Lab scopes

[signcrafter]

What all can you do with a lab scope that you can't do with a DMM? After reading the recent battery testing thread it talked about using a labscope to see things that you can't see with the usual battery testers or DMM.

What all can you do or see with a lab scope? What tests can it do?

Now the real question, is there a decent entry level scope that won't cost more than my last car!?

 

[ATTappman]

A scope displays voltage plotted against time, where the samping rate is very fast compared to a graphing multimeter. With a current probe you can also measure current. You can capture waveforms for various sensors like crankshaft and camshaft position sensors, O2 sensors, throttle position sensors, MAF sensors, etc. You can capture starter motor and fuel pump current waveforms. You can measure injector voltage and current, and ignition coil signal voltage. You can do relative compression tests. With the right accessories you can look at secondary ignition voltage patterns. A scope is a great way to learn about what's going on in a car. It does take some dedication, though. You have to put in the time measuring various components on a known working car before trying to use it on broken stuff.

You can get cheap Chinese handheld scopes for a few hundred dollars. You can by better quality used bench scopes for about the same or less. But the best option is to buy a Picoscope automotive kit. The starter 2-channel kit is $900. Adding some essential accessories to that is another $300 or so. I don't know how much you paid for your last car. When I bought a Picoscope, the expense depressed me for a week or so because it was half the value of the old car I tinker with. But all that faded away once I got the thing and started using it. With a scope and some self-study your diagnostic capabilities will expand greatly. If you work on cars as a hobby, it will make your hobby more fun. Whether it's worth the expense is something only you can decide.

By the way the Picoscope software comes with a program to do the battery test described in the other thread, although it doesn't spell out exactly what criteria it's using to declare the battery dead or alive. But you can examine the data and use your own criteria.

 

[Danglerb]

Scopes show input vs time, some capture one time events, others only show things that repeat. If you think you need one and you don't have one, fair chance you don't need one.

Prices vary, but tablet based scopes are constantly getting cheaper. Something like a Fluke is I think around $500, but Velleman (something like that) is $200 or less. Larger real lab scopes are cheap, but larger and older, and not with simple instructions for automotive use.

 

[FiendFX]

Picoscope is best choice but pricey. Lab scope is much superior then a DMM.

 

[richfinn]

I would add to that "Its a window" into combustion chambers/electric motors/pumps/ECMs/Injectors/ignition coils.......so you can see whats happening from the inside.

 

[AV tinker er]

I would recommend you watch some of "ScannerDanners'" videos on youtube. He shows you many differences where a DMM can fall short. And he is an electrical genius.

 

[Toolhorder]

For the price of that picoscope and accessories you can get a USED Snap-on Vantage pro and be way ahead of the game.

 

[FordExplorer]

Somewhat considering getting one myself. There is a snap on counselor 2 scope on the cabinet with accessories for $100 on craigslist near me. Is this something that an average person working on cars to keep them going should look into?

Sorry, didn't mean to hijack the thread.

 

[Danglerb]

I'd say no, nothing on a post points car needs a scope, sometimes its handy to "tell you more", but you can swap out a lot of parts before a scope pays for itself.

Good portable scopes, maybe even smart ones targeting automotive well get better and cheaper every year.

 

[joecon]

If you want to know what is going on in side a car inorder to know what is
wrong and fix it. You need to learn how to use a scope. If you dont care what
is wrong you can throw parts at it and geuss what is wrong and get good at that.
Knowing how to use a scope means you know how the parts you are checking
work.You understand how each system works with each other and all work together.
It is the sign of the top of the profession.

 

[Danglerb]

If you want to know what is going on in side a car inorder to know what is
wrong and fix it. You need to learn how to use a scope. If you dont care what
is wrong you can throw parts at it and geuss what is wrong and get good at that.
Knowing how to use a scope means you know how the parts you are checking
work.You understand how each system works with each other and all work together.
It is the sign of the top of the profession.

What I don't care about is the nature of some common parts failure, once I know its bad its going to be replaced. If no one had ever worked on this type of car before, then great lets study it, but when I know of 20 other of the same model with a similar issue, I prefer to cut to the chase and replace the bad part.

What specifically is it you are finding the need to put a scope on to test?

 

[MrMark]

Here's a perfect example of why you need a lab scope. My Mercedes had a problem with the accelerator pedal value sensor OR the throttle body throttle blade position sensor. The code that was set did not differentiate between the two. The scanner usually just points you in the general direction; many times it does show the answer. In my case, the glitch could have been on either part and it was way to fast to catch on the multimeter. The only way to not throw a part at it was a scope to find out which circuit was having the problem.

