How to use and read your volt meter.

Discussion in 'Electrical & Stereo' started by ttocs, Jun 12, 2015.

  1. ttocs

    ttocs Legend

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    I can't remember the first time I was shown a volt/current meter as it was a long time ago and I have been using them for since that its just second nature to me. Now on the flip side of the coin it is really easy to get confused with them and to read something wrong/blow a fuse, ect. Bear with me as I am just killing time at the hospital to do this and the drugs they give me leave me a bit loopey from time to time so this is certainly a first draft.

    reading the tutorial will give a you a start to your meter and hopefully help you to gain a little confidence to make the readings with your meters. With that being said I have to do that stupid thing to protect me and the site and say we are not responsible for any incorrect readings or damage that is done. There are more then a few meters and they each have their good/bad points I will go over for you.

    So to sum it up on test lights, they are fast/cheap/easy. You also need to be

    -Test lights and circuit testers-
    These have long been known as the cheapest and easiest way to check for voltage. They do not check resistance, current or any of the other things that a regular meter can test for but it makes checking voltage really easy.


    1.) - Here is a perfect example of how easy it is with a test light. This is the most simple version and as you see its nothing more then a 12v light. Slightly more complex designes will have some leds in it to show 6/9/12 volts. They often they look like a screw driver
    with a light in it and a ground cable that comes out the back. This one would go for $10-15.

    Stick with me on this as its still early in the process and there are a lot of little stuff to cover. If there is/are particular spots you want too see please pint thrm
    [​IMG]

    they can start out at really cheap around $20 but get up in price pretty quick for $100+ and they will work just fine for voltage. this is the one I use and love. Its small and has a nice light on the end.
    [​IMG]
    never seen this on before and it seems nice and simple.
    [​IMG]came across this one and I am considering getting it for myself as its a good price for bluepoint. never seen one like it reallu

    and then some of the higher end test lights do what the other do but also give you the option to put +/- on the wire your testing to actuate for example the door locks to test if they are working.
    [​IMG]

    ok so those are the general types unless you get into some super high end piece that can do much much more and cost more. I have been considering getting one but not sure I would use it all.

    So lets go over the test lights pros/cons.
    Pro - super easy to use an read. If it isn't reading correctly then then check the ground or the connection. Because of the simplicity of these its either the connection or the bulb.
    Pro - cheap
    pro - easy to find.
    pro - very comfortable tool that is easy to read and understand

    Cons - they will only tell you voltage unless you get one with smaller multiple leds to show what the voltage is, otherwise it reads either on or off.
    Cons - its a VERY comfortable tool right up till it slips from the wire and stabs you!
    cons - they say that most are not computer or air bag safe. I am not really sure what to think about this as I have talked to a lot of installers about it and no one actually knows anyone that has either popped the air back or smoked the ECU. There is no reason to probe/test a ai bag and a meter really is a better tool if you are measuring at the computer. So use some common sense as these are really just to make quick/easy tests and not meant to be the only meter/tester in your box.

    Newly added 12/28/2017

    I am going to be using a standard multi-meter as is shown in the pics for what I do. I got this meter in my tech school tool box my first freshman year of college(not a typo) when my the 94 was still brand new and have been using it faithfully ever since. On this meter as in many other(old meters) there is the dial in the middle, a power button and then the spot for the leads in the bottom. This meter is old enough that it is not auto-ranging meaning for example if you go to the ohm section of it(with the ohm symbol/upside down horse shoe) the numbers listed in it tell the maximum reading you expect to see. If you go above it it does not explode it just tells you the reading is over the max limit and you flick the dial up a couple of notches. Modern meters you just set it to ohms and then it will automatically set the range for you but mine as I said is older then some of you reading it. Now the multiple spots on the bottom can cause confusion but its not hard. The black never moves, it stays put and if you look next to the red spots you will see the voltage symbol, resistance symbol and next to the other you will find the current symbol. For this next part we want the red lead in the resistance spot.


    Have you ever held a harness in your hand and wondered what pin in it went to what wire? Here is a couple way to tell.

