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basketcase and the art of reading a multimeter
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basketcasebear Offline
#1 Posted : Friday, 22 May 2009 4:00:09 AM(UTC)
basketcasebear

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hey yall,
am endouvouring to ascertain whether i have a slow elec leak or a buggered battery,
so have purchased a brand spanking new multimeter, of the highest quality,, trouble is, i have no bloody idea how to use it. [typical basketcase]
so could someone help explain the following>>
1, where do i put the red and black wires into which holes, there are three,
2. do i turn the dial onto,, DCA, or DCV, ?
3. then what do i do to find if a circuit is losing volts/amps.
apreciated muchly, all your replies.
cheers
bcb

it was but yesterday, i thought myself a fragment, quivering without rythum in the sphere of life.
now i know i am the sphere, and all of life quivers in rythmic fragments, within me!
kg.
more than basketcase than a bear!
DOH!!!
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ozchevy Offline
#2 Posted : Friday, 22 May 2009 4:23:44 AM(UTC)
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What brand is it bear?
Does it have a model number you can post here?

I use these things everyday (Im an industrial Electrician)
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HQforme Offline
#3 Posted : Friday, 22 May 2009 4:28:20 AM(UTC)
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A brand new multimeter should have brand new instructions with it! Failing that, google it.

To test the battery, id disconnect it completely, charge it, and measure the voltage drop over several days. It shouldnt drop much if its healthy.

To test a circuit, im not 100%, but no component shouldnt be drawing if the cars off, except for alarms and things like head unit permanent power.

Most likely if powers draining then theres a short so youre just looking for frayed connections or exposed wire. However if a unit or switch has shorted internally then it could be drawing current. Youre looking for current at the active side of a component when its not switched on.

Thats speculative though, so well wait for somone who actually knows their stuff to come along and advise :-)
"Silly modern cars"
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ozchevy Offline
#4 Posted : Friday, 22 May 2009 4:47:27 AM(UTC)
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Id leave the battery connected. Set the meter to DC Volts - Red test lead to battery (+) Black test lead to battery (-)

Measure the voltage across the battery terminals with no engine or ignition on. Just the meter and see if it changes. If you have a car clock fitted or any device connected straight to battery without going through the ignition - it will draw a small amount of juice from the battery over a period of time. You can measure how much voltage is lost in millivolts or volts over one hour.

Edited by user Friday, 22 May 2009 4:48:01 AM(UTC)  | Reason: Not specified
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basketcasebear Offline
#5 Posted : Friday, 22 May 2009 5:22:27 AM(UTC)
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thanks chevy/hq4me.

it is a projecter digital multimeter.
it did not come with instructions

i had put it on dcamps, and it sparked? when i put it on terminals.
i will put it on dcvolts, and have a captain cook,
considering the incredible and extremely complex automatic gizmos i have wired into the camperer, it will not surpise me if one circuit has a prob.
which one,,"that is the question". i will endeavour to find out.
i will get back, once i knows i am finding a drop without anything on,
if not, it is the battery that is cactus,
cheers
bcb



it was but yesterday, i thought myself a fragment, quivering without rythum in the sphere of life.
now i know i am the sphere, and all of life quivers in rythmic fragments, within me!
kg.

Edited by user Friday, 22 May 2009 5:26:32 AM(UTC)  | Reason: Not specified

more than basketcase than a bear!
DOH!!!
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Custom Offline
#6 Posted : Friday, 22 May 2009 6:23:39 AM(UTC)
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I am a sparky and I find it hard to believe you have an electrical leak, the only thing that will cause that sort of thing is current being drawn on the circuit, ie a globe being left on, an alarm drawing a small amount of current. Heres a tip, a car battery in good nick should be able to run a car radio for at least 8 hours or draw 2-3 amp for that period of time.

Instead of guessing at it yourself just take the car down to you local Ultra Tune or K Mart Auto where they will have discharge unit they can hook up to it and see how its holding up. Batteries are pretty cheap these days anyway and with the colder weather aproaching you will be using more electrics in the car and it will only get worse.

