A multimeter is a test tool, mostly used in electronics, that should always be present in the FabLab of a Maker.
It is a diagnostic tool that allows us, for instance to:
There are many different types of multimeters, some with more or less features. The following image lists the parts that the majority of multimeters have.
It is hard to say exactly which characteristics a multimeter should have, since there are different needs depending on the background of the user and the intended usage, but let's say that independently of the level of the user, a multimeter should have:
Then, depending on the user background, there will be some features that could make the multimeter easier to use, or make it a more complex tool. Some of these features are:
Multimeters have different working modes, depending on what are you interested on measuring. Let's start by how to use a multimeter to measure voltage, resistance, conductivity and current.
This will require to place the measurement selector in the Volts section the black terminal in the COM and the red terminal in the V|Ω|mA terminal.
With this configuration, the selected scale should be adjusted based on the measured voltage.
If you want to measure the voltage close to a 9V battery, the scale should be 20.
In order to know what scale to select, you should check what is the approximate value that you will be measuring, and select the scale according to it:
If you try to measure a higher value than the one specified on the scale, the display will show "over-value", which is usually shown with the number "1" on the display.
Once you have selected the scale to use, it is time to use the terminals:
The image below shows how to read the voltage falling in an LED. In order to know the voltage falling on a component, you will need to connect the multimeter in parallel with it.
You can see how the black terminal checks the negative terminal of the LED, which is connected to the negative pole of the battery and the red terminal on the positive terminal of the LED.
In order to measure resistance, the measurement selector should be in the Ohm section.
The scale to measure resistance works exactly as explained in the "Measuring voltage section".
In order to know the value of a resistor, you need to keep in mind that the measurement must be done on a resistor that is not connected to any other component! Then, you can make the reading:
Place each one of the terminals of the multimeter in each one of the terminals of the resistor.
This feature allows you to know if a material is or is not conductive.
To make this test, you will need to "touch" a material with both terminals of the multimeter, once you do so, depending on the multimeter you will see:
Reading current is a little bit more complex than reading voltage or resistance. In order to make current with the multimeter, first you will need to connect the red terminal to the 10A(DCA) connector and place the selector in the A section.
Once the connections are configured, as shown above, and the selector is properly placed you can measure the current that is flowing on a circuit. Just make sure that the multimeter is connected in series with the rest of the components of that same circuit.
The image below shows how to read the current flowing through a circuit with a LED and a resistor. Here, you can see how the multimeter is connected in series with the resistor and the LED, as if it was one more component of the circuit.