scopes wouldn't. I look at igntion waveforms all day, and I still use an old analog scope because it catches all the little things. And those are usually the things you are looking for. A lot of the Pc based scopes have to put the data threw a cable before displaying it. There is a lag, and missed information.
Like I have been hearing people say, "Pick the scope for what you want to do." I use scopes all the time, and I have different ones for different jobs. I'm going to have to check out one of those PDA scopes now. Nice small package, and I bet it does better on the batteries than my LS2000.

Good Luck,
Marcello

 

Check testntools . They have a bunch of scopes there, for as low as $269. You need a scope with a bandwidth that is at least 10 times the highest frequency you want to look at. However, it is important to remember that when you are looking at pulses or square waves (like ignition signals or injector signals), the frequency content of these is quite high, much much higher than the frequency of the pulse or squarewave. For the automobile, 20MHz will work quite well. 2 channels is probably as much as you need.

Chevota, there really isn't any discernable delay caused by the cables, electricity travels at about 1 foot per nanosecond (rough number) through cables, so if you have a 20 foot cable, you are talking about approximately 20 nanoseconds. Not much happens in a car in 20 nanoseconds. What you are seeing is processing time. All digital scopes have this problem, at least at their highest speeds. They can't process and display as fast as the signals change, so they capture for a while and then display for a while. Even analog scopes will miss stuff during the retrace time. It's just a fact of life. The only way to help with this is to have a very large memory buffer on a digital scope that allows you to capture lots of data and then process it.

 

also, on a totally diffrent route, highschools and colleges tend to sell their used equipment really cheap....

 

Not my school. We can use the equipment for free since I'm on a student project BUT all old equipment go into the "oscope musium" which is basically a bunch of shelfs full of crap in an open low bay area of the ME building. It's kind of cool but man do they need to let go of the past and move on.

 

well that sucks.

goto someone with some power in the system and tell them about it..

if you leave enough hints about how they can get money for stuff thats just trash to them, theres a good chance you might get the ball rolling with stuff...



on a side note, i did just that with radioshack... when people return stuff saying its broken, but the part isnt worth the techs time to fix, i got them to donate the broken items to the schools electronics lab to pratice fixing... (example: spending $30 in time on a $50 radar detector that they make $20 off of is counter productive)

but because i was a teachers assistant (read: apple polishing suckup) i got first pick.... and alot of that stuff wasnt broken...

 

OK, I will agree with what you are saying. I have used some pc based scopes, that don't simply use wire. They have an ethernet card as part of their hardware, and use a cat 5 cable to connect to the computer. I was referring to this type, and should have been more specific. You would be limited to the timebase of the ethernet, and the system I was using was base 10. That was fine with a single trace, but much more and the sampling would go way down.
I have been looking for a scope with exactly what you are saying. I want a large storage capacity. Leave the car running with the scope hooked up, walk away, car does it thing whatever that is, come back and scan through the saved data to find the problem. I hate waiting for a problem to occur, because it always happens when I turn my head. That is the big thing with a scope, it is a great tool only if you can catch the problem happening!
I am going to disagree with the idea that a single or dual trace is good enough. I have a dual trace, and quite often want a third trace. Usually a fourth is rarely needed, but would be nice. Many times looking at signals between the ecm and the ignition module I need to look at three lines.....bypass, hi ref into ecm, and est line to module from ecm. I am surprised how often this comes up with trouble cars. There will be no sign of problem, and then suddenly the car with start loosing cylinders, or cut out. You need to see where the problem started. The ignition or the ecm/pcm. Just my opinion. And two two-trace scopes are not the same thing. Need all the channels sync'd off the same base signal.

 

Sounds like you need a datalogger. B&B makes a neat unit that I am using for my wide band O2 sensor. With this, and a laptop with a serial port (or USB port and USB to serial adapter), you can log lots of stuff. However, it is kind of slow, and you will need to use resistor dividers to get the 12V signals down to 5V.

 

If you shop around, a decent old scope can be had for under $100. I have a nasty old 1970's heathkit 5mhz scope that still works fine. It is big, it only does one trace, but it works! (and when it doesn't I fix it )

This also mgiht be kind of stupid, but a camera hooked to a vcr works good for logging on a budget