There are thousands of scenarios just like this one. If you know what you are doing and understand how the motor controls work the scope is the only way to avoid throwing parts.

 

[MrMark]

Here's an interesting thought on this: many times it may be cheaper for a shop to just take a crack at a problem by throwing a part at the problem rather than charge for the time to engage in serious diagnostics with a scope that they may not even have or know how to use very well. In my example above, the accelerator pedal sensor is around 120 dollars, and the throttle body around 400 dollars.

If I were paying someone to fix this it may be the most efficient route to forego any scope diagnostics and just try the new accelerator pedal sensor for 120. If it fixes the problem then correct guess; if not, then replace the throttle body. You "diagnosed" the car for 120 dollars. Many diagnostic situations are economically similar to this example.

 

[richfinn]

What I don't care about is the nature of some common parts failure, once I know its bad its going to be replaced. If no one had ever worked on this type of car before, then great lets study it, but when I know of 20 other of the same model with a similar issue, I prefer to cut to the chase and replace the bad part.

What specifically is it you are finding the need to put a scope on to test?

Well apart from the obvious sensor signals, its quick and easy to do a relative compression test with an amp clamp or cam-crank synch to see if a cam chain has stretched and its great for fuel pump current and alternator diagnosis.

I think you have to remember that since contact breaker ignition systems faded out oscilloscopes are now far more affordable and a lot smarter.

 

[signcrafter]

Well apart from the obvious sensor signals, its quick and easy to do a relative compression test with an amp clamp or cam-crank synch to see if a cam chain has stretched and its great for fuel pump current and alternator diagnosis.

I think you have to remember that since contact breaker ignition systems faded out oscilloscopes are now far more affordable and a lot smarter.

I was watching a scannerdanner youtube video on relative compression today. Holy cow does that guy know his way around a scope. I was lost for most of the video but he showed how the spark was happening on the intake stroke by using an amp clamp and a compression adapter hooked to his scope. It made me think that a scope is way more advanced than I am right now and they are pretty expensive. But I thought this same thing 10 years ago when I bought my first fluke and now I know my way around a fluke pretty good and how to figure out what I need to.

I'm just a DIYer and I think scopes are out of my price range. I can see where they would be handy for finging things like timing off misfires. You have good compression and have good spark and are getting fuel but still have a misfire. Here is the video I watched,

. Would there be any other way to figure this out without a scope? What other tools or tests could be done after you test for compression, spark, and fuel to see that the spark is happening at the wrong time?

 

[richfinn]

I was watching a scannerdanner youtube video on relative compression today. Holy cow does that guy know his way around a scope. I was lost for most of the video but he showed how the spark was happening on the intake stroke by using an amp clamp and a compression adapter hooked to his scope. It made me think that a scope is way more advanced than I am right now and they are pretty expensive. But I thought this same thing 10 years ago when I bought my first fluke and now I know my way around a fluke pretty good and how to figure out what I need to.

I'm just a DIYer and I think scopes are out of my price range. I can see where they would be handy for finging things like timing off misfires. You have good compression and have good spark and are getting fuel but still have a misfire. Here is the video I watched,

. Would there be any other way to figure this out without a scope? What other tools or tests could be done after you test for compression, spark, and fuel to see that the spark is happening at the wrong time?

How much would you be prepared to spend on a scope??

I bought Paul Danners book and its really good, try that first and see if its for you.

 

[MrMark]

what's the best price for the pico scope 2 channel auto starter kit? That's clearly the one to get.

 

[signcrafter]

How much would you be prepared to spend on a scope??

I bought Paul Danners book and its really good, try that first and see if its for you.

I don't really have a set price. I wanted to see how much scope could do for me to figure out a "value" for it. From what I have learned in the last few days I don't know if I would get my money out of a scope as a DIYer and also trying to figure out when and where to use one being I have no experience with one.

I don't mind spending money on quality tools. My theory is if tools and parts are cheaper than paying someone else then I'm ahead buying the tools. I've got many specialty tools I have only used once or twice but they have paid for themselves in my mind. But not sure I would see that kind of return on a scope. I'm sure there are times where it would be nice to have even being a weekend mechanic but for the most part I think the tools I have can tell me what the scope can for most diagnostics I do. From my limited knowledge of scopes and what they can do it would be far and few between when it would come in handy. Unless I"m missing something?

What is the cheapest I could get into one for? Is the a used market? If so what should I be looking for? What accesories would I have to have come with a used one?

