Beginner scope for car repair - Page 1
Forum section: electronics / repair

author: Rust
author_rank: Newbie
timestamp: March 13, 2013, 07:32:01 pm
content: HelloI am looking for a small oscilloscope to measure sensors in my car ... Nothing elseI've looked at Velleman HPS140i and ARM DSO203 Nano V2...Velleman:http://www.vellemanusa.com/products/view/?country=us&lang=enu&id=525377PSO203 Nano V2:http://www.sainsmart.com/sainsmart-arm-dso203-nano-4-channel-mini-v2-quad-pocket-digital-oscillo-scope.htmlWhich of them would you recommend for my needs?It should be noted that I have absolutely no sense, on Oscilloscopes and therefore do not seek any advanced...Thank You Very MuchBest RegardsHenrik Nielsen - Denmark

author: brainwash
author_rank: Frequent Contributor
timestamp: March 13, 2013, 10:46:18 pm
content: Worst case: PicoScope, if you cannot afford the cheapest bench DSO you can buy. A 12V->220V supply can be bought for a few dollars but anyway most new entry-level bench DSOs support battery operation.DSO Nano and the Velleman would be a waste of money, you will not be able to set up the triggers nor see the ignition characteristic.http://www.picoauto.com/automotive-library.html#case

author: warywolfen
author_rank: Newbie
timestamp: March 14, 2013, 02:45:00 am
content: I'm not very knowledgeable regarding modern cars, so I don't really know what capabilities you need. However, I would definitely check out Ebay and other online auctions. I've gotten good test equipment that way for much less than the new price.

author: Rust
author_rank: Newbie
timestamp: March 15, 2013, 07:33:39 pm
content: Hello again and thanks for Your inputA Bench Scope is too advanced for me ... I'm just a panel beaterI do not need a trigger function and use advanced features ... I just need to measure slightly different sensors such as Lambda and air flow meters...I do not know how to use a scope yet and have never tried it ... therefore it must be simple ...However, I can use an ordinary inexpensive multimeter but this does not update fast enough to measure lambda for example.Do this any difference whether I should look for other scopes?A bit more expensive than the former are those which are to usb:http://www.vellemanusa.com/products/view/?country=us&lang=enu&id=524708http://www.picotech.com/handheld-oscilloscope.html2104http://www.picotech.com/entry-level-oscilloscopes.html2204I'm just afraid that they become too advanced for me :/And then there is the problem that I have my PC in the workshop to use themBest RegardsHenrik - Denmark

author: kripton2035
author_rank: Super Contributor
timestamp: March 15, 2013, 07:55:48 pm
content: why dont you get an obd2 reader ? it's enought to read sensors like lambda or airflow ?

author: kfitch42
author_rank: Frequent Contributor
timestamp: March 15, 2013, 08:22:12 pm
content: I would suspect that any of the PC-based scopes would be a bad idea for use with a car.1) It would seem to be quite inconvenient to have a PC in your garage2) The ground lead on the probe will be connected all the way back to the ground pin on the wall socket. I am just a noob, but I suspect that could cause problems.Although I guess a laptop running on battery might be OK.A quick search on "da bay" says you could snag a fluke "scopemeter" like the one in a recent teardown video for a few hundred dollars. So, I suspect one of the two mentioned in the first post would be a cheaper (and still good-enough) solution.

author: Rust
author_rank: Newbie
timestamp: March 15, 2013, 08:35:25 pm
content: Old cars don't have the obd2 connectorI also believe that the first two would be ok for my needs ... Especially the DSO, though I think that Velleman's look more simple.Actually, I just see the curves look right ... I do not even have data values ??on all cars

author: brainwash
author_rank: Frequent Contributor
timestamp: March 15, 2013, 10:15:08 pm
content: Like i've said, the cheapest one is the picoscope. I have diagnosed ignition and charging problems with a Tektronix, but i suspect i is outside your prive range. If you are ok in that job you should get the minimum recommended. But you already seem to have your mind set on the cheapest stuff.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 16, 2013, 03:05:49 am
content: It all depends on the degree of convenience you need.A normal (analog or digital) bench scope will probably need to be run off the mains,with a long extension cord,which may be a safety hazard.I've looked at auto sensors,pulsed signals out of the ECU,etc on a 1988 Ford with an old BWD 'scope,& with a portable Tektronix DSO/DMM of 1990s vintage.They both did the job OK.Since I ditched the Ford & got a Toyota,I haven't had the need to do these tests!

