Oscilloscopes for automotive diagnostics?

Discussion in 'General Electronics Chat' started by Chris Wilson, Dec 2, 2011.

  1. Chris Wilson

    Thread Starter New Member

    Dec 2, 2011
    7
    1
    I have been using a USB scope but realise just how little I know about scopes and feel the need to back track and get some basic general info before committing to a potentially costly purchase of a bench type scope. I hope someone can find a few minutes to guide me here, please?

    I am currently using a Dataman USB scope http://www.dataman.com/oscilloscopes/da ... scope.html for basic automotive diagnostic work, looking at injector and coil waveforms, reading the outputs of cam and crank sensors, both Hall effect and magnetic, watching thermistor voltage outputs, and looking at throttle position sensor outputs, etcetera. It is not an automotive specific device like, for example, some of the Picoscopes, but this has perhaps worked to my advantage, as rather than pushing on screen menu buttons to set up scaling automatically, I have had to think about what I am trying to measure and do it manually. It has helped me get a basic grasp of signal levels.

    I now find carrying a laptop around and the Dataman scope, making sure the battery in the laptop doesn't go flat, being worried something's going to get knocked on the floor, blah blah, is a PITA and would also like a bench oscilloscope. Ideally I was thinking about those with battery power options, but I feel these will be out of my price range and I will have to continue to use a USB scope and the laptop when on the road, or inside a moving vehicle.

    I now find myself realizing just how poor my grasp of scopes in general is. I need advice on whether I should be looking at analogue or digital bench scopes, what bandwidth I need to look for, and how many channels I really need. I certainly need two, but I have a Thurlby Thandar 20 MHz multiplexer http://www.radiomuseum.org/r/thurlby_os ... lexer.html that might allow me view multiple injector or coil patterns on a single scope input. I have never tried it as I am told you need a scope with a degree of persistence to use it, and I don't think a USB scope would have this? I would also like a colour scope, to make differentiating two or more traces easier, and I also like the USB scope for its ability to show voltage levels and things digitally on screen. I suspect, but don't know, that these criteria will mean I need to look at a digital scope?

    The other thing I need advice on is depth of memory. I know Pico go on about how important this is for storing enough data to find an intermittent glitch. It's not something I have used with my Dataman USB scope, but i can see how it would be useful for finding more obtuse issues.

    Size and age of machine isn't a real issue now I have decided to consider a bench based instrument. My budget is £600 UK max, which is about $950 US, so will probably be looking at used stuff. I quite like vintage stuff, so am not necessarily looking for anything on the basis of it "looking modern". I would not want something totally irreparable unless it was dirt cheap though. Can anyone give me some pointers please? I have looked at some of the Far East handhelds, but not sure if they seem too good to be true and I might be buying junk?

    Thanks for reading.
     
    Last edited: Dec 2, 2011
  2. ssutton

    New Member

    Sep 12, 2011
    16
    0
    Hi Chris,
    ASE master tech here with lots of time on a scope in auto apps. In general, a 20 mhz digital scope should cover most of your needs. This is about as basic as it gets. I use a fluke 123 scopemeter. Also, there is optional software that allows you to log data on your PC if you have such a need. This type of scope will not cover every possible scenario that you will come across, but in general 99% of normal stuff should be fine. I have an analog scope as well, but use it rarely, the digital scopes are so much more useful.

    Scott
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Gee, two people with Thurlby Thandar items in so many months... is your Thurlby Thandar a DSA524 Storage Adaptor that can save data files?

    [eta]
    Oops, no - yours is a different model. Well, if you run across someone who DOES have a DSA524 adaptor, would you let them know about this?
    [/eta]

    If so, I wrote a program in C that you can use to convert the binary data to MS Excel .csv format for import.

    See this thread:
    http://forum.allaboutcircuits.com/showthread.php?t=60966

    Sample scope image:
    [​IMG]

    Sample image from converted data:
    [​IMG]

    Reading through the entire thread will help you to understand the hows and whys of it.

    Anyway, if you can find a Tektronix 'scope over that side of the pond, they are quite durable. Replacement of the electrolytic caps is suggested if the scope is rather old; that will extend the life of it significantly.
     
