Volt drop testing using scopes

Ask for and share advice on using the PicoScope kit to fix vehicles here.

Re: Volt drop testing using scopes

Postby AuthorMike » Mon Nov 14, 2016 9:55 am

Cleaned - Any problems please feel free to message me.

Keep it informative please chaps.
Mike Valentine
Technical Author @ Pico Technology UK
AuthorMike
Pico Staff Member
Pico Staff Member
 
Posts: 302
Joined: Mon Jan 31, 2011 11:22 am
Location: UK

Re: Volt drop testing using scopes

Postby andrewbishop66 » Mon Nov 14, 2016 1:41 pm

Hi Tech
best way to do ohms law now is with an online cal or a wiggit on your phone the double it only works with a certain set of figures


Thanks andrew
andrewbishop66
Advanced User
Advanced User
 
Posts: 66
Joined: Wed Jan 20, 2016 10:16 pm

Re: Volt drop testing using scopes

Postby Technician » Mon Nov 14, 2016 10:35 pm

Thanks Andrew,

I only ever came across the idea because it was an examination question, multiple choice.
Technician
Advanced User
Advanced User
 
Posts: 71
Joined: Thu Apr 24, 2014 8:32 pm

Re: Volt drop testing using scopes

Postby STC » Mon Nov 14, 2016 11:54 pm

In an ideal world Halving and Doubling may work, I trust it does.

However in the real world we don't get easy even numbers to work with. Hence it would be foolish to lose sight of the basic formulae and more foolish not to rely on it.

I use rule of thumb for simple numbers but an APP on my phone for Speed, Ease and Accuracy.
User avatar
STC
Zen Master
Zen Master
 
Posts: 369
Joined: Sun Sep 13, 2015 2:10 am

Re: Volt drop testing using scopes

Postby Dave Hill » Wed Nov 16, 2016 7:29 pm

It is a little difficult to understand quite how this thread has unfolded, as there appears to be a degree of "tidying up" done by admin.

I don't wish to discredit the status of a Master Tech, but I can quite easily believe that a certified MT might hold the opinion about the limitations of volt drop testing, in preference of resistance testing alone. For me this is complete nonsense & I would challenge anyone who tries to suggest that testing for resistance alone, is an adequate way of assessing circuit functionality. Resistance really is futile in this instance.

I have an Ex Peugeot Master Tech working for me at the moment. His MT status was still current until very recently & I still have to remind him to check wiring properly. :shock:

For me though, a thorough understanding of volt drop testing & why it is important, forms the cornerstone of a good auto electricians knowledge base. I would be very interested to know, just how many workshops around the various world regions, have someone on board who knows about it. Certainly in my experience, when ever I ask the question, I tend to see a lot of blank looks & vacant expressions.

It is quite a concern I think, when we consider that the most basic & probably the most common task that any workshop is faced with, is the diagnosis of a humble starter motor. A component that has not really changed a great deal for many years (an amazing fact when you consider the advances in all other areas). The process of accurately diagnosing a starter motor failure is heavily reliant on volt drop testing & the lack of understanding of how to effectively perform these tests is shocking! I understand that there is a widely held belief that this is really only the domain of the auto electrician, but in reality most mechanics will condemn a starter motor (sometimes successfully) based on other, less reliable & often very crude test methods. Volt drop testing is so simple, that there really is no excuse for anyone who claims the right to lift the bonnet & get stuck in, who says that they don't understand it.

Image
Dave Hill
Advanced User
Advanced User
 
Posts: 52
Joined: Fri Jun 22, 2007 8:15 am

Re: Volt drop testing using scopes

Postby STC » Wed Nov 16, 2016 8:31 pm

I don't wish to discredit the status of a Master Tech, but I can quite easily believe that a certified MT might hold the opinion about the limitations of volt drop testing, in preference of resistance testing alone. For me this is complete nonsense & I would challenge anyone who tries to suggest that testing for resistance alone, is an adequate way of assessing circuit functionality. Resistance really is futile in this instance.


Halleluiah :D :D

There was some Hoo Haa about cars built pre or post 2005 being suitable / not suitable to Volt Drop testing :?: :?:. Then it got messy :D

Dave
Only thing that I will add, and this is my very own personal "hands on" experience in the UK, is that every Assessment that I have been involved in as candidate are BIG on Volt Drop Measured in Millivolts. That goes for the Practical & Theory elements of each assessment.

My weapon of choice is always the scope (whether it be my Fluke Handheld or the Pico) and an assortment of bulbs for VD

I also subscribe to the theory that the Digital Voltmeter has No place in the modern automotive workshop other than to measure 60 ohms across a Hi Speed CAN network - Period !!! On that I stand to be corrected.