author: M0BSW
author_rank: Frequent Contributor
timestamp: March 16, 2013, 09:08:07 am
content: UT81B portable Scope Digital Multimeters 8M bandwidth eBay

author: mc
author_rank: Regular Contributor
timestamp: March 16, 2013, 12:18:18 pm
content: For the majority of diagnostic work on vehicles, you don't need a scope.A good quality multimeter will diagnose most electrical faults. I deal with lots of diagnostics, and it's rare that I use a scope. Usually by the time the scope is pulled out, I'm looking for faults I'm only ever likely to see once.However, if you do get a scope, you want something with a big screen. For the majority of work, you need quite a wide trace, as you need to see a large sample to pick up faults. Off course the same can be done using a storage scope, but seeing the fault in realtime is better.

author: brainwash
author_rank: Frequent Contributor
timestamp: March 16, 2013, 01:01:38 pm
content: I diagnosed a faulty coil once by using the scope. The bike has been through a lot of mechanics, each one more 'skilled' than the other, charging more per hour just to clean the carbs again and again. The symptoms was that the bike was misfiring under load and medium/high rpms, so it was acting almost like a power limiter. Every part was swapped with another one and still the stuff was happening.Long story short, this type of diagnose could only be done with a storage scope, because you cannot keep the bike at 9000 rpm while you set up your scope to reliably catch the trace. You also need to see how with increasing rpms the misfiring happens as the chamber fills up with richer fuel.Yeah, the faulty coil was swapped with another faulty NEW coil, this is why it was hard to trace. Everyone blamed the CDI (swapped also) because it's a big black box that nobody understands, so it must be broken.

author: mc
author_rank: Regular Contributor
timestamp: March 16, 2013, 02:33:18 pm
content: Could of done the same with a multimeter set to frequency attached the LT side, inductive clamp rev counter on the HT side, and monitoring to see where the pulses get lost.However most people wouldn't have an inductive rev counter, so it's a case of using what tools you have available.One job I can think of where a scope was the only accurate way to provide a diagnosis without major dismantling, was a vehicle that started surging/misfiring above about 3000rpm, without registering any fault codes. Below 3000rpm, it drove perfectly. Somebody else had tried swapping various fuel system components, however nothing made any difference. Using the diagnostics, I could see the fuel pressure was surging, however more interestingly, the RPM value was jumping at higher revs. Even on something surging, the RPM should never jump, it should transition relatively smoothly between speeds, with the only jump being the lag in the diagnostic display.I tried swapping the crank position sensor with no effect (5 min job with another identical vehicle), but again no difference. So out comes the scope (one that comes with Ford's IDS system), and it's immediately obvious there's a mechanical fault.For crank position, most engines use a toothed ring, which generate an AC signal in an inductive sensor, which is then fed back to the main ECU for processing. The toothed ring will have a reference tooth, which is larger than all the other teeth. For example a 60 minus 1 pattern, would have 58 identical teeth, and then instead of having another 2 identical teeth (to give the 60), the gap is missing (hence the minus 1), resulting one large tooth. On a scope trace, this should produce a trace of 58 identical sine like pulses, then one large +/- pulse with an almost flat spot where the missing tooth is.However instead of a nice row of almost identical pulses, this engine was generating pulses of varying voltage, indicating there was an issue with the toothed ring. On this engine, the toothed ring was on the flywheel, and it turned out that it had just had a new gearbox fitted because the old one had disintegrated. Upon removing the gearbox, some of the debris had got caught by the flywheel and bent some of the teeth.There are other jobs where a scope is nice, like dealing with CAN bus faults, but I've done the same using a multimeter. Having a scope showing a trace on a big screen is nice, as you can see at a glance what is happening, but measuring the voltage on a multimeter usually does the same job, it's just not as easy to see/read.