Good luck.
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Browno Offline
#7 Posted : Friday, 22 May 2009 8:27:08 AM(UTC)
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got the same problem in one of my cars.. not saying wat make haha, and ive put it down to mods in the wiringloom , if im working in the engine bay and have my legs on the bumper i can feel a slight tigle from it earthing out yeah?

Drive It Like You Stole It......Drive it like you own it
Drive It Like You Stole It......Drive it like you own it
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johnperth Offline
#8 Posted : Friday, 22 May 2009 8:53:11 AM(UTC)
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you should also buy a battery hydrometer, Big W sell them for about 4 bucks they have the instructions and are dead easy to use, will tell you straight away the condition of the battery.
Wont tell you if the battery is flat because its buggered or because you have a dud alternator or short, but will tell the condition of the cells.
Takes a bit of practice to read a multi meter properly . but the quickest way to be sure is go to the local tyre or battery joint and they will do it.
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roy1126 Offline
#9 Posted : Friday, 22 May 2009 8:57:39 AM(UTC)
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Basketcase

If you had the multimeter on dc amps and the leads plugged in the current measuring connectors, then considering you said you got a spark, I will suggest your multimeter is no longer brand new.
What you have effectively done is short across the two battery terminals and therefore I would say the internal protection fuse of the multimeter is blown.
This will still allow you to measure volts (with the leads in the correct connectors) but until the internal fuse is replaced you will no longer be able to measure current.
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basketcasebear Offline
#10 Posted : Friday, 22 May 2009 11:11:30 AM(UTC)
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hey thanks all for input,
i cant take it to local place to be looked at,
i hope i havent blown the meter, but how does one know which wire goes in which hole??
i think the middle one is ohms.
i have them in outside holes
so why it would spark?? dont know??
it is probably battery, just want to check first,
cheers
bcb


it was but yesterday, i thought myself a fragment, quivering without rythum in the sphere of life.
now i know i am the sphere, and all of life quivers in rythmic fragments, within me!
kg.
more than basketcase than a bear!
DOH!!!
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bosko Offline
#11 Posted : Friday, 22 May 2009 11:25:11 AM(UTC)
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what does it say next to the holes

it probably has a com port for black lead (earth, negative) and a v/ohm/hz for red lead (+) if you want to measure volts

other holes would be amps or ac stuff i guess
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basketcasebear Offline
#12 Posted : Friday, 22 May 2009 10:46:17 PM(UTC)
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hey bosko,
it has three holes, com bottom earth?
top says 10a dc [red?
i am going to put it on the different curcuits going to the diff elect motors, i have put in, seats winches,windows etc, see if they are okie dokie,
then if all is well, it is battery
thanks for reply
cheers
bcb

it was but yesterday, i thought myself a fragment, quivering without rythum in the sphere of life.
now i know i am the sphere, and all of life quivers in rythmic fragments, within me!
kg.
more than basketcase than a bear!
DOH!!!
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basketcasebear Offline
#13 Posted : Saturday, 23 May 2009 2:04:09 AM(UTC)
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hey yall,
i put this meter on the battery, with red in top, black in com bottom, and thru it on the battery and the earth wire got rather warm, sparked a tadd?? it is still showing numbers when i turn it on, so i think it is hunky dory.
but something is a tadd wrooonn wrruoong still cant say that word..
uumm
what am i missing here?
cheers
bcb

it was but yesterday, i thought myself a fragment, quivering without rythum in the sphere of life.
now i know i am the sphere, and all of life quivers in rythmic fragments, within me!
kg.
more than basketcase than a bear!
DOH!!!
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kraul Offline
#14 Posted : Saturday, 23 May 2009 2:20:04 AM(UTC)
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when measuring volts u go in parael to the load and when measuring current you go in series. If u do it the wrong way you wil either blow a meter fuse or damage what you are working on.
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basketcasebear Offline
#15 Posted : Saturday, 23 May 2009 3:57:46 AM(UTC)
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hey kraul,
i have no idea what you mean by paralel and series.?
does series mean>> i put the red and earth wire on the wire i am trying to measure?
and paralel from the wire to earth?? or vica versa??
learning learning learning?
cheers
bcb

