Multimeter

Multimeter Lecture (Video 4/4 in Circuits and Electronics Series)

Highlights

  •     A multimeter can measure voltage, current, and resistance and even handle AC power in some cases
  •     A multimeter is a good tool to identify faulty circuit components
  •     When measuring current, try the high current setting first
  •     Do not short out circuits!
  •     Be careful when working with high voltages and currents
  •     Protect your hands, fingers, etc. from moving electromechanical parts.

Kit Activity

If you’d like to get some hands on experience with a multimeter, try our Multimeter Kit Activity

Notes

Multimeters are used to measure voltage across circuit components, resistance, and the current in a wire. This is extremely useful in figuring out what component is misbehaving in a circuit. They can also be used to measure voltage output of a battery, which is very useful in determining whether a battery is charged or not. A multimeter is probably the minimum equipment you need to diagnose and repair an electric gadget.

Multimeters are connected to the circuit using two leads (probes). One lead will be designated as the “ground” and is usually colored black or another dark color. Sometimes the letters “COM” are next to this port on the multimeter. The ground lead is connected to the negative side of the voltage. The other lead is connected to the positive side of the voltage in the circuit is usually bright red colored. The colors are fairly standard throughout the industry. You will find the same red and black colors on your car battery as well for example.

IMG_0311

When measuring voltage across a circuit component, the multimeters kind of “hugs” the component. This way, the same voltage felt by the component will be felt by the multimeter as well. We call this arrangement a parallel arrangement. In the picture below, the diagram on the left is suitable for measuring the voltage across a resistor.

MultimeterArrangements

If we wanted to measure the current passing through the circuit, then we would connect the multimeter in a series arrangement. All the current that passes through the component will also pass through the multimeter. In the picture above, the middle diagram shows the measurement of current through the resistor.

Finally, the resistance is measured when the multimeter is connected to a resistor in isolation. Here we do not probe a circuit but only a component. You can think that the resistor and the multimeter form a circuit of their own. The right diagram in the picture above shows that arrangement.

You can use our interactive virtual simulator below to try a few experiments with what you have learned.

 

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Additional Information

To learn more, visit one of these recommended website below, or simply search the internet for the terms introduced in this lesson!