    Last edited: Dec 2, 2011
  4. Chris Wilson

    Thread Starter New Member

    Dec 2, 2011
    7
    1
    Thanks Scott, I actually have access to the Fluke, a friend has one,, I was looking more for a full size bench machine with as large a display as possible. A lot of my work is on race engines with programmable aftermarket ECU's like Motec, and although they self diah=gnose to a point, I am often chasing sensor issues and wiring faults as some are fitted by hobbyists in a rather haphazard manner. I would like something that sat on the bench and was a permanent fixture in the shop. What about these beasties? A friend has got one he would let go of cheaply.

    http://www.testequipmentconnection.com/specs/HP_54501A .PDF

    Thanks again Scott.
     
  5. Mickster

    Member

    Jan 10, 2010
    25
    11
    You have to consider the environment within which you are carrying out your tests.

    There's no substitute for a road-test, replicating the driving conditions during which the customer has observed a particular fault.

    You can have the fastest scope on the market, but unless the conditions are met which create the fault, all you are going to see is a perfect signal unless something is obviously breaking down.

    Some frown upon USB PC scopes and deem them to be a toy, but they definitely have their place for us. I have the 4ch 3000 Picoscope Automotive kit and have been quite happy with it. It doesn't have the same sampling rate as high-end electronics diagnostic equipment which is designed to deal with high Mhz or Ghz signals, but for the relatively slow environment which comprises automotive use, it is quite proficient.

    I'd rather back-probe a couple of suspected circuits with the Pico, set off on a roadtest with the laptop, hit 'spacebar' when a fault occurs and review data in the workshop, than try to do the same with a bench-unit. At the least, you will need a 12V to your-countries-AC-Supply inverter, just to power a bench scope, then some miraculous fingerwork to trigger during a fault.

    The PicoScope series of automotive scopes can save the last 32 frames of data, from the point of trigger, for replay at a later date. Depending upon the timebase selected, you can zoom pretty far in on your captures and detect signal drop-outs which would not normally be observed by other means, such as data-list captures with scan-tools, meters, etc.

    For more info regarding automotive scopes, you might wish to visit Autonerdz:
    http://www.autonerdz.com/cgi/yabb2/YaBB.pl

    N.B. I have no connection or affiliation with Picoscope, or Autonerdz, I simply wish to pass on information which may be of help to the OP.
     
  6. Chris Wilson

    Thread Starter New Member

    Dec 2, 2011
    7
    1
    Ho SgtWookie, I only got the TT unit today, it's merely a multiplexer to allow several inputs to display on a single output that feeds a separate scope. I am hoping it may allow me to see say 4 or six injector signals at once, in a parade, with the right imaginative triggering means. I know little of electronics, but am trying to drag myself, at a late stage and age, into the digital world ;) I am having to because even an amateur level race car is now choc a bloc with electronic gizmos, even CAN BUS stuff :(
    I don't have any documentation on stuff on my TT multiplexer, it came "as is". I like TT stuff, we see loads of it here in the UK as it's British made, people here rate it quite highly for simplicity and reliability.
     
  7. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    When you say the Fluke, are you talking about a scopemeter?
    Because when most people refer to "a fluke", they are talking about a digital multimeter. A scopemeter is not a digital multimeter; it is an oscilloscope. An awesome oscilloscope. It has a screen as big or bigger than any benchtop o-scope I have seen. I use a fluke 192B scopemeter and it rocks. pricey, but you get what you pay for, especially when you're talking about a brand like fluke, known for durability, accuracy, and all around goodness.
     
  8. Chris Wilson

    Thread Starter New Member

    Dec 2, 2011
    7
    1
    Yes, I am taliking about a hand held oscilloscope cum multimeter, DB meter etecetera. I think my pal has a 192, I know he's on about getting the colour version next year. Most of my work is on race cars, so I can't road test them, 99% of diagnosis is in the shop, or occasionally on a dyno. Maybe I should just get a better lap top and stick with the Dataman USB scope, it's quite a decent spec. How much difference would running it on a laptop with USB2 rather than USB1 ports? Don't laugh, the shop laptop is a "bit old" ;)
     
    strantor likes this.
  9. MrChips

    Moderator

    Oct 2, 2009
    12,415
    3,354
    For a 4-channel color digital bench top you are looking at a lot of £.

    I was going to suggest sticking with your USB scope. You can buy a new netbook for under £200 these days and this gives you lots of portability. Later you can upgrade to a better USB scope. The prices will come down.
     
  10. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Whilst scopes are handy for seeing the output of sensors and all the modern control gubbins, be very aware that there are some pretty high voltages knocking about around IC engines.

    Traditional engine oscilloscopes were specially hardened to cope with this, modern electronics is less forgiving.

    go well
     
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