DSO for Automotive work - Page 1
Forum section: electronics / testgear

author: Zeecue
author_rank: Contributor
timestamp: January 05, 2016, 03:57:31 pm
content: HiI have looked a numerous reviews and tests of different entry level scopes, but I still can't decide what to get.I quite like the portability of the owon, but dragging a power cable with me is not that big of a problem.It might be used for FlexRay measurements, but how fast a scope would I need for this ?I can also see that many people dislike the owon because of bad software, but is this still a problem with brand new ones too ?

author: R_G_B_
author_rank: Frequent Contributor
timestamp: January 05, 2016, 04:22:43 pm
content: People in the automotive say get a PICO scope.If you can? get an old snap on vantage it can do things an oscilloscope can not. Its a power graphing multi meter. That can graph volts, ohms, RPM, frequency, duty cycle, pulse width, in graphical form from 1 second to 16 hours. You do not need an oscilloscope with a long record length when using with one of these. Its a handy tool for electro mechanical testing.Some examples below:http://tractortech.com/waveforms/waveform.htmlhttp://www.realmeangarage.com/technonerd/20030714DL.htmlR_G_B

author: free_electron
author_rank: Super Contributor
timestamp: January 05, 2016, 04:35:18 pm
content: flexray ? you better get a machine that has a protocol decoder for that ...

author: Zeecue
author_rank: Contributor
timestamp: January 05, 2016, 04:40:09 pm
content: Thanks for the quick answer, already got a USB connected DMM that lets me do all that, and graph it nicely on the PC, but its not often its needed, mostly for faulty temperature sensors and such, that can show a "dip" in resistance at a certain temperature.And I'm not sure if the SnapOn can do canbus/FlexRay.The picoscope is nice, but expensive and is used with a PC, which we all know breaks down when you need it the most. (Atleast that's what happens alot on my diagnostic PC at work) and the original diagnostic DSO is having a hard time to even trigger on a canbus signal, and changes from 2V/d to 0.5V/d, so either the signals are small and hard to see or goes outside the window.

author: Zeecue
author_rank: Contributor
timestamp: January 05, 2016, 04:42:49 pm
content: Quote from: free_electron on January 05, 2016, 04:35:18 pmWon't need to decode the bus, its all nicely implemented inside the control units regarding faults. But what the units can't see is fx a canbus that have the voltages a bit wrong due to fx a short, or to check if its one or another control unit that won't "talk" on the bus.

author: tautech
author_rank: Super Contributor
timestamp: January 05, 2016, 09:04:26 pm
content: Quote from: Zeecue on January 05, 2016, 04:42:49 pmIf you don't need decoding pretty much any of the cheap DSO's will do what you need, I think robustness, reliability, BW, physical size, weight, padded carry bag and local support availability should guide you in selection.Most have quite low power requirements and can be run from any cheap compact 12V inverter but that adds further cost but no power lead or outlet required.Then there's the various handhelds available, most have inbuilt DMM's that could be convenient for you.From the Siglent range:http://www.siglenteu.com/pdxx.aspx?id=94&T=2&tid=2I'd be confident the SHS806 will meet your requirements.

author: b.c.henry
author_rank: Newbie
timestamp: January 06, 2016, 04:46:29 am
content: I'm not sure if the original vantage is fast enough for CAN but the Vantage Pro is but then you're getting up past Pico prices. I use both a V Pro and Pico regularly and they are top notch. OTC (also rebranded under Mac, Matco, and Cornwell etc.) has some offerings as well. Handheld there is the 3840f which is plenty for automotive and laptop has the 3857, which has better specs yet. I have yet to use the 3040f or any of its variants but the 3857 works well once you get past the software glitches. Customer support is lacking with OTC but if you have a decent grasp of electronics it shouldn't be an issue. Both the V Pro and the OTC products give sample waveforms and vehicle specific hook up info (the Snap-On has a much more complete database). AES Wave also sells a single chanel scope branded as the uScope. It's a DSO Nano but with their own software loaded. It's a fun little scope and very affordable and user friendly. AES support is second to none as well. I cannot speak highly enough of the guys. You don't need to worry when ordering from them, they won't sell you a bad product. Anyhow, that's my 2¢.

author: electrolust
author_rank: Unknown
timestamp: January 06, 2016, 08:05:19 am
content: Quote from: Zeecue on January 05, 2016, 03:57:31 pm200Mhz

author: HighVoltage
author_rank: Super Contributor
timestamp: January 06, 2016, 08:27:32 am
content: Take a look at the older tektronix THS720P and similar scopesThey are great for automotive use and portableBecause of the old batteries being dead, these scopes can be picked up very cheaply these days

author: ADT123
author_rank: Regular Contributor
timestamp: January 06, 2016, 08:33:59 am
content: Quote from: electrolust on January 06, 2016, 08:05:19 amAutomotive FlexRay usually has a 10Mbps bus speed. You can think of this (from a scope capture point of view) as a 5 MHz square wave. For decoding and a reasonable view of the shape of the signal you want to capture at least the 5th harmonic so bandwidth should be 25MHz. Most scopes use sinx/x interpolation and need about 4x the sampling rate of the bandwidth so 25MHz bandwidth with 100MS/s sampling rate is OK for faultfinding automotive FlexRay.If you are however designing FlexRay systems where signal quality / integrity tests are more important then a significantly higher bandwidth / sampling rate makes sense & the 200MHz above sounds about right.

author: Zeecue
author_rank: Contributor
timestamp: January 07, 2016, 04:48:25 pm
content: Thanks for alle the good and really long answers.As I live in a old apartment without ground in the 230v plugs, would it be safe to measure 12v with the oscilloscope if I have a control unit home for internal repair/ look inside?

author: ADT123
author_rank: Regular Contributor
timestamp: January 08, 2016, 05:53:16 am
content: 12V will be fine without a mains earth. There are a few things to be careful about - one is that if the scope you are using has common (shared) ground between the channels as most benchtops do then make sure the grounds for each channel only go to vehicle ground or you can get a short.Another is be careful of ground loops if the vehicle is grounded via a scan tool, battery charger etc. Scopes with isolated or differential channels avoid this issue but that rules out the scopes in the list you have to vote on (actually it does not rule them out, just means you have to be careful). The Tek THS720P mentioned below I think is isolated. Many of the scopes designed / sold for automotive do not have common grounds (PicoScope 4425) or only have one ground shared between the channels (Snap-On), both avoid this issue.Although the car runs on 12V, inductive components have spikes when they switch that will exceed this. Injectors spike to over 100V and primary ignition on older vehicles to 300V. Make sure your scope can measure these voltages or use an external attenuator or divide by 10 scope probe when measuring these.

author: Zeecue
author_rank: Contributor
timestamp: January 08, 2016, 03:19:45 pm
content: Thanks, guess its gonna be a rigol or Owon then.The scantool wont be a problem as its either WiFi or Bluetooth connected on the cars I work on.I have always learnt to use the ground for the ground cable on the scope when measuring, and using a proper scope would be a bit more safe than the original scopemeter from VW/Audi, as it really easy to switch from voltage to current measurements, its a bottom in the software, just right next to the current probe button. Really stupid made. Do it and a fuse or control unit blows. As the scopemeter has a 10A thermal fuse, on the current mode.I noticed that the Rigol has a way better waveform update rate, than the Owon, but is this useful for anything ?