The Trainer #72 - Mastering Your Digital Multimeter (DMM or DVOM)
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- Опубліковано 5 сер 2024
- What were the first tools you ever purchased? Of course, there was the selection of the basic hand tools and power tools, right? A basic tool box to keep it all in was also part of that initial investment, I’ll bet. But what about diagnostic equipment? Was a high end scan tool on your list? What about a scope? Odds are, neither were during the early part of your career.
I am willing to bet, though, that a Digital Multimeter was. It’s a tool that is as vital to a technician as a hammer is to a carpenter. We use it to measure the resistance of electrical components, voltage potential in a battery, and some of us even use it to measure current flow in a working circuit. Good uses, all, but there is so much more that the DMM can perform and so many ways it can be used to solve a variety of diagnostic dilemmas.
In this edition of The Trainer, we’ll take a look at the features included with most DMMs you may or may not be familiar with, how to perform some of the more standard tests with the meter, and then share some testing techniques you may never have considered using your meter for.
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Due to factors beyond the control of Motor Age, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. Motor Age magazine (UBM Americas - Automotive Group) assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. Motor Age recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of Motor Age, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not Motor Age magazine or its corporate parent, UBM Americas. - Авто та транспорт
Hey Pete, thanks again for the great info and content that you and the Motor Age team are always putting out! 👍🏼 I have been in the trade for 30+ years and have gotten a bit of a reputation in my area as an electrical diagnostics specialist, my customers say that, not me. However, even though most of us know everything you just spoke about, it never hurts to hear it again, and again, and.... you get the idea. Nobody is perfect or knows everything, and even if you do it doesn't hurt to refresh your memory or sometimes you may suddenly see something from a different perspective. We are never to old to learn! Cheers and respect to you and to all of the mechanics out there, professional or diy backyard let's stick together! 👌🏼👍🏼
It’s also important when checking parasitic electrical draw to make sure the hood switch is rigged to be in the closed position (taped down, or temporarily zip tied down, etc.), and all the doors are closed. Otherwise, with the hood up the electrical system won’t go into sleep mode. Also, after testing, be sure to remove the tape or zip tie from the hood switch. I put a Post-It note on the vehicle’s dash instrumentation as a reminder of anything that can easily be overlooked…..when working on cars, it’s easy to set distracted by interruptions, phone calls, customers, etc.
Thanks for those great comments!
I have got so much useful information from this program I have been a tech for 43years Pete you are the best for me to learn from I work on heave duty trucks been with the same dealership for 31years in Tuscaloosa Alabama
Glad you're enjoying it!
Hello Mr. Pete
Thank you for sharing with us all your knowledge and Wisdom...
I personally have learned a lot from you,
Im your No. 1 fan
See you next time
Very good information! Thank you so much for taking the time.
Great video Pete, thank you sharing. Measuring the voltage drop across the fuse to find a parasitic draw is a fantastic method for diagnosing the draw.
Good refresher Pete
Good job! Thank you for the info.
Great video, thanks for sharing..
Very informative. I'll get more use from my multimeter now.
Thank you for sharing, learned something new
I appreciate the information.
Been using Flukes for years in heavy industry (steelworks).Brilliant meters and virtually indestructible.
great video
Like the test for checking starting/charging, first time I've heard of that one. I'll try it on my 2018 Transit as I've been having some starting issues I don't think are normal but the local dealer told me it is. They wouldn't even take the time to check it out.
Long before the Automotive Electrical systems became so Advanced, FLUKE was the Industry Standard for Industrial Instrumentation. Before that it was a Simpson 260 DVOM. Pete, what did they use in the Navy? Thanks for So Many Great Video's!!
KNOWLEDGEABLE Sir Pete Meier Motor Age
Thanks 👍
From Nick Ayivor from London England UK 🇬🇧
The 9.51 minimum voltage you are showing is the cranking of the engine with the battery dropping to 9.51v before the engine starts correct? Then of course you have your charging voltage. Thank you Pete.
Ghost voltage is usually 60 hertz from your florescent lights. It shows up better on the scope.
To clarify what they mean by True RMS. True RMS, VRMS, ARMS and WRMS is
the RMS measure of both the AC + DC components, it's integration of the
area under the curve. This meter measures VACrms and AACrms, so it
separates the DC component. It should state TRUE AC RMS, but like most
meter manufacturers, they don't. There's a lot of misunderstanding on
this thanks to marketing in companies. Take a look at a Fluke 187 or 189
where they actually measure TRUE RMS, but on the meter they call it
AC+DC (in Blue). Most people are fine with this, since they typically
measure line voltage or clean DC (battery or SMPS supplied). However,
measure a DC source with high ripple current and you will not get a real
measure, such as in automotive battery chargers that use a linear
charger (large transformer based, not SMPS). Knowing the True RMS allows
you to properly design for things such as thermal, efficiency and
safety (fuses, breakers, thermal cutoffs, etc..) and to prevent over
charging or over powering a battery or device. Class 2 devices, as those
that fall under UL1310, have to comply to VRMS up to 2kHz for both
indoor and outdoor ratings. Landscape lighting, LV pool lighting, USB
3.x Power Port also must comply. The reason for this in LV applications
is because of the breakdown voltage of the skin. How to tell, if the AC
symbol on the display only has a tilde ~ it's ACrms. If it has both the
tilde ~ and a straight line - above it, its RMS. Some meters (Fluke 187,
189, 287 & 289) use the DC for both DC and RMS, so it will have
both if the second function feature is RMS. The Dashed straight line on
the flukes means it can also properly measure pulsed DC.
