Choosing the Right Multimeter for Your BeagleBone

By Rui Santos, Luis Miguel Costa Perestrelo

A multimeter measures volts, amps, and resistance on your BeagleBone. It tells you what’s going on in your circuit. Multimeters come in a plethora of flavors. The main differences lie in their functionalities.

Multimeter features

Most multimeters have the following features:

  • Selection dial: When so many things fit into a little handheld device, you have to have a way to choose exactly what you want to do. Want to measure resistance? Rotate the dial to the section of the multimeter that displays Ω. The resistance section of the selection dial has various ranges to choose among, from hundreds to thousands and millions of ohms. Some even feature an autorange function, which saves you the trouble of selecting the range. You can also measure voltage and current by moving the dial to the V and A sections.

    Some multimeters can measure voltage and amperage for both alternating current (AC) and direct current (DC). This means that there are two sections featuring a V or an A. Each section has a symbol next to it: a dash with three dots below it, resembling a digital wave, for DC, and a tilde (~), resembling an analog wave, for AC. For most applications, you use DC.

    Many multimeters provide functions other than measuring voltage, current, and resistance. One common, extremely useful feature is the continuity tester. For finding out what’s wrong with a circuit, few tools do the job as well as a continuity tester.

  • Digital display: The display is where you read the values that the multimeter is measuring. You can select the range of the measurement by using the dial and/or buttons doing so moves the decimal point. Some multimeters, however, provide an autorange function.

  • Probes: The probes on the multimeter are what you stick into your breadboard to take your measurements. Exactly how you do that depends on the functionality you’re using. Typically, a multimeter comes with two skewerlike probes: one red and one black. For some applications, probes that have crocodile clips at the end can be useful.

  • Sockets: Depending on how you use your multimeter, you can plug your probes into different sockets. Most multimeters have three or four sockets. One socket is always COM, which is short for common. You always need to have a probe in this socket (conventionally, the black one), as it serves as a point of reference for your measurements. Usually, you connect it to the circuit ground (GND) or to the negative end of a component. The other sockets are labeled with one or multiple symbols.

Multimeter sockets and symbols

Multimeters have three or four sockets. Depending on what you want to measure, you have to insert your probes in the right socket. (Some sockets have more than one symbol.)

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The circuit ground is where you connect the minus (–) pole of your battery. The BeagleBone also provides a ground pin.

Some multimeters have added functionalities and display other symbols to label their sockets. These symbols are always the same as the symbols displayed around the selection dial.

Some multimeters offer features whose symbols don’t appear next to a socket. Generally, the socket responsible for measuring voltage is also the socket used for these functionalities. On this multimeter, for example, even though the VΩmA socket doesn’t feature the symbol that labels continuity testing, it’s the socket you use for that functionality.

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