How to Measure Current (Amperage) Using a Multimeter
As a car owner, you must be knowledgeable of how to test your car’s oil pressure, tire pressure, fluids, and more. One of the most important things to check in your car is its electrical circuits, since these have a huge impact on your car’s performance.
A multimeter is a handy tool that can measure many different things. It is used for testing electrical circuits and measuring voltage, current (amperage), resistance, continuity, and other quantities. Multimeters are handy because they have multiple functions in one device. However, it can be challenging to remember using each function if you don’t know the full name. Here’s an article about how to measure current (amperage) with your multimeter!
Types of Multimeter
There are two different types of multimeters: analog and digital. An analog multimeter uses an internal meter movement that measures current, voltage, or resistance. A digital multimeter has a numeric display to show measurements in numbers instead of having an internal moving part for each measurement function. Analog meters tend to be less expensive than digital meters because they use fewer parts. However, it’s hard to see your readings clearly if you’re not strong at reading small scales on instruments like this. Also, there may be “ghost” images left by previous measurements due to residual magnetism when using analog devices. This effect can make it difficult for you to get accurate results with your device.
You can use a multimeter to measure the voltage of an object. This might be necessary to make sure electricity is running through it. You can also use it to see how much resistance there is in a wire that might not be working correctly. Today we are talking about measuring the current in an object or how much amperage in a wire.
It is less common to measure current than it is voltage or resistance. If a circuit does not work, it may be because there is no power supply, the path for the current to flow has been blocked, or a part of the circuit is bad. You might need to find out how much current is flowing in the future. But usually, you won’t need to measure it. We will get back to that at the end of this article.
Current measurement is different from a voltage or resistance measurement. Voltage and resistance are measured when power is not provided to the circuit. For example, using a water meter will calculate how much water flows through it with the power off. Current measurement is made with power on and in series with all of the other circuits in a circuit. It’s like measuring how much water goes through your house by sticking a meter at your home.
You need to reconfigure the meter for measuring amperage. You need to use a different socket than the one you used for voltage and resistance measurements.
There are usually two sockets. You need to choose the correct socket, or else there is a possibility that your meter will break.
You should always measure the current. Current is the unit of how many amps there are. The meters have a dial and sockets that aren’t labeled “C.” They’re labeled “A” for amperage.
Multimeter Configuration Stages
Set the multimeter to measure the current after turning it on. There are three configuration stages:
- There are two types of sockets on the device. One is labeled “COM,” which means it is like all other measurements. You only need to place the black probe in that socket once, and you won’t have to move it again.
- Place the red probe in the amperage socket labeled “A.” There are two sockets on the meter. One has a 10A printed next to it, and one has 300mA next to it. When you are not sure, but the red probe in 10A.
- Turn the dial to the type of socket you are using. This will be different from meter to meter. For example, there may be individual settings for “A” and “mA” sockets, or there might only be an “A” setting on the dial. If you’re not sure, ask someone familiar with your meter.
A multimeter is used to measure electricity. You can measure high amperage or low amperages with it. The red probe goes in the “A” socket, and you turn the dial to the A setting.
There are different types of meters. Some meters have an internal fuse in the low amperage socket but not in the high amperage socket. This means that if you use a meter with no fuse for a 20 amp circuit, it will blow up.
You should cut an end of the wire and attach it to the meter to measure the current in a circuit. Connect the wire’s other end to your meter if you don’t want to miss anything. You will need this for measuring the current.
Before you connect the meter, turn off the power and use alligator clips. When you use the pointy meter, the current will flow through it. Because of its limited surface area may cause it to heat up and weld to whatever you’re testing. But if you use alligator clip leads, this won’t happen because the load is spread over a larger area. Attach them to a power source and test.
Connect the meter as low as possible on the ground side of the circuit. When you replace a battery in a device, you should always disconnect the negative (black in most cases) and connect it last. When measuring current, the meter is in series with the circuit, so the probe leads are “live” when measuring the electric current through wires. If you want electricity to flow, connect the meter to the ground side of the circuit. But if you touch a lead from the meter to the ground by accident, this will make a short in your electrical system and might blow up your fuse or meter.