    Ohm it out - In this process we are just going to be measuring the resistance of the wire. In this case it will not matter what range I set the meter to as a piece of wire should have a very low impedance, in a perfect world it would be 0. Once the dial is set its important to make sure the meter leads are plugged into the correct spot to read resistance and the ground is in the same spot it always should be. Take a look at the meter and it should read in this case "1 . " which means infinite, or no connection. Its never a bad idea to test to make sure you have things set up right and if you touch the two leads together you will see that the display changes to a regular display with a number. The number on it is not important any reading means its making a connection. When you remove the two leads, the display will again go to "1 . ". Now take one end of the leads and connect it to the pin you want to find, and now with the other lead you can try one wire at a time. If the pin does not match your wire the display will not change from the 1 . , if it is connected it will again give a regular number and once again that number is not important, it just tells us we found what wire goes to what pin.
    Here it shows no connection
    [​IMG]
    Here it shows we have found the purple wire is connected to the pin I suspected.
    [​IMG]


    diode check - This spot on the dial is marked by the little arrow with the line on the end of it as shown in the pic. The display is going to act the same as it did in the resistance test meaning with no connection it shows "1 . " and will give a number when it connects, as well as give an audible beep. Again test this prior to starting by simply touching the leads together and the meter will beep, take them apart and it stops = meter is good.

    This shows when its not connected and would not be beeping.
    [​IMG]
    Now the test goes the same as the resistance test as well with one lead on the suspected wire, and the other on the pin. If the meter doesn't beep then switch one of the leads to a different wire/pin and keep doing this till it does beep. This way is nice because you do not have to see the display to know when its correct.
    [​IMG]

    What happens if you can't reach both ends of the harness? This happens fairly often and when it does first check all the wires you suspect goes to the pin you need and confirm that they are not connected to power/ground. If they are not then take the pin you suspect and ground it to the chassis. Now go back to the wire your looking at and connect one end of the lead to the wire, and now the other lead to ground. If it is correct the meter will beep and you can confirm it by removing the ground and the beep will stop. You found the wire/pin.
     
  2. ttocs

    ttocs Legend

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    part 2: MULTIMETERS

    This where everyone gets confused but if you break it down there are only a few things to know and watch out for. I think the biggest problem is a mix between the electrical abbreviations that confuse people and how they are measured. Most of them make sense but there are a couple that are not so simple and can easily be confused. Once the terms are all understood then its just a matter of knowing when you measure in parallel to the circuit and when you measure the circuit in series.

    First I just want to go over the terms and abbreviations that you will need toknow.

    Voltage:Vac = alternating voltage
    Vdc = Direct voltage.

    So what is the difference? Just to keep it simple here a battery supplies direct current, and your wall supplies AC current. Each one has its good and bad points from power output to how far it can be transmitted but for the automotive world we will be working with DC %95 of the time.

    Current is abbreviated as I. I am sure I was taught why they chose the letter "I" back in tech school but that was 15 years ago.

    Resistance = R or often as an ohmega symbol or a horseshoe.

    After this you can find higher end meters that measure capacitance, check diodes and transistors and even have oscilloscopes built in now. With all that being said though %95 of what you and I will do with a meter will fall into the voltage/current or resistance areas and not need a super high end meter.

    Now that we know the abbreviations needed lets get more familiar with the meter.
    [​IMG]
    Fluke meters have long been known as one of the best in the industry and its what I use. So now if I asked you what that meter was ready to measure(assuming it has test leads in it). If you look closely at the dial in the middle you can see it is pointed towards a voltage but is it AC or DC? Flukes like to designate the ac/dc difference with a squiggly line above the "V" to show it as ac voltage and a straight line with a few small breaks in it for dc. So to answer my question as to what that meter should measure fi it had leads in it? its measuring ac voltage and this can be confirmed in the screen on the right hand side where it says Vac.

    again looking around the dial in the middle You will notice that the current symbol "I" also has flukes abbreviations for AC or DC on it with the lines

    Resistance is much easier as it doesn't matter if its ac or dc.