My friend got 8 volts on his fuel pump but when I hooked up my scope you could see the computer duty cycle and the correct voltage and ground.
Great info
Hey Pete, do you still do live videos?
also how do you do the voltage drop test with the fuses with the plastic caps on them?? i think there called j case fuses
If you mean the clear caps, you can remove them if need be. The fuse method for locating drains is only one method, and a pretty good one, that can be added to the other ways for testing for drain. Use the one best suited to your situation.
I’ve had my Fluke 77 for over 25 years, and I got it used…
I also have a fluke 88
Number one tip fluke says is
Always start a test from meter off position
That way you are more likely to set your meter to the correct position
Sample if your going to test for bad alternator diode after checking alternator voltage going from DC volts to meter off then AC volts or if your going to check current
Go to meter off then amps
This method is the fluke recommend system in their self pace module along with many other tips
One accessory i got with it is the self pace training module
It came with fluke 88 operation video
Then a test, a battery, diode, resistor, printed circuit board
After watching the video you take the test and mail it in
Along with my 88 I have inductive tach adapter
Fluke pressure vacuum transducer
Contact temperature thermal couple with air liquid contact tips
Inductive amp meter
$$$$ not a cheap tool
Get a few extra amp fuses for the amp circuit
Maybe consider camera angles as your large hands completely blocked the view of multimeter lead(s) placement on the tiny fuses for the novices out there. Otherwise outstanding presentation thank you very much.
Thanks for this great information. I just got my first Multimeter and realized I have a Cat III 600 volts, not 1000. I’m going to use mine at home on a 1989 Porsche 944 and a 2012 Prius, and around the house. Do I need to return / exchange my unit for 1000 v, or am I alright as long as I don’t use this for heavy duty vehicles?
The voltage rating is for High Voltage systems like you would encounter on a hybrid or electric vehicle. The leads, too, must be rated CAT III before trying to measure these systems - along with training in safety around them. If you're going to try and work on the HV components, I'd trade it in for the 1000 v model.
@@MotorAgeMagazine That's a fantastic response; thank you very much again for all the great training in these videos.
Triplett has high quality meters at a much better price. Ideal is good too. The Chinese are making meters with the same features. If you ever open your Fluke meter you will be surprised to find a small circuit board with very little on it. What you are looking for in a meter is the insulating quality of the case and leads. Is that insulation really CAT III? And is the the true RMS really true?
what about a test light to be the first electrical diag piece equiptment to grab
I use a test light in a later video, but primarily to show how it can lead some down the wrong path. You can't test a loaded circuit with one or get a good feel for any unwanted resistance that may be present. Just my opinion....
If you get a low voltage switch to duty cycle or percent because a computer could be operating it and you might think it's a voltage drop
Sir may I know if we can used the current clamp to monitor the parasitic draw when looking for a circuit that have a parasitic draw tnx Sir
Parasitic draws can be very small. You can use a low amp current clamp and your meter, but both tools have to be fairly good ones to be accurate.
@@MotorAgeMagazine Sir your reply much appreciated tnx
16:10 so that 10A fuse had a resistance of 7.4milli Ohm? Just making sure I'm understanding correct.
If that's the number you come up with when plugging it into Ohms Law! Me personally? I could care less - if there is voltage drop across the fuse, current is flowing. And if there isn't supposed to be current flowing, I know where to start looking for the draw...
@@MotorAgeMagazine I guess it doesn't hurt to understand a little more about the maths if you want (which I do), though I get the point about it not making a difference in the context of diagnosing what's drawing current when it shouldn't be.
Sir I wacth your presentation regarding parasitic draw in a circuit you put one lead of the meter to one end and the other lead to opposite lead and there's a voltage drop it's my assumption is correct tnx Sir
If you mean the demo I did in this video, yes - we are measuring the voltage drop across the fuse. No voltage drop - No current flow is occurring. If a voltage drop is measured when the circuit(s) are supposed to be off - that's where the problem is.
@@MotorAgeMagazine Tnx for reply Sir
👍
i built my first meter as aheath kit in mail order basic elec course an analog that i used for years a meter will not lie (you can trust it ) that was back in 1965 ihavseveral digital meters now but i still use the analog when testing condensers the needle is better
Have you seen a particular alternator develop a load within so that with ignition off(maybe ign. on I can't remember,engine was off) you get a reading from case to battery ground maybe as hi as 85 to 90 % of supply voltage
Thanks Pete. Debating on the 88v or 87v.
White Tiger
I think the 87V is true RMS, the 88V is not.
707SonomaComa I just got the 87V for just that reason
And for 4 years before that I had a Fluke 115 True RMS
I find it kind of interesting you never mention what everyone should know you never mention the voltage is DC
Auto ranging meters are not good for hands on beginners
Abdoulie Jallow, why not?
i think is complicated and difficult to learn not sure too.
it makes things easier and it does many things for you insted u doing things fot your self.
flukes prices are totally ridiculours and total bs, nothing but a greedy company, that's all they are.
Show the meter. Too much lecturing
Fluke is also woke
EV is a fad. It will fail like it did 100 years ago.
5 min. Video drug out to 18 min. I recommend watch at 2 times speed.