# Measuring voltage, current and resistance using a multimeter

> Learn how to measure voltage, resistance, and current with a digital multimeter, including why current must be read in series while the rest go in parallel.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2020-12-27 | Topics: [Arduino](https://flaviocopes.com/tags/electronics/) | Canonical: https://flaviocopes.com/electronics-measuring-with-multimeter/

A digital multimeter is a handy tool, one of the few tools you'll need to start with.

There are many kinds of multimeters, from very cheap ones (~10$) like this which was very cheap to buy but also has a very cheap feeling:

![Cheap yellow digital multimeter with blue display showing basic voltage, current, and resistance measurement controls](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2940.jpg)

Unless you go on a very professional line, which you don't need to start with, you can get a great one for < 30$.

I paid this 30$ and it's very well made:

![High-quality red and black AoKoZo digital multimeter with LCD screen and test probes, showing better build quality](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2942.jpg)

Between those 2 there's a big difference in size and build quality:

![Size comparison between small yellow and larger red digital multimeters showing different port configurations and features](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2952.jpg)

You can also see one has a `10A` port, and the other has a `20A` port. This means one can measure up to 20 Ampere of current before breaking its fuse, the other half of that.

The mA port can measure up to 500mA in the bigger one, 200mA in the smaller.

Also, one can measure temperature as well with a special cable. It has a light, and so on.

A digital multimeter can measure voltage (**voltmeter**), current (**ammeter**), resistance (**ohmmeter**), capacity, frequency, and more.

It's a lot of tools built into one.

I'll show you how to measure the first 3 things.

## How to measure voltage

Let's start by measuring voltage. Take a battery, connect select the `V` symbol:

![Close-up of multimeter rotary dial set to voltage measurement position with V symbol highlighted](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2959.jpg)

and connect the black connector to `COM`, the common ground, and red connector to the `V` symbol, then connect the other end of the cables to the `+` and `-` battery terminals:

![Digital multimeter connected to 9V battery with red and black test probes measuring voltage, display showing 8.94V](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2958.jpg)

![Yellow multimeter measuring voltage of 9V battery showing 8.75V on LCD display with finger pointing to result](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2962.jpg)

## How to measure resistance

Now let's see how to measure resistance.

Connect the two cables to the two ends of a resistance, and select the `Ω` symbol on the multimeter:

![Red multimeter measuring resistance of 220 ohm resistor, showing 220.1 on blue LCD display with dial set to ohm symbol](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2970.jpg)

It's a 220Ω resistance.

Here's the same measurement on the cheaper multimeter:

![Yellow multimeter measuring same 220 ohm resistor showing .22 on display with manual scale selection required](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2966.jpg)

Notice that previously we didn't have to set the scale, it was automatically determined. Here if the resistance is too low or too high for the scale you need to tweak it between the `200` `2000` `20k` `200k` `2000k` points to see which one gives you a meaningful result.

For example here I picked the `20k` scale, and I got `0.22` in the display. `20k` means it can measure up to `20kΩ`. 0.22 in this case means it's 0.22 of 1kΩ:

![Yellow multimeter with dial set to 20k resistance scale showing proper reading for 220 ohm resistor measurement](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2967.jpg)

Slightly confusing, right? It's not optimal, so I recommend you pick a multimeter that can determine the scale automatically.

## How to measure current

I showed you how to measure voltage and resistance first, because they work in a similar way: the connectors are put in parallel to the item we want to measure.

Measuring current is different. We need to put the multimeter in series, making current flow through it.

Also, depending on your multimeter, you might need to change the entry point for the cable. In this case I measure volts and Ω using the input #4, but current is measured using input #1 (and high amounts of current through input #2):

![Close-up of multimeter input ports showing different connections for measuring voltage, current, and high amperage](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2980.jpg)

To measure current let's build a little circuit. In this case I have a potentiometer that lights a LED.

![LED circuit on breadboard with potentiometer and 9V battery showing 0.76mA current measurement on multimeter display](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2972.jpg)

The two cables connect the LED cathode to the lead that closes the circuit to GND. This is important: you don't measure the current flowing through an element by connecting the multimeter to its cables directly. You need to make the multimeter part of the circuit.

![Close-up of breadboard LED circuit showing multimeter probes connected in series to measure current flow through the LED](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2973.jpg)

The multimeter acts as a wire.

On the multimeter you can choose the scale for the current measurement. We set it to `mA`, but try switching to `uA` to measure it in microamperes instead of milliamperes:

![Red multimeter displaying 753 microamperes current measurement from LED circuit with scale changed to microamps](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2974.jpg)

You got `753uA`, which are equal to `0.753mA`.

Here's the same measurement using the yellow multimeter, in this case the port to measure small currents is the same as the one we used for voltage and resistance:

![Yellow multimeter measuring same LED circuit current showing 0.75 on display using same port as voltage measurements](https://flaviocopes.com/images/electronics-measuring-with-multimeter/IMG_2976.jpg)