author: M0BSW
author_rank: Frequent Contributor
timestamp: March 16, 2013, 03:47:34 pm
content: When my ford had a cambelt sensor go sick the non ford garage used a dianostic box on it , and let me see what it does fasinating stuff, I also found out my car had no other faults, I said non ford garage as the one I used fixes porsche, the ford dealer wanted £119.00 plus VAT, for diagnostic only plus parts & labour, the porsche garage where my ford is serviced wanted nothing for dianostics, cost was the sensor and 1/2 an hours labour approx £30.00p

author: brainwash
author_rank: Frequent Contributor
timestamp: March 16, 2013, 04:41:44 pm
content: The thing is, scopes have come down a lot in price and it's often cheaper and more flexible to buy a DSO than to buy a one-time specialized tool. It does have a steeper learning curve though.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 17, 2013, 04:02:13 am
content: As an Electronics person,I tend to grab a 'scope!The old EA Falcon had an intermittent problem where it stopped running,but would restart after a while.The car gurus muttered darkly about a "computer problem",but couldn't find anything----such is the nature of intermittents!Eventually,it morphed into a "won't start" problem,so it was try again with a "Mobile mechanic" or do it myself.I borrowed the Tek portable DSO from work,& backprobed the ECU.All was well,but no start!The plug which went into the Electronic Ignition module was faulty.It was a weird type,but I found some bits which were similar & repaired it.---all OK.How come the car gurus didn't check that first up?If they had been working on an old style car ignition,that is probably the first place they would look,but it appears they were so suspicious of the "computer" that they locked into that as the source of the problem.From the time we bought it,the car had another "funny"---at cruising speeds,it would occasionally "hesitate",then continue as normal.The "gurus" again blamed the "computer",but couldn't find anything,so we lived with it.Eventually this morphed into a situation where the car would not just hesitate,but stop.(Luckily,the thing had failed in the driveway this time)As I was busy at work,we got the callout Motor Mechanic to have a look at it.He diagnosed it as "The computer" & replaced it with a spare.Of course,it did it again within an hour,so he refitted our ECU & effectively gave up.It looked enough like the original ignition fault to make me suspicious,so I checked the previously repaired plug--all OK!I Then dragged the poor old BWD out,& backprobed the ECU again.--allOK again!Googled--someone had experienced something similar with injector problems,so I pulled out the throttle body.One injector was incorrectly fitted.Why the fault got worse is beyond me,I just bought a good throttle body complete with injectors from the wrecker & all was well.

author: G7PSK
author_rank: Super Contributor
timestamp: March 17, 2013, 09:35:24 am
content: I had one of those PC scope adapters once, the main problem was that you could not put more than 5 volts onto the probes and there was absolutely no protection between the front end of the scope unit and the computers usb socket so a spike on the probe could blow up the computers usb.

author: saturation
author_rank: Super Contributor
timestamp: March 17, 2013, 02:19:03 pm
content: I second this, you can find reviews of the Velleman, UT81B, and other 'intermediate' DSOs between the Chinese full portable DSO, priced $<200 in the archives.I use a Velleman HPS40 which is the older version of the the 140, for looking at car waveforms but I am not a professional so use it sparingly, its all manual scope and for the cost in the USA ~ $200, delivered, it works. It went down as low as $130 in liquidation, at that price its very cost effective, but for daily use as a repair technician, it can be taxing because its ergonomics are so low. Most auto waveforms are under 100kHz, and require only the most basic triggering, if just auto triggering.The 81B is a better scope than the Velleman, but in the USA, its only available via mailorder from China.A lot depends on price, above $200, the Handheld Owon's are a better bet, but you must buy it locally because of quality control issues, the Velleman QA is better and so is honoring its warranty.Quote from: M0BSW on March 16, 2013, 09:08:07 am