 

[Toolhorder]

Well apart from the obvious sensor signals, its quick and easy to do a relative compression test with an amp clamp or cam-crank synch to see if a cam chain has stretched and its great for fuel pump current and alternator diagnosis.

I think you have to remember that since contact breaker ignition systems faded out oscilloscopes are now far more affordable and a lot smarter.

Damn I forgot about using that test to see if a chain is stretched. Thanks for posting I had a car last week I could have do this to confirm.

 

[richfinn]

I don't really have a set price. I wanted to see how much scope could do for me to figure out a "value" for it. From what I have learned in the last few days I don't know if I would get my money out of a scope as a DIYer and also trying to figure out when and where to use one being I have no experience with one.

I don't mind spending money on quality tools. My theory is if tools and parts are cheaper than paying someone else then I'm ahead buying the tools. I've got many specialty tools I have only used once or twice but they have paid for themselves in my mind. But not sure I would see that kind of return on a scope. I'm sure there are times where it would be nice to have even being a weekend mechanic but for the most part I think the tools I have can tell me what the scope can for most diagnostics I do. From my limited knowledge of scopes and what they can do it would be far and few between when it would come in handy. Unless I"m missing something?

What is the cheapest I could get into one for? Is the a used market? If so what should I be looking for? What accesories would I have to have come with a used one?

I think you could dip your toe in the water for $200-300 and maybe buy Pauls e-book for $50 or whatever it costs over there/and watch the videos.

Picos are fantastic but might be overkill for what you want.

If you just like tinkering and learning how stuff works try a used Snappy MT2400 Vantage graphing meter, I believe the American version had tech info included for what will now be fairly old cars.

You can get all the accessories at AESwave, cheap as chips

I found these looking pretty affordable.

http://www.ebay.com/sch/i.html?_sacat=0&_nkw=snap+on+vantage&_frs=1

 

[Skin]

I'd say no, nothing on a post points car needs a scope, sometimes its handy to "tell you more", but you can swap out a lot of parts before a scope pays for itself.

I'd disagree with that entirely. You can very easily lose hours every job you part swap, not to mention any parts that you just leave in the vehicle because you either cant or wont take them back out. But I guess that's okay because the customer can pay for your guesses. That's not a dig at you personally, but seems to be far too common of a practice in general.

Worth it for a home mechanic? Probably not. Worth it for a full time mechanic? Absolutely. You'd have to be incredibly obtuse to get into the business wanting to work on todays and tomorrows makes and models (other than grunt/gravy work of course) without learning your way around a scope. Its that critical.

 

[SpiderGearsMan]

scopes were real popular in the eighties ....

 

[Danglerb]

I have a lab scope, ie real scope, and it would not be a major issue to carry it to the garage and look at some signals, but accelerator pedals and throttle position sensors have slow moving analog outputs that I can easily monitor with my OBDII diagnostic software.

My 99 Lincoln has issues with the TPS and IAC, so I and the shop my wife uses when she is sick of waiting on me to fix it, have been trying to sort it out. Its intermittent, which makes use of a scope mostly a waste of time, but trivial to hook up to the OBDII and log behavior to catch it. PITA issue is that we have had a string of bad new parts, not DOA, but flaky within a few weeks.

Scopes are a dandy way to learn more about circuits, but imply a basic understanding that most will not have, so I am back to my original statement, if you don't have one, good chance you don't need one.

 

[MrMark]

You are dead wrong on all counts. Talking about slow moving analog signal shows lack of depth of knowledge. We are talking about a digital sampling system here with a fairly high sampling rate.

OBDII PID updating is likely not fast enough to catch that glitch and unless you have Star Diagnostic or equiv you aren't even going to get a PID on those separate signals. I don't know one way or another whether even Star Diagnostic has access to those signals. There are multiple circuits (and of different type eg, hall effect and pot) for each function so as to perform a rationality/plausibility check. There are 4 circuits total between two sensors. Circuits A and B for pedal postition and Circuits A and B for throttle position. There is one TPS value reported on a basic scanner (I don't know if Star Mark would report all four values but I do not have it and it's thousands of dollars and I doubt you have it either) and it is not updated very fast compared to the computers A/D conversion/sampling/rationality check.

You really have no idea what you are talking about here - this is a fly-by-wire, not some IAC turd. The computers rationality check and processing circuits sample those circuits way faster than you can look at them through OBDII generic (even if you could, which you can't).

I like how it is so trivial to you on that old ford but you can't seem to get it fixed - much simpler system too. Doesn't even sound like fly-by-wire with that old school IAC. Maybe you should lug out the old boat anchor scope from the old test lab and test it out.

