The Not So Scary MultiMeter


The Multimeter, or voltmeter as it is commonly known, is a nifty tool that every tinkerer needs in their arsenal.  They may look scary at first glance, but once you understand how to use one, you will find yourself going around and testing everything in the house.  You must remember that you will be working with electricity and extreme caution should always be used.  The ability to properly use a multimeter is essential to any hobby tinkerer.

Some multimeters are very expensive, but for us hobby tinkerers, a cheap one will do just fine…especially is you are just starting out.  If you are lucky enough to live near a Harbor Freight, you can pick one up that will work well enough for around $10. 

MultiMeter Layout

No matter what kind of multimeter you wind up with, it will come with two wire leads.  One is red, which is the positive lead, and one is black, which is the negative (or ground) lead.  There are three connection jacks on the multimeter.  They are marked:

  1. 10ADC
  2. VΩmA (volt / Ohms / milliamp)
  3. COM

The black lead always plugs in the connector on the multimeter called “COM.”  The red lead can connect in two different connectors.  If you are measuring Volts, Milliamps (current) or resistance, you should connect the red lead to the VΩmA connector as long as the current is under 200mA.  If you will be measuring Amps (current) above 200mA, you should connect the red lead into the connector marked with 10ADC. Multimeters are equipped with a fuse to protect against over current.  It is designed to blow if you attempt to test more current than they are rated for.

MultiMeter Connection Ports

Multimeters come in all shapes and sizes.  There are two different kinds of multimeters – Analog and digital.  Digital multimeters have a numeric digital or LCD readout, and an analog multimeter uses a needle which pivots across the voltages and the needle stops at the correct voltage.  The digital multimeter, in most cases, is more accurate….especially if exact measurements are needed.  They are always immune to parallax errors since they simply display a number.  Parallax errors occur when you look at a multimeter from an angle.  From an angle, a particular voltage can look different than it actually is.  If you are new to hobby electronics, you will also find that that the digital type multimeter is much easier to read than an analog one.

analog vs digital multimeter

Multimeters are used to measure two types of electrical current.  AC and DC…no, I am not talking about the rock band.

AC is short for Alternating Current.  In an AC circuit, current will occasionally change directions.  This is the current that is used in houses to power televisions and lights.

DC is short for Direct Current.  In a DC circuit, current only flows one way.  It flows from positive to ground.  DC is used in anything that runs on batteries.  Your car and Ipod are both examples of DC current.

HOW TO MEASURE CONTINUITY

Continuity is a very important check as it makes sure there is a connection between two points.  You can use it to find bad solder joints in a circuit or to see if a wire is broken in your project. 

  • Connect the black lead to the COM port.
  • Connect the red lead to the VΩmA.

continuity check

  • Turn the rotary knob to the continuity section.  It will look like the diode symbol.  Some meters also have a symbol that looks like a sound wave on it.  Turn on the multimeter.

The meter should read 1 without touching anything indicating there is no continuity.  Touch the black and red leads together and you should see the numbers on the LCD readout change to a number other than 1.  On some meters you will actually hear a beep.  If the number changes from 1 or you get a beep it means the two points you are testing are connected.  Try it with a regular piece of wire; put the leads on either end of it and you should get the same result.  If you have a wire that has a few smaller wires in it, try touching different wires on either end till you find the same wire at either end.  It can be challenging and fun.

You can now start checking your circuits to make sure the correct points are properly connected.  This is probably the most used setting that a hobby tinkerer uses when troubleshooting a circuit.

HOW TO MEASURE RESISTANCE

Resistors are one of the most common electrical components in any circuit.  They are very important because the resist the flow of electricity through a circuit.  Resistors come in several varieties but the two most common one are three or four colored bands that represent a certain resistance.  You can use one of the many online resistance charts or you can break out your trusty multimeter and find the value.  That’s what we are going to do today.  Most people store their resistors in separate compartment bins labeled with the resistance value on them.  I like to throw all my resistors together in one bin and use a resistor calculator or a multimeter to find the value when I need one. Let’s look at how easy it is to find the resistance of a resistor.

  • Connect the black lead to COM.
  • Connect the red lead to VΩmA.

measure resistance

  • With the meter off, turn the rotary knob to the “Ω” setting and select a high setting like 20kΩ.  This is a good starting point.
  • Turn on the multimeter and the digital readout will display 0.
  • Get any resistor and touch the black lead to one side of it and the red lead to the other side of it (it does not matter which side you connect the leads to as a resistor is not polarized and will work in any direction).

You should see a number on the digital LCD readout.  If it reads 1 or OL, it means it’s overloaded and you will need to change to a higher setting like 200kΩ or even 2MΩ.  If you get a reading of 0 or something close to it, you will need to switch to a lower setting like the 2KΩ or even 200Ω.

Once you get your number readout, compare it to the resistor chart and see how close it is.  While comparing the numbers, keep in mind that most resistors have a 5% tolerance so as long as the number is close….ya done good!

HOW TO MEASURE VOLTS

Measuring volts will become second nature to any hobby tinkerer.  When you measure volts, simply place your leads across the two points you want to measure.  Place the red lead on the positive side of the point you want to measure and the black lead on the negative side of the point you want to measure.  Don’t worry if you accidently switch them around; you will get the same result but with a – on the digital read out.  Simply switch the leads and you will get the correct readout.

measure volts

  • Connect the black lead to COM.
  • Connect the red lead to VΩmA.
  • With the meter off, turn the rotary dial on your multimeter to DCV section and select 20 (20 Volts).  This will measure any voltage below 20 volts which should be good enough for most hobby tinkerers.
  • Attach the black lead to ground on your circuit.
  • Connect the red lead to the point at which you want to check the voltage.
  • Turn on your meter and note the voltage.  Remember if you have the leads switched around, you will get the same reading but with a – in the readout…Simply switch the positions of the leads for the proper readout.

Done….That was not so bad.

HOW TO MEASURE CURRENT

The electrical current running through your circuit is measured in amperes.  It is commonly shown as Amps.  When you measure current, you have to setup your multimeter inline in the circuit so that the current flows through the multimeter actually making it part of the circuit.  Keep in mind that it does not matter where in the circuit you set up your meter…You will get the same result.

measure current

  • Connect the black lead to COM.
  • Connect the red lead to VΩmA if measuring below 200mA or connect it to 10ADC if measuring above 200mA but below 10 Amps.
  • With the meter off, turn the rotary knob to DCA and select a number that is above the expected Amps.
  • Like the picture above, connect the common lead to the negative side of the battery.
  • Connect the red lead to the middle pole of the Potentiometer (variable resistor). Your meter is now embedded into the circuit.
  • Turn on the meter and you will see how much current is running through your circuit.

 

LET'S WRAP IT UP

Wow, see how easy that was?  Now you know the basics of how to use a multimeter.  You can now go out into the world with your newly acquired skills and start doing some testing.  You will find yourself testing everything in the house.

To recap, you now know how to choose a multimeter, how it is connected, how to check continuity, how to measure resistance, how to measure volts, and how to measure current.  Sure, you can do more than just these tasks with it, but now you have a basic understanding…Now go show off your new found skills.

If you have any questions or comments, please use the comment box below.  If you found this tutorial useful, please like Tinker PlayGround on Facebook and Google+.

The next part in this beginner series will tackle some legislature passed a long time ago called Ohms Law.

Happy Tinkering