    Now most modern or well made meters will have what is called autoranging. Prior to this the dial in the middle was further separated into different voltages/currents/resistances as limits. If you had a 10 ohm resistor you needed to check you would adjust the dial to "R"<20 ohms. if you set it up

    sorry this isn't going faster but between my health and the momstang project it keeps getting pushed back. I am hoping to have it on the road by the end of aug and it enjoy a drive for my birthday.

    Please feel free to suggest any ideas or areas that you need help with and would like to see done.
     
  3. ttocs

    ttocs Legend

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    reserved for part 3
     
  4. Cpotts13

    Cpotts13 Well-Known Member

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    Good stuff.... This should be a sticky for noobs like me!
     
  5. g36 monkey

    g36 monkey Moderator Staff SN95 Supporter

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    this will be super helpful
     
  6. 03DSGGT

    03DSGGT SN95 Supporting Member

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    Thanks for the tutorial. This will definitely help me quite a bit while working with electronics...
     
  7. 96blak54

    96blak54 Legend

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    Sticky!!!!
     
  8. ElrodKTPQ_89

    ElrodKTPQ_89 Legend

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    Sticky-icky-icky!
     
  9. 1997GT4.6

    1997GT4.6 Well-Known Member

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    Great job on the instructions and explanations Scott. I will definitely refer to these when I'm dealing with electronics.
     
  10. ttocs

    ttocs Legend

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    I am open to constructive criticism down to little typos/misspellings and all the way up to what else would you like to see? Trying to make the area as informative as possible. With all the different types of connectors out I thought it would not be bad to show the good/better/best way to do it and what connectors that should NEVER be used in a car.
     
  11. Mustanger

    Mustanger Well-Known Member

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    GOOD JOB! A little correction however ...in this paragraph the last entry says VDC instead of VAC... and possibly use the term AC VOLTAGE instead of AC CURRENT it might confuse newbies later when you show how to measure AC & DC Currents (if you do & I hope so!) Just change that part & it's perfect!!! Thanks a lot & I wish I could turn the dial & make you well! I will keep praying for a healing for you! Walt

    "Fluke meters have long been known as one of the best in the industry and its what I use. So now if I asked you what that meter was ready to measure(assuming it has test leads in it). If you look closely at the dial in the middle you can see it is pointed towards a voltage but is it AC or DC? Flukes like to designate the ac/dc difference with a squiggly line above the "V" to show it as ac current and a straight line with a few small breaks in it for dc. So to answer my question as to what that meter should measure fi it had leads in it? its measuring ac voltage and this can be confirmed in the screen on the right hand side where it says Vdc.

     
  12. ttocs

    ttocs Legend

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    Well thanks for the kind words man it honestly means a lot to me. I try not to dwell on it too much but it is daily thing as I am now typing this hooked up to an IV... Even better yet mom is on the other side of the building also hooked up with vertigo issues.. But I am going to see what I can dig up to show how to measure voltage/current on this today to kill some time. I also made a wire connection/splicing/soldering page if your proof reading any more today.
     
  13. Mustanger

    Mustanger Well-Known Member

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    You are one of the premiere members on here TTOCs! We all enjoy your posts & you have so much knowledge & so many skills! Thanks for these kind of posts that are going to help a whole bunch of folks! Keep it up as you feel like it. Doing great!
     
  14. ttocs

    ttocs Legend

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    I added a new section finally in the original post, its noted on the bottom where the new stuff begins. I have not had a chance to proof read it yet so its probably horrible as usual. Any questions?
     
  15. g36 monkey

    g36 monkey Moderator Staff SN95 Supporter

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    Good info on the ohms. I always tell people to check that when working on projects, they never have any idea what I am talking about!
     
  16. Werecow

    Werecow Active Member

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    Dude! I just got a good (for me) multimeter, if there's anything you can think of to add to this sticky I know I'd really appreciate it!! I'm reviving this cause idk if any of our newer members know of this lil nugget that they can use as a resource for their toolboxes!!
     
  17. ttocs

    ttocs Legend

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    dang photobucket screwed this one as well.