Measuring amperage using a multimeter, Easier than you think…

Amperage is the unit of measure for current. Current can be defined as the amount of electricity flowing through a conductor (commonly copper, aluminium or steel)  in an electric circuit. Current is a key factor of electricity and knowing how to measure current in circuits will help us understand many things about a circuit.


Before we can measure amperage we need to make sure we have the correct equipment. For this test, you need a multimeter (which incorporates an ammeter), a pair of test probes one red and one black and a circuit to test on.

Before performing the test we must make sure we choose the amp (ammeter) option and have selected the appropriate amp setting (AC or DC) for the circuit we are testing. If the circuit you are testing is a DC circuit we will need to set the dial to DC amps and if the circuit we are testing is an AC circuit than we will need to set the dial to AC amps.

After you have selected AC or DC current, you will have to select the appropriate unit range. This will be determined by how much voltage the electrical power source has. Depending on what multimeter you have will determine what range you choose. If for example, I had a multimeter with ranges 20mA, 200mA and you had a DC load of 16mA, I would choose 20mA because it is the most appropriate for the circuit I am testing.

There may be instances where you are testing a circuit and you don’t know the voltage of the power source. In these cases, you will have to change between AC and DC and alter the unit ranges until your reading is displayed in a way that is easy to understand. If you are using an auto ranging multimeter, there will be no need to do this because this type of multimeter automatically selects the appropriate unit range for your reading.

Why you should use a Multimeter?

When measuring amperage there are a few types of measuring tools that can be used. The old method of measuring amperage would require you to use an ammeter. The problem with ammeters is that they are very old and they are not accurate. In addition to this, they can only be used to measure amperage. On the other hand,  you can use a multimeter. A multimeter can be used to measure many things such as volts, resistance and amperage. The advantage of using a multimeter over an ammeter is that multimeters are easier to use and displays its measurements in an easy to understand digital form.

Measuring amperage using a multimeter,


If you have an auto ranging multimeter, reading your measurements will be even easier than a normal multimeter meter because with this multimeter, the measurements are displayed in the most suitable unit range automatically. This means that this multimeter will automatically select the unit range which will be the easiest for you to read. Therefore, you don’t need to spend time adjusting the multimeter in order to find the most suitable unit range.  As well as this, the reading you get from a multimeter will be more accurate than reading from an ammeter.

Testing the circuit

Once you have all the necessary testing equipment (Now that you have checked everything and made sure that you have the requirement) we can move on to testing a circuit. The first thing you must do is insert the red probe in the meter socket that corresponds with amp symbol you previously selected. The second thing that you must do is turn off the circuit. After you have done this you will need to find a suitable place in the circuit to create a break. The best places to create breaks are usually places that are easily accessible to disconnect and reconnect.

Once you have done this, you will have to install the ammeter where you created the break. When you do this, the ammeter becomes part of the circuit. When the ammeter becomes part of the circuit, electricity is able to pass through it just like any other component in a circuit. After, you have installed the ammeter, you will have to turn on the circuit. Once the circuit is turned on, the ammeter will measure how much amperage is in the circuit.

These are all the steps you need to follow in order to measure amperage. As you can see, this process is very quick and  can be done by anyone.

Cautions of using an ammeter

One of the the things you need to be cautious of is causing an electric short by hooking up the ammeter in the wrong way. Causing a short by hooking up the meter in the wrong way will normally blow a circuit’s fuse or the meter’s internal fuse.

Whilst current testing, you need to be aware the ammeter acts as a pair of jumper wires with a measuring device in the middle. If you’ve ever accidentally touched jump leads together whilst being connected to a 12V battery positive (+) and negative (-) terminals you’ll know what happens! It is what we call an electric short. An example of hooking the meter incorrectly, is when you place the ammeter across a device in a live circuit or you place it across any type of power sources. You will defiantly cause a short by doing these things and you could possibly damage your multimeter.

One of the things many people do, especially people who are new to using a meter, is that they use an ammeter like a voltmeter. As I mentioned before, an ammeter is like a pair of jumper wires, whereas as voltmeter is not and can be used to to test voltage across a power source or a device in a live circuit. When you do this with an ammeter, you are creating a short from the positive side of the circuit to the negative side. If your circuit does not have a fuse, then you damage the whole circuit by using the ammeter in this way. You need to be careful and make sure you don’t make this crucial mistake.

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