New to everything. Looking to buy my first oscilloscope - Page 1
Forum section: electronics / beginners

author: dieseltech82
author_rank: Contributor
timestamp: May 27, 2015, 02:24:59 am
content: I always hate doing this intro stuff but I understand the necessityAnyway, my name is Mike and I work for a John Deere dealership. A lot of what I do deals with the electrical portion of the machines, it seems I'm the go to guy for shorts, opens, CAN bus issues and so on and so forth. Just when I think I've seen it all, there stands before me a 4730 sprayer with a 6.8L Tier 3 emissions with Level 16 engine controller. I've seen and diagnosed almost everything this engine can do, or not do but this one has me and John Deere's technical assistance (DTAC) absolutely stumped. What's happening? The ECU is throwing a code for the cam position signal error and shows signs of either electrical interference or mechanical issues causing the erroneous reading of the cam sensor. I've tried everything and have come to the conclusion the only way I can diagnose this machine is with an oscilloscope. You see the computer actually detects there is noise on the signal wire but I cannot see anything but the output to my laptop, which resembles a seismograph reading of an 8.5 earthquake. I need to find out if it's electrical interference by identifying the intruding signal or if it's mechanical by observing the sine wave created by the sensor. Here are some things that I know:1) The signal for the cam sensor is rotating at half the speed of the crankshaft and the tone wheel has a special identifier on the tone wheel for TDC #1.2) The engine is a 6 cylinder, therefore there are 6 markers on the tone wheel and the engine max RPM is around 2300. With the camshaft rotating at half the speed of the crankshaft, it is 1150 RPM x 6 identifiers= 6900 pulses per minute, correct??3) The signal voltage input is either 5 VDC or 12 VDC. I should know this for sure but I can't remember off the top of my head.The sensor is a magnetic input type. It gets voltage supplied on one side and sends out a square wave signal on the other wire.What I would like to accomplish1) Observation of the sine wave while operating the machine.2) Isolating any noise I may find on either the a) signal wire or b) power supply wire to the sensor.3) Optional but would be nice to simultaneously observe the a) camshaft signal and input b) crankshaft signal and input.I know if I dropped 10k on an oscilloscope I could get the job done but I need to do this on a budget, a tight one. Honestly I may never use this thing ever again, then again once I learn how to use it, I may use it all the time. I'm drawn to the USB scopes on the market due to their compact design, interface with a computer and have an appealing cost to someone who is not intending to scratch the surface of the capabilities of the scope.Other considerations: I may be inclined to spend a bit more on a better one as my children show interest in electronics, such as robots and things of that sort. Heck, maybe I could actually repair a TV that has more than the capacitors blown out.Thanks in advance. I appreciate your time, knowledge and input into my decision on this new purchase. If this goes through, I will be seeing you in the oscilloscope forums!!!

author: Electro Fan
author_rank: Super Contributor
timestamp: May 27, 2015, 04:55:27 am
content: Roughly where are you located? What is the budget? Might be some ways for a vendor to give you a demo or maybe someone can help you out. Might also be possible to rent a scope for a month (they can be shipped). Might also be possible that for not much more than a couple or so month's rent you could purchase a scope that you could keep after this project. This doesn't sound like a problem that needs a 10k solution. We look forward to seeing you in the "oscilloscope forums." You sound like a nice guy that should have an oscilloscope. Check this one out in the meantime:http://www.tequipment.net/Rigol/DS1054Z/Digital-Oscilloscopes/

author: G7PSK
author_rank: Super Contributor
timestamp: May 27, 2015, 07:24:14 am
content: One thing to consider, the very cheap usb scopes have very low input voltages and no protection. Although the operating voltage of the engines systems is 12 or 24 volt (rare cases 48) there can be considerably higher spikes voltages present. For what a decent usb scope costs you can get a Rigol or the likes which will have the input protection.

author: ez24
author_rank: Super Contributor
timestamp: May 27, 2015, 08:02:27 am
content: Quotewhat does this mean? $100 or $1000big difference to memaybe a used Fluke scope that has a good resale value or a new one that also has good resale value, in case you change your mind and want to sell itand they make a special one for auto work

author: tautech
author_rank: Super Contributor
timestamp: May 27, 2015, 08:24:33 am
content: In my auto and engine experience most entry level scopes will display problemsIFyou know what you are looking for and know how to "drive" the scope.This implies some electronic knowledge is required.For modern equipment, just as you say there is also serial protocols to consider.Most auto stuff is VERY SLOW speed by comparison to consumer electronics and I be very surprised if a 100 MHz scope wouldn't do all you need. But it must be a DSO for the slow frequencies.To emphasise this point, divide 6900 by 60 seconds =115 Hz.I'd expect to meet all your 3 requirements with a 2 channel entry level scopeHave you swapped out the camshaft sensor?How old (Hours) is the JD?