You know what, the bottom line is that if I had Star Diagnosics maybe I could get the answers - but I don't because Star Diagnostics is a one car line specific investment and it's thousands of dollars. I also don't know that Star Diagnostics updates as fast as the circuits in question are chopped up (sampled/digitized) and tested by the computer or even if the Star reporting Bus updates as fast. With a lab scope I can solve the problem and fast too and across multiple car lines. I just intercept the problem circuit before the computer and go to work. This works for any car. So . . . for my particular circumstances, if I want to be able to fix multiple lines of cars, and cars in the future a labscope will get the job done across all those lines. A scanner to be useful for many things would require a factory level tool for each line to get me there - and there are many things a scope can get to like injectors and ignition that even the factory scanners can't help with.

 

[MrMark]

If I have learned one thing about scanners, it is that you need a factory tool or a VERY expensive one like the Verus for it to be an almost complete problem solver.

An inexpensive basic scanner with generic and enhanced coverage plus the scope in the right hands will solve the problem every time for any modern car. And no updates to worry about.

 

[junkman104]

I bought a Counselor II a few months ago with all attachments for 500.00 on CL. It has already paid for itself.

 

[Jeeper]

Mark - I may have missed it but what kind of scope do you have?

 

[FiendFX]

Snap on Vantage would be an affordable scope, although some may argue it's just a graphing meter but it's better than nothing. You can find them cheap on ebay.

 

[bcradio]

http://en.wikipedia.org/wiki/Fly-by-wire

 

[Skin]

Snap on Vantage would be an affordable scope, although some may argue it's just a graphing meter but it's better than nothing. You can find them cheap on ebay.

last time I checked they were going for like 1500 to 2000. Much better off putting that money into a pico setup. Faster and many more options/accessories. I really like the improvements they made in the scope interface on the verus but that's 10 grand.

 

[0.511MeV]

Prices vary, but tablet based scopes are constantly getting cheaper. Something like a Fluke is I think around $500

Missed a zero. I've been pricing a Fluke oscilloscope and the fast four channel versions are up around $5000.

 

[ATTappman]

If working on cars is not your profession, but you're doing it solely for economic reasons, then a scope is unlikely to pay off in money saved by not having to take your car to a shop. If working on cars is a hobby, and the cars were built after 1990, then a scope will make you better at the hobby if you spend the time necessary to learn to use it. Understanding and seeing for yourself the waveforms that all the various sensors produce and the actuators are driven by is a lot of fun, unless you're not interested in it. Once I overcame the fear of wasting money on it and actually got one, I was surprised at how much more fun working on cars became, and the money doesn't seem wasted at all. Learning and having more fun was my objective. If your objective is to save money, then probably you should do your own fluid changes and brake jobs and take everything else to a competent independent shop. As the cars get more technology intensive due to fuel economy standards, it may soon be impossible to do anything to your car without a factory scan tool, which the manufacturers may not even sell to an individual even if they're willing to spend the thousands it takes to own one and maintain the subscription. BMWs and MBs are already pretty much there.

 

[nanofrog]

For those interested, take a look at Rigol. Much more affordable than you might think, and they're quite decent for what they are. DS1000E series starts @ $329USD.

Not terribly large or cumbersome to carry around either (they offer a battery pack for some models). Some also offer optional CAN and LIN bus decoding if you need that.

 

[signcrafter]

This may be a stupid question but are the bigger "box" style oscilloscopes like this, http://www.rigolna.com/products/digital-oscilloscopes/ds1000e/, good for cars or do you need a handhelp type like the tool trucks sell for cars?

 

[FiendFX]

last time I checked they were going for like 1500 to 2000. Much better off putting that money into a pico setup. Faster and many more options/accessories. I really like the improvements they made in the scope interface on the verus but that's 10 grand.

That's the vantage pro... Vantage is only a few hundreds.

 

[PatJ800]

You have to figure out exactly what you want to look for and then you can decide if you need a scope. Even if you find a 30+ year old scope on Craigslist for $25 it is probably going to have a bandwidth of 50 mhz at least, and probably 4 or 5 times that. I am not an expert in all things automotive, but I would have a hard time believing that any gas pedal position sensor is going to output anything even remotely close to 50 mhz. You are deep in to radio frequencies by that point. I would be surprised to see any common automotive analog sensors communicating at 50mhz, let alone 200 mhz or 350 mhz. Who knows though, I could be wrong.

In my opinion you need to figure out exactly what specific thing you are trying to see/test and do a little research to see which tool is best for the job.

