Oct 45 min read

How to Measure Current With a Multimeter

Follow Along on