author: dieseltech82
author_rank: Contributor
timestamp: May 27, 2015, 11:20:07 am
content: Thanks for all of the replies so far. The budget I'm looking at for this initial project would be less than 200, if possible. I was looking at this last night:http://www.amazon.com/Automotive-Diagnostic-Oscilloscope-Arbitrary-Counter4CH/dp/B00CPY8JX4/ref=sr_1_10?ie=UTF8&qid=1432724980&sr=8-10&keywords=hantek+usb+oscilloscopeThe review really caught my attention. The guy sounds just like me and seems very pleased with his use of the machine. I also looked at the Rigol and while a nice looking machine, I think the size benefit of the USB device would outweight any benefit to having a stand alone machine. The reason I say this is I have to carry this equipment up and down the stairs and fit it inside the cab with me. You'd be surprised how easily you can fill a cab up with test equipment and tools and then have to take them all out for a ride, a minimalist approach here is beneficial. As for location, South Texas is where I hang my hat at nightThanks again for the responses, keep them coming!

author: daybyter
author_rank: Frequent Contributor
timestamp: May 27, 2015, 11:27:18 am
content: http://www.amazon.com/Automotive-Diagnostic-Oscilloscope-Programmable-Generator/dp/B00BSR98KW

author: dieseltech82
author_rank: Contributor
timestamp: May 27, 2015, 12:58:21 pm
content: Quote from: daybyter on May 27, 2015, 11:27:18 amThank you for the reply. I always look at the negative feedback on Amazon before purchasing to help with realistic expectations of things that could go wrong. That being said, there seems to be a lot of issues with the software for the device. Has someone wrote new software/firmware for the device? Thanks.

author: dieseltech82
author_rank: Contributor
timestamp: May 27, 2015, 01:46:09 pm
content: Ok, the customer is getting a bit more restless now and so the shop is going to buy the scope. So my new budget is to get the scope cost as low as possible but it needs to be functional. I'm looking at something in the 500-600 price range. Again, the responses are all appreciated and I thank you in advance for your time.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: May 27, 2015, 03:48:10 pm
content: Heck, with that kind of money to throw around...Consider the Rigol DS1054Z. It's got a lot more capability than you need and it does have your actual needs covered (can capture slow waveforms, "roll" horizontal mode, recording and playback, setup storage, easily printable screenshots for documentation, mask pass-fail testing, etc.) It packs up into something about the size of a large ladies handbag. With your budget you could get the scope, the official Rigol carry bag, and still have some left over for longer cables, etc.There will be some learning curve if you haven't used a scope before, but this one is very easy to use. It has a few little quirks, nothing showstopping.No, I'm not a Rigol salesman!! I just got one a little over a month ago and I'm loving it.I hope you didn't get washed away by the floods over the weekend!

author: JackP
author_rank: Regular Contributor
timestamp: May 27, 2015, 03:51:44 pm
content: I believe the Rigol has a help feature (not sure though). If so, it allows you to see what the various buttons do (after pressing the help button).

author: miguelvp
author_rank: Super Contributor
timestamp: May 27, 2015, 05:01:47 pm
content: I love my Rigol, but I'm not sure how this piece of kit would fit in such a harsh environment as a garage.You should probably look on automotive forums, because even if a cheap scope would do, you have to consider what is it going to be exposed to, like grease, high temperatures (cold ones in winter) fluids, etc..So even if the DS1054Z fits your price range, if it doesn't survive how good is it going to be?I guess with a good cart that protects it and only taken out to the bay when needed might do the trick, but be aware that these types of scopes are not designed for that environment as far as I know.

author: rsjsouza
author_rank: Super Contributor
timestamp: May 27, 2015, 05:37:57 pm
content: Quote from: miguelvp on May 27, 2015, 05:01:47 pmPerhaps something like the ones below that can withstand some more punches? Unfortunately their price rivals the much more featured bench oscilloscopes...http://www.circuitspecialists.com/handheld-oscilloscope-dso1060.htmlhttp://www.tequipment.net/OWON/HDS2062M-N/Portable-Oscilloscopes/A "review" of the Hantek is in the link below:http://toolboom.com/en/Articles-and-Video/Review-of-Hantek-DSO1060-Handheld-Oscilloscope-Oscilloscope-plus-Multimeter.htmlUnfortunately I couldn't find much about its reliability or long term experiences with it.Three people at Amazon seem tolike the Hantek, while twelve seem tolike the Owon.

