Using A Multimeter

[Lakester]

hello,

i read where a multi-meter is an important testing tool for use on a boat. both electrics and engine's electronics can test a variety of electrical items. So i went and got me one. a good one with an infra-red no touch temp sensor, volt meter, continuity, etc.

now i know i can put it on V and read my bat voltage. i can put it to continuity and check a wire from one end to the other, such as a bat cable or a starter solenoid connecting wire.

but how else have u usued your multimeter to help u solve electrical related issues? how do u use it to check components, etc. what sort of actual problems did the multimeter help u to solve?

i hope this will be a good thread with lots of inputs and ideas!

regards
lakester

 

[jay_merrill]

Re: Using A Multimeter

I just did an ohms check on my charge coils and sensor coils. Charge coils were right at 900 ohms. where they are supposed to be. Sensor coils meaured at infinity on the grounding test, like they should but one read 12 ohms on the check using the common wire along with each, individual sensor wire. It is supposed to be 8.5 ohms, plus or minus 1 ohm.

BTW, you can do that test on your Erude too.

 

[Lakester]

Re: Using A Multimeter

hello,

ok, is there a post on how to do it?

regards.
lakester

 

[ThumbPkr]

Re: Using A Multimeter

With all due respect it would be very helpful to you to take a little time and study some basic electrical/electronic theory and you could answer these questions for yourself.That sounds like a nice meter that you bought and you stand a very good chance of toasting it if you connect it wrong in the circuit/range by mistake.
The newer digital autoranging overload protected meters of today are pretty forgiving of abuse but the older analog meters were not and you pretty much had to create good habits or you would burn them up or damage the meter movement beyond repair.
We have all (us old guys) trashed a meter or two in the past and I always encourage people to hang them on the wall over their workbench to remind them of what can happen when you are not careful or paying attention.
The more expensive the meter the better the lesson it provides)Ron G

 

[achris]

Re: Using A Multimeter

Being an electronics tech losing my DMM would be like having my arm cut off...

A couple of very useful tests you can do when troubleshooting engines are the following:

1. A 'volts drop' test. One area of continuous problems is dirty terminals. Particularly battery terminals. An ohms check will not show a connection that is only resistive under high load (current). Typically these are connections to battery terminals, connections on starter motors and solenoids. To test for unacceptable drop, put the multimeter on a small voltage range, typically the 2 volts range. Put one lead of the meter on the terminal and the other lead on the cable. You are measuring across the actual junction between the two. The meter should read very low, very close to zero. Now activate the high current device, like the starter motor, you should see a small increase in the voltage reading, but only very small. A reading of 0.1 volts is unacceptable and means the terminal needs cleaning.

2. The other function you'll find useful is the diode test. This is, surprisingly enough, for testing diodes. Test each leg of a bridge rectifier with this. Remove all the leads on the rectifier. Set the meter to diode test (-|>-) and put the red test lead to the + terminal (or red wire of a rectifier with wires not terminals) on the rectifier. With the black test lead touch each of the ~ terminals/yellow wires. You should get 'OL' on the meter, meaning open circuit. Now put the red test lead on the - terminal/black wire (or the metal body of a rectifier with only 3 terminals/leads) and touch the black test lead to each of the ~/yellow wires. You should see a reading of about 0.7 volts. This is the voltage drop across a diode that is 'forward biased'. Now put the black test lead on the + terminal/red wire and touch each ~/yellow wire with the red test lead. You should see 0.7volts on each. Black lead to the - terminal/black wire/rectifier body and touch each of the ~ terminals/yellow leads and you should see 'OL' (this means 'Overload' or more than the meter can read, you won't damage the meter, in diode test this means open circuit). If any of these readings are out or any reading is 0 volts, then the rectifier has GTG (gone to god)

One of the most useful equations in electrics is V=IxR, Voltage equals current times resistance. Rearrange it to fit what you have, like I=V/R if you want to know the current or R=V/I if you want to know the resistance.

