Tool Tutorial: Multimeter

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Tools & Materials
Material List
  • one AA or AAA battery
  • one 9V battery
  • one 3V coin battery
  • LED (light emitting diode), 3mm or 5mm, any colour
  • assorted objects of different materials (wood, plastic, aluminum, iron, paper, etc.)
  • Optional

  • a simple circuit with a low-voltage battery, such as a tv remote or similar
Tool list
  • Multimeter

    What's a multimeter used for?

  1. Electricity is a complex phenomenon! Multimeters have two “leads” and many settings that you can use to figure out measure all sorts of things within electrical circuits.
  2. Electricity needs a continuous circular pathway (usually of wires) from the energy source to the device (light bulbs, heaters, electric motors, etc.) and BACK in order to flow. If there is a break in this pathway, or “circuit”, then no electricity will flow, and your devices won’t turn on! If you are an automotive service technician and you are trying to figure out why a car horn doesn’t work, you can use your multimeter to test the circuit to figure out which part is broken or disconnected.
  3. Multimeters are “voltmeters”, which means they can measure voltage (in volt units). Measuring the voltage of a battery is like measuring water held behind a dam: it gives you an idea of how much potential energy is available to make electricity.
  4. Multimeters are also “ammeters”, which means they can measure electrical current (in Amp units). Current is a measurement of the amount of tiny, charged particles that flow past as electricity is moving through a wire or object.
  5. Multimeters are also “ohmmeters”, which means they can measure how much resistance (in Ohms, or Ω units) an object has. Resistance is a measure of how easily electricity flows through an object or material; an object with high resistance doesn’t allow electricity to pass through it very well. An object with low resistance allows electricity to flow easily through it.
  6. Safety considerations

  7. Measuring circuits with low-voltage batteries such as AAs and 9Vs is very safe, as the amounts of energy are not enough to harm you. DO NOT touch your multimeter to household outlets, switches, or any devices that plug into household electricity. The electricity that comes from the outlets in the walls of buildings is much more energetic and a different type of electricity. Electricians receive extensive safety training before they can work on wiring, and they know how to turn the electricity off before they work.
  8. Do not operate your multimeter or the electrical circuit if any parts are wet.
  9. Read the your manual for more safety details about your specific multimeter.
  10. Operating a multimeter

  11. Have you ever tried to switch on a device like a flashlight but it wouldn’t light up? Which part of the device is broken? A multimeter can help you troubleshoot these kinds of electrical problems!
  12. For all the activities in this lesson (testing voltage, continuity, and resistance), plug the multimeter’s red cord in the “VΩ” port, and the black cord into the “COM” port.
  13. Testing low voltage batteries:

  14. First, when testing a battery to see if it has enough voltage, switch the knob to “V” (try the 20 setting). Keep in mind: depending on which terminals you touch the leads to, your multimeter might show the voltage as positive or negative. Because both lead orientations will give you the same voltage value, it doesn't matter which lead goes where to check your battery's voltage. Can you figure out what colour lead needs to touch the positive battery terminal to make the voltage read positive?
  15. Testing an AA battery

  16. Touch the lead points to the battery’s terminals as shown. If the display reads any less than 1.3V, then you have found your problem: your battery is dead! A new AA battery should measure about 1.5V.
  17. Testing a 9V battery

  18. Touch the lead points to the terminals on the top of the battery. A new 9V battery should measure about 9V. If the display shows 6V or less, your battery is dead.
  19. Testing a 3V coin battery

  20. Touch one lead point to the side of the battery with the + sign, and the other lead point to the opposite side. A dead battery will read 2.7V or lower. A new 3V battery will read (you guessed it) close to 3V!
  21. Testing an LED

  22. Check that your LEDs work before you insert them into circuits (they can often be broken or burnt out). Switch the selector knob to the continuity symbol (it looks like a sideways wifi icon - see the GIF for details). You can also use the setting with the diode icon (it looks like a right-pointing arrow with a vertical line across it).
  23. Touch the lead points to the wires that point out of the LED. If your LED lights up and/or you hear your multimeter beep, then your LED is working!
  24. If your LED didn’t light up and/or you didn’t hear a beep, don’t give up just yet. LEDs are directional: they only work when electricity is flowing in one specific direction through them. Try turning the LED around to make the electricity run in the other direction through the bulb: if you still don’t see it light up or hear a beep, then your LED is likely broken.
  25. Checking for continuity in a circuit

  26. If there is a break in continuity where the parts of a circuit are not touching, electricity won’t flow. You can test battery powered devices such as a tv remote, or you can test your own circuits you make (see the electrical projects on our Skills Ready website for examples).
  27. First, unhook whatever battery you have attached to your circuit. Switch the selector knob to the continuity symbol (it looks like a sideways wifi icon).
  28. Test your circuit by touching the lead points to different metal parts in the electrical pathway. If you hear a beep, the two points are connected and will allow electricity to flow. If you don’t hear a beep, check for breaks in the circuit (for example, an alligator clip may have accidentally unclipped itself from a wire).
  29. Testing objects for conductivity

  30. Are you curious which types of objects and materials are good conductors of electricity? Which types of materials resist the flow of electricity? Set your multimeter to the same settings as you did for checking continuity. Test different objects by placing your lead points on either side of the object. If you hear a beep, then the object conducts electricity! If you don’t hear a beep, your object has low conductivity.
  31. Environmental considerations

  32. Multimeters are usually plastic. If treated gently and used properly, they should work for many years. Dispose of used batteries from your multimeter and your electrical projects in an approved drop-off location in your community instead of throwing them out.
Extension Challenges
  1. Practice your troubleshooting skills with a buddy. Choose one of the simple circuit electrical projects from our Skills Ready projects menu, such as Pick the Booger, or the Simple Electric Motor. When you have the circuit working, take turns covering your eyes while your buddy unhooks one of the connections. Use your multimeter to check for continuity between different parts of the circuit until you find the disconnected section to fix it.
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