In this photo, we can see the meter measuring the current on a car. The battery’s positive terminal is connected to one wire attached to the fan. The other wire is attached to a red wire, and then that goes into the meter, and then there’s a black wire that goes into another negative side of the battery. We can’t read what it says on this meter, but it should say about 5 amps or so.
Note that this kind of measurement is usually academic. You don’t often need to measure the current load from one device. When it comes to electric motors, they may have a greater amperage demand as they age, but there’s no way of knowing what an accurate “good” reading is.
Find the Parasitic Drain and Determine What’s Harming the Battery
Current measurement is used to find the source of a parasitic drain. This is something that is not off but should be. You can find it by putting the meter between the negative battery terminal and the car’s body. Then you will know what all of the circuits are doing and how much they are using.
If you want to find a parasitic drain, you can connect the meter. Then pull out fuses until the reading on the meter drops. If you find this, it will show which circuits are connected to that fuse. This is hard to do with modern cars because they have many circuits and fuses.
A problem with modern cars is that it can take a while for the control modules to sleep. You need to switch between high amperage and low amperage to diagnose the drain on your car, but you will break the circuit and reset the timer when you do that.
If you want your car to not start, there is a trick. Purchase and install a battery disconnect switch on the negative battery post. Then:
- You need to set the meter to measure the current at 10 amps.
- Turn the switch so that it connects the battery to the ground. Then electricity can flow.
- Turn off everything in the car, like lights, radio, USB chargers.
- Connect your meter to the battery switch. Connect it between the negative side and the grounding wire. That means that you will need to connect it across a live circuit.
- Turn the switch to disconnect the battery. This will make it so current doesn’t flow through anything. Now, don’t turn on anything that uses electricity. Don’t touch any lights or turn on a fan. If you start your car, there might be too much current, and your meter could break (or at least pop the fuse).
- Read the meter. With everything in your car turned off, the drain should be less than 10A. If it is less than 300 mA, then you can do these things:
- Re-insert the battery and flip the switch to re-energize it.
- You need to set the meter in a “sensitive” setting.
- Re-connect the meter by flipping the switch.
Do not turn off the power. Put it on a more sensitive setting, and the timer will reset automatically.
If you are storing your car, you want to make sure that the current draw is less than 30mA, because otherwise this will drain your battery, or you might end up with an expensive repair bill.
You can buy a current meter. This meter has hinged jaws surrounding the cable whose current you want to measure. The meter then senses the electric field inductively without having to “splice” it into the circuit. Different kinds of meters measure only current or clamps that plug into standard meters.
Clamp meters have a lot of uses. They are best used in A/C wiring. But to use it correctly, you need a low enough accuracy and a high enough price to measure D/C current. You might not want to get this clamp meter if you do not often work with parasitic draw diagnoses.
There is a gray area in the circuit. In a previous post, I explained that there are different types of circuit failures, and one of them is called high resistance failure. To figure out if this type of failure has happened, you need to do a voltage drop test.
Frequently Asked Questions About How To Use a Multimeter: Measuring Current (Amperage)
A multimeter must be inserted into a circuit to measure the current. First, turn the dial to the highest range of current (or 10A if you have a probe in a socket for 10A). If your meter is not auto range, set it to “A” or mA.
The uppercase A symbol is on your multimeter. It is called an amp. There are other symbols too, like milliamps and microamps. Your multimeter probably has a dial that changes the functions from testing AC and DC voltage to continuity and resistance.
To measure AC voltage, you should use the ṽ dial. There are also some DMM’s that have mṽ. First, you should insert the black lead into the COM jack. Next, put the red lead into the VΩ jack. Connect your test leads to the circuit: black first, red second. Read what it says on your display.
A multimeter can be used to measure AC and DC currents. You connect the meter in series with the circuit. That way, when you measure the current in that circuit, it will be limited or controlled by a load or appropriate values of resistance.
How do you calculate amperage? You take the watts and divide them by the volts. For example, if your lights are 60 watts and run on 12 volts, you will get five amps.
Read more: How to Use an Ammeter to Measure Current