The other equation is P=IxV. Power (in watts) equals current times voltage. Mix the two equations together and you have the most powerful maths in electrics. It's all I've ever bothered to remember in more than 30 years working with electrics.

Let's say you have a light you want to put in. The light is a 12 volt, 50 watt unit. What size cable should you use? For that you need to know the current drawn by the light. Easy... remember P=IxV, can also be I=P/V... current=50/12 (amps), or 4.16 amps. Find a cable that can carry 5 amps and you're giggling. It also means that the light has a resistance of... let's see if you can work that out.

Cheers,

Have fun with the multimeter ('probing' the dog is NOT funny!!! or legal in some states),

Chris.............

 

[Silvertip]

Re: Using A Multimeter

Fuel gauge senders as well as engine temp and oil pressure senders are essentially variable resistors whose resistance changes therefore causing the gauge to display the current condition. Diagnosing irratic or non-functional gauges would require use of a multi-meter (Ohms setting) to check the operation of these senders and sensors. As was pointed out, touching the probes to a powered circuit when you have the meter set to Ohms may very well toast it or at least pop an internal fuse. You cannot check a circuit using the Ohms scale on a powered circuit. For resistance tests the meter uses an internal battery for its power source. There are also some electonics principles you need to understand when you get into that level of troubleshooting. Parallel and series resistance is just one.

 

[Lakester]

Re: Using A Multimeter

With all due respect it would be very helpful to you to take a little time and study some basic electrical/electronic theory and you could answer these questions for yourself.That sounds like a nice meter that you bought and you stand a very good chance of toasting it if you connect it wrong in the circuit/range by mistake.
The newer digital autoranging overload protected meters of today are pretty forgiving of abuse but the older analog meters were not and you pretty much had to create good habits or you would burn them up or damage the meter movement beyond repair.
We have all (us old guys) trashed a meter or two in the past and I always encourage people to hang them on the wall over their workbench to remind them of what can happen when you are not careful or paying attention.
The more expensive the meter the better the lesson it provides)Ron G

hello thumb,

yes, good points. thanks. i am aware of electronic and electrical procedures. i posted the thread just to try to get examples of what others were doing and how they were using, their mm's, etc. from general comments, to specifics if someone wanted to share is what i had in mind. like achris and stip's posts...

regards,

lakester

 

[HyperFox]

Re: Using A Multimeter

Well I use my good old Fluke (funny name for a multi meter, eh?)

I used it a lot this fall when redoing the wiring on the boat by checking for resistance across wires.. A lot of wiring later, and now the lights work properly on the boat..

Im going to be using it more when it comes time to do some new trailer lights.

 

[Lakester]

Re: Using A Multimeter

Well I use my good old Fluke (funny name for a multi meter, eh?)

I used it a lot this fall when redoing the wiring on the boat by checking for resistance across wires.. A lot of wiring later, and now the lights work properly on the boat..

Im going to be using it more when it comes time to do some new trailer lights.

hello h'fox...

while studying mms online i read where if the resistance is high, continuity is low and if resistance is low, continuity is high.

so when u check ur wire's resistance r u looking for a specific value, or are u looking for low resistance to ensure hight continuity? do u also run a continuity ck as well?

regards,

lakester

 

[achris]

Re: Using A Multimeter

Well I use my good old Fluke (funny name for a multi meter, eh?)

Mine's a Fluke 73...

o when u check ur wire's resistance r u looking for a specific value, or are u looking for low resistance to ensure hight continuity? do u also run a continuity ck as well?

A resistance check is a continuity check. If you have infinite resistance you have no continuity. If you have no resistance you have continuity. You can have a high resistance, but not infinite, and still have continuity.

Chris.............

 

[achris]

Re: Using A Multimeter

Maybe you're thinking of an isolation test. When I work with 3,000 volts I use a 'megger' to check the integrity of the wires insulation, and this also shows us if there's water intrusion in the cable bundle. We set the meter to put 5,000 volts and probe the wire in question. We connect the other test lead to one of the other wires in the bundle and if there is any less than 50 million ohms between any wire and any other wire, we bin the cable, simple! We tend not to muck around with 3,000 volts and seawater!!!

Cheers,

Chris.............

 

[Laddies]

Re: Using A Multimeter

If your meter has a DAV or a Direct reading meter in it you can go to the CDI electronics site and get test procedures for your engine or post what type engine you have and get them here.

 

[jtexas]

Re: Using A Multimeter

Diagnose a no-start condition as solenoid/starter/wiring harness/keyswitch.
Trace trailer wiring faults.
Testing toggle switches.
Testing trolling motor power outlet.

 

[Don S]

Re: Using A Multimeter

Without a multimeter, finding a problem with anything electrical will be impossible. Short of throwing new parts at it till you find the right part. And if the problem is a broken wire, you will never find it without a meter. Unless you follow each and every wire.

Once you know how to use one, knowing when and why is easy.

http://www.google.com/search?q=Usin...d=ie7&rls=com.microsoft:en-US&ie=utf8&oe=utf8

 

[HighTrim]

Re: Using A Multimeter

Just another point to add, alot of different meters show different readings for zero, infinite, open circuit, etc... You have to know what your meters display will show for that reading or else your test will be pointless.


Lakester, you may also want to invest in a DVA meter, or even a DVA attachment for your current meter if you are interested in troubleshooting your ignition system in the future.

 

[BruceAML]

Re: Using A Multimeter

It would be helpful to tell us what make and model meter you have and where it was made. I know on my Fluke 8025B there are two V for voltage setting. The V with a straight line over it is for DC volts and the V with the curved line over it is for AC volts. I am not sure if your meter has 2 voltage settings but you might want to check.

 

[HighTrim]

Re: Using A Multimeter

That is why autoranging multimeters are better for some. The central knob has fewer positions and all you need to do is to switch it to the quantity you want to measure. Once switched to V, the meter automatically adjusts its range to give a meaningful reading, and the display includes the unit of measurement, V or mV. This type of meter is more expensive, but obviously much easier to use over switched range multimeters where you have to choose which one is appropriate for the measurement you want to make.

 

[rodbolt]

Re: Using A Multimeter

Ohms testing ign coils,pulser coils,stator charge and lighting coils is nice but the defintive test is loaded Volts output.
most the time this can only be accomplished with a DVA attachment or a meter that has a DVA setting.
myself I cant afford the fluke, ya outta see a grown man cry when he takes his fluke swimming .
I do own 3 stevens CD-77,one merc analog meter with a DVA scale and something like 4 different radio shack DVMs.
I also have a radio shack DVM here in Caracas VE and one in Rio Chico VE as well as a CD-77 and a rapair DVA adapter in Rio Chico.
like AChris says, without a meter I am one armed and blind.
but certin things need an analog meter to catch,others will do just fine with an auto ranging DVM.
I used to own a simpson 260,will buy another one day.
good example of why not to loan tools.
never knew the meter face of a simpson 260 could actually be blown out of the case.
nice thing about it, Trons is Trons and it really doesnt matter who,what or where it was built.
it always works the same.

 

[Lakester]

Re: Using A Multimeter

It would be helpful to tell us what make and model meter you have and where it was made. I know on my Fluke 8025B there are two V for voltage setting. The V with a straight line over it is for DC volts and the V with the curved line over it is for AC volts. I am not sure if your meter has 2 voltage settings but you might want to check.

hello,
thanks for all the good inputs. i am using my MM more n more... mostly for temps and volts. resistance and continuity at times.

redid all the batts in my remotes last ever. tossed the 1.1 volts, kept the 1.3 - 1.4v and put the 1.586 etc into my fav remotes...

will post my model up...

regards
lakester

 

[achris]

Re: Using A Multimeter

ya outta see a grown man cry when he takes his fluke swimming .

Ain't that the truth!!!

For everybody without a DVA meter/adaptor I am going to do some research and design an easy DIY adaptor... It should only be a capacitor and resistor, but I'll have to run the numbers to get the right values (when I'm home).

Cheers,

Chris.... (stay tuned)