Scopes are fun to play with and interesting and if you get a good deal on a used one then it will not lose much value if you find yourself never using it and reselling it later. I got my first scope decades ago as a teenager when I was in to the then-uncommon world of switching power supply design and tinkering. I bought that scope used then and still have it and have never needed more as an electronics hobbyist. I have also never used it for any automotive application.

I would not buy the (probably Chinese) digital unit you linked. If you decide to go this route I would shop for a used Japanese or Taiwan CRT unit in the 20-year-old range. Just my opinion.

 

[Danglerb]

You are dead wrong on all counts. Talking about slow moving analog signal shows lack of depth of knowledge. We are talking about a digital sampling system here with a fairly high sampling rate.

OBDII PID updating is likely not fast enough to catch that glitch and unless you have Star Diagnostic or equiv you aren't even going to get a PID on those separate signals. I don't know one way or another whether even Star Diagnostic has access to those signals.

I fully agree with your last sentence. I have the Ford package from AutoEnginuity and it does it all just dandy including the sensor testing routines just like the Rotunda systems.

Throttle position sensor changes at the speed of your foot on the gas pedal, to me that is SLOW moving analog, and beyond that I see no merit to observing its dynamic behavior which should be no different from its static behavior so how fast the signal changes means nothing.

I still do not see the need for a scope. If I have a Bosch FI brain using a Bosch crank sensor, and I don't get a pulse to my injectors, I replace the crank sensor, then the brain.

Don't let me spoil your fun with the scope, but I learned all I wanted to know about waveforms from Hall sensors 30 years ago. If the FI brain doesn't like the signal, I don't care what it looks like on a scope, it doesn't work.

 

[nanofrog]

This may be a stupid question but are the bigger "box" style oscilloscopes like this, http://www.rigolna.com/products/digital-oscilloscopes/ds1000e/, good for cars or do you need a handhelp type like the tool trucks sell for cars?

11.93" wide, 6.06" high, 5.24" deep, and weighs 5.28 lbs.

So not really all that big. Set it on a cart of some sort, get it power, and go if you need one.

Handheld is more convenient, but there are compromises to do so. Particularly with the display screen.

Functionality wise, you get more bang-for-your-buck from a desktop form factor.

 

[MrMark]

I fully agree with your last sentence. I have the Ford package from AutoEnginuity and it does it all just dandy including the sensor testing routines just like the Rotunda systems.

Throttle position sensor changes at the speed of your foot on the gas pedal, to me that is SLOW moving analog, and beyond that I see no merit to observing its dynamic behavior which should be no different from its static behavior so how fast the signal changes means nothing.

I still do not see the need for a scope. If I have a Bosch FI brain using a Bosch crank sensor, and I don't get a pulse to my injectors, I replace the crank sensor, then the brain.

Don't let me spoil your fun with the scope, but I learned all I wanted to know about waveforms from Hall sensors 30 years ago. If the FI brain doesn't like the signal, I don't care what it looks like on a scope, it doesn't work.

You don't get it. It's not how fast you move your foot, it's how fast the system samples the signal. I have no idea what you are talking about with that story on static and dynamic behavior. That is a real head scratcher. When you press on the gas and go to full throttle the computer is acquiring that signal in digital form very fast, eg. many times per second. Importantly, to catch a glitch that causes an error condition in the throttle control software you need to oversample the signal with your test equipment or you will never find the transient. I tried to catch it on peak detect on a good Snap-on multimeter and I could not despite the computer putting the car into limp during a full throttle snap. The multimeter could not catch the transient.

You autoenginuity while "dandy" for your Ford would not be so dandy for my car and would not be fast enough for this.

I'm glad you learned everything you need to 30 years ago, but I don't work that way as I am constantly learning, and I don't just throw parts like that.

 

[richfinn]

I fully agree with your last sentence. I have the Ford package from AutoEnginuity and it does it all just dandy including the sensor testing routines just like the Rotunda systems.

Throttle position sensor changes at the speed of your foot on the gas pedal, to me that is SLOW moving analog, and beyond that I see no merit to observing its dynamic behavior which should be no different from its static behavior so how fast the signal changes means nothing.

I still do not see the need for a scope. If I have a Bosch FI brain using a Bosch crank sensor, and I don't get a pulse to my injectors, I replace the crank sensor, then the brain.

Don't let me spoil your fun with the scope, but I learned all I wanted to know about waveforms from Hall sensors 30 years ago. If the FI brain doesn't like the signal, I don't care what it looks like on a scope, it doesn't work.

Sorry. Got agree with MrMark, your serial connected scan tool is not fast enough to trap a TPS glitch as the refresh rate is way too slow, even if you have narrowed your PIDs down to just that sensor.