This normally attracts some criticism from the purists not in favour of "unconventional tools" but I do put my Power Probe 3 to very regular use, great for initial assessment as long as you have a thorough understanding of the circuit under test.
User avatar
STC
Zen Master
Zen Master
 
Posts: 369
Joined: Sun Sep 13, 2015 2:10 am

Re: Volt drop testing using scopes

Postby Technician » Thu Nov 17, 2016 12:55 pm

It may surprise you Dave that in most garages with targets that in my experience "Dealerships" and "Small Garages" that grabbing the scanner and reading fault codes to use as a diagnostic is the norm, even Snap On with their many CPD courses I have attended have said the same, "Fault Codes" are not the cause of the fault, "My words". Outside of a college training course I have never seen anyone do a volt drop test under a bonnet or anywhere on a vehicle for that matter in my whole life, its a world of plug and play. I'm not saying it is right, I agree it is wrong, but until the government actually do something about it, like stop people working on vehicles with a license as STC said, nothing will change, except some people will die when working on Hybrids, yes STC I have completed training courses on Hybrids, just for my own piece of mind. The license was first introduced back in 1983 as I vaguely remember, but there are too many other stumbling blocks in the way preventing it happening, the IMI as I speak are trying to get it in for electrical vehicles, time will tell how it goes.

While I have no intention of undermining Master Tech's I would like to point out that to become one a person requires about five years experience before that person can go on a competency based assessment, and if the Master Tech has worked in a good organisation like a dealership with customer relations experience then that will help as well, however I would like to point out that the aTa system has not been here forever, and in so saying this there are many mechanics, auto electricians since time began not got that aTa Certification because it was not available to them before it was thought up, and this does not mean that it is the bees knees, in that everyone should run out and get it, some people in the trade with years of training will have science degrees, Masters, PhD's etc, should they all run out and get a Master Tech Level iv qualification/certification to prove their competent? As a government official once said to me some 25 years ago, somebody has to write the book/material for the rest to follow the instructions.
Technician
Advanced User
Advanced User
 
Posts: 71
Joined: Thu Apr 24, 2014 8:32 pm

Re: Volt drop testing using scopes

Postby AuthorMike » Fri Nov 18, 2016 9:38 am

Hi,

This morning I have again cleaned this thread.

I urge all forum members to take note of my new thread (topic15451.html). Please also note that cleaning of the forum is only completed when an Admin member feels that there is no benefit coming from the posts, or that the behavior of members is detrimental to the forum.

If you have any problems, please, feel free to email or PM me directly. Links to both can be found to the right ->

Regards,

Mike
Mike Valentine
Technical Author @ Pico Technology UK
AuthorMike
Pico Staff Member
Pico Staff Member
 
Posts: 302
Joined: Mon Jan 31, 2011 11:22 am
Location: UK

Re: Volt drop testing using scopes

Postby Dave Hill » Sat Nov 26, 2016 12:11 am

Technician wrote:It may surprise you Dave that in most garages with targets that in my experience "Dealerships" and "Small Garages" that grabbing the scanner and reading fault codes to use as a diagnostic is the norm, even Snap On with their many CPD courses I have attended have said the same,



Huh?

Sorry Tech, that does not compute. :?
Dave Hill
Advanced User
Advanced User
 
Posts: 52
Joined: Fri Jun 22, 2007 8:15 am

Re: Volt drop testing using scopes

Postby STC » Sat Nov 26, 2016 1:42 am

Dave Hill wrote:Sorry Tech, that does not compute. :?


Hi Dave, Now I wondered that too, on many levels.

First, Snap On do not offer any CPD (Continuous Personal Development ???)

One wonders what that would be a Continuation of ???

What they do offer is Product Training Courses & a handful of evening seminars covering the very basics for which you get a Certificate of Attendance, and just that: Attendance!!! These Seminars, which I have attended, are more aimed at sliding their Diagnostic Machines and updates off the shelf. Good Marketing but never valid or worthwhile CPD.

More a "Fred in a Shed" quarterly gathering.

Outside of a college training course I have never seen anyone do a volt drop test under a bonnet or anywhere on a vehicle for that matter in my whole life,

How are we to take that? Will "Tech" now come along and back track then add "Except for him and his Garage" to this thread ?

For all the good educated technicians that I know, VD with a Scope and Correct Load testing of Actuator Powers and grounds (pre & post 2005) is second nature, Safe & Conclusive.

This level of unconscious incompetence and ignorance is just not funny or acceptable and an undeserved stain on the reputation of this trade.
User avatar
STC
Zen Master
Zen Master
 
Posts: 369
Joined: Sun Sep 13, 2015 2:10 am

PreviousNext

Return to Diagnostic discussion

Who is online

Users browsing this forum: No registered users and 1 guest