author: Howardlong
author_rank: Super Contributor
timestamp: May 27, 2015, 06:11:42 pm
content: Quote from: rsjsouza on May 27, 2015, 05:37:57 pmI have both of these scopes (well, the 100MHz version of the OWON [HDS3102-N] and the DSO1062 has been fettled to 200MHz anyway). I prefer the OWON solely due to the small form factor making it especially useful for very portable field use for quick diagnostics. However, note that when plugged into AC, the Owon is _not_ isolated when using the supplied PSU.I have some comparative notes herehttps://www.eevblog.com/forum/testgear/owon-hds3102m-n-handheld-scope-review-teardown/msg639550/#msg639550tagged onto the end of Mike's Owon review/teardown.

author: miguelvp
author_rank: Super Contributor
timestamp: May 27, 2015, 06:21:14 pm
content: That's a good point, there are probably requirements when you use a scope that is plugged into the mains.Specially if other equipment is connected to the vehicle.There are probably regulations on what equipment could be used and by who, but I know nothing about this.

author: rsjsouza
author_rank: Super Contributor
timestamp: May 27, 2015, 09:33:59 pm
content: Quote from: Howardlong on May 27, 2015, 06:11:42 pmGood info, Howardlong. <rant> C'mon, Owon! Is it really too hard to source a fully isolated switching PSU?!?We have these problems with our development kits as well... Some idio... ahem, luminary thought that a development kit that connects itself everywhere else via USB, Ethernet, serial, HDMI, etc. should be fully grounded all they way up to the hydroplant.</rant>

author: dieseltech82
author_rank: Contributor
timestamp: May 27, 2015, 09:55:19 pm
content: I went ahead and pulled the trigger on this:http://www.amazon.com/gp/product/B00CPY8JX4/ref=oh_aui_detailpage_o00_s01?ie=UTF8&psc=1If there is any additional information that you would recommend on how to use this scope, it would be appreciated. We shipped it next day, so I should be seeing it tomorrow. I also purchased BNC to Banana so I could use my fluke leads/backprobe kit to backprobe my connections while operating the machine in the conditions to replicate the fault. If I'm feeling froggy, I'll try and make a video of it and upload it to my YouTube channel. Thanks.

author: daybyter
author_rank: Frequent Contributor
timestamp: May 28, 2015, 03:03:48 am
content: Over in the hantek 6022be thread, there is a guy working on motocycles IIRC? Maybe you could share some experiences?https://www.eevblog.com/forum/testgear/hantek-6022be-20mhz-usb-dso/810/(Post 819)

author: dieseltech82
author_rank: Contributor
timestamp: May 28, 2015, 05:54:04 pm
content: Ok, the scope came in this morning and I think I have what I need to install the probes. From my research, the sensor is a permanent magnet type and will produce a AC sine wave. It looks like I need to install the two probes, one channel, on each side of the sensor to observe the signal. Any help with how to set up my scope to get a reading would be much appreciated. Thanks in advance for your time.

author: YLEKIOT
author_rank: Newbie
timestamp: May 28, 2015, 06:05:56 pm
content: Diesel Tech,I work right next to the John Deere plant that builds the Air Seeders here in Valley City, North Dakota. One of the line leads is in our local CERT effort. I can forward this to him if you like? We are talking the guys that actually make (and in some cases actually use, lots are farmers) the Air Seeders here, so their knowledge is fairly good!If you still can't figure this out after the scope is running, it might be worth a shot.Jeff

author: dieseltech82
author_rank: Contributor
timestamp: May 28, 2015, 11:02:41 pm
content: Quote from: YLEKIOT on May 28, 2015, 06:05:56 pmThank you for the offer. I've been working with JD DTAC on this case and I *think* I may have made some headway with the scope today.On a relate note to all you who have been following, I'm considering making some customer cables to make this more user friendly. Basically I need to make this process fool proof, if you know what I mean. Do you have any suggestions on where to source stuff like coax cable, BNC ends, BNC to Banana adapters? Also, I was looking at Digikey for BNC ends, they seem very pricey and I'm not really sure what specs I need to go with to make sure I'm getting the most bang for my buck and not wasting my money on features I don't need. I'm looking into making a wiring harness pigtail that will go inline with the crank/cam sensors and plug into the scope leads. I was thinking of going coax to within 6" of the sensor, adapter to banana jack and plug into my inline pigtail. This will provide less connections than I have now, should help with any signal integrity issues I may have running 10' of regular lead per side, so 20' overall and simplify the process for others. Thanks.

author: tautech
author_rank: Super Contributor
timestamp: May 28, 2015, 11:06:22 pm
content: Pomona is generally accepted as the best source of quality products:http://www.pomonaelectronics.com/

author: dieseltech82
author_rank: Contributor
timestamp: May 28, 2015, 11:41:55 pm
content: Does anyone on here make custom cables? This would save me from buying the tools. I may inquire to Pomona on the custom cables. I'm looking at 12-15 foot. Thanks.