it was but yesterday, i thought myself a fragment, quivering without rythum in the sphere of life.
now i know i am the sphere, and all of life quivers in rythmic fragments, within me!
kg.
more than basketcase than a bear!
DOH!!!
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kraul Offline
#16 Posted : Saturday, 23 May 2009 5:49:12 AM(UTC)
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ok.
Black wire always stays in com that the negative side of the meter
The top two are for different jobs
The 10a dc on is for when ur measuring amps and nothing else, To use that u have to disconnect the suply wire + wire to what ur testing and put the meter in the line so the red meter lead is on say the battery and the red wire goes to what u have disconected. This then completes the circuit so what your testing will now operate. But as its only able to go to a max of ten amps only test Accessories as they have a low current draw. Personly i dont like this way of testing because its annoying and u have the risk of shorting the active to earth and thats bad! Thats why clamp meters are great for testing current draw. Thats all il use.
For testing voltage put your red lead in the middle hole and the black in the common.
Testing voltage is easy. For testing your battery all you have to do is put the red lead on positive terminal and black lead on negative terminal. And you have ur reading.
Its the same for other things, for a relay base go to the positive terminal and to earth and its show voltage.
But remember that voltage is potential difference so if u put one lead on the positive terminal and the other on another live positve wire it will show zero volts as they are both at the same potential. Simply always test to earth.
Obviously when testing amps have the meter switched to dc amps and when testing volts have it set to dc volts if it doesnt have dc written there the symbol is a solid line with dots under it

For detailed info have a read of this http://ecmweb.com/mag/el...ics_digital_multimeters/
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basketcasebear Offline
#17 Posted : Saturday, 23 May 2009 6:10:03 AM(UTC)
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thankyou thankyou thankyou, kraul,
i am sure i will be able to checkensi out if i have any leaks, hope?
it could be i have wired one of the wiper motors in wwwrrrooonn,, [still cant say it]
i know they are earthed, and maybe should not be?
not sure?

I am aliitle confused though about what to do to check whether i have a leak in one of my curcuits?
i think you said i have to disconnect whatever i am testing?
i thought i would need it connected to see whether it is drawing current even when turned off??
so i am still confused, i read a little of the website you gave, and it is all a tadd too much,
i only have one red wire one black, so black goes on ground.?
and red goes on curcuit i am testing?? not sure about this part?
need just a tadd more explanation on that part, i will test the volts, that sound easy,

will let you know how i go,
thanks again owe ya.
cheers
bcb

it was but yesterday, i thought myself a fragment, quivering without rythum in the sphere of life.
now i know i am the sphere, and all of life quivers in rythmic fragments, within me!
kg.

Edited by user Saturday, 23 May 2009 6:45:22 AM(UTC)  | Reason: Not specified

more than basketcase than a bear!
DOH!!!
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kraul Offline
#18 Posted : Saturday, 23 May 2009 6:30:36 AM(UTC)
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id be checking stereo, relays and other litle things. My cd player if left on standby flatens my batery in 2days.
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bosko Offline
#19 Posted : Saturday, 23 May 2009 7:01:32 AM(UTC)
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check ammeter is working and you know how to measure current

get an automotive type globe, preferably in an old socket with a couple of wires hanging out

sett multimeter to DC amps

connect red probe to batt +, connect black probe to one globe wire. connect other globe wire to batt neg

check for reading on ammeter of around an amp or 2

ok ammeter works and you know how to use it.

turn off ignition, headlights, any other major power items

disconnect batt+ lead

connect red probe to batt +, black probe to + battery LEAD

check for any current

if there is current flow then something is drawing power

if there is no reading, turn on interior light (or similar NOT headlights) and make sure you get a reading.

if ammeter works correctly and goes to 0 with interior light off you have no leakage

i always confuse black/red, on a DMM it will just read negative anyway

Edited by user Saturday, 23 May 2009 7:42:51 AM(UTC)  | Reason: Not specified
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Custom Offline
#20 Posted : Saturday, 23 May 2009 7:10:23 AM(UTC)
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And once you are done you can give Bosko an anal probe, it will take some of the stress away.

Mr Pink will thank you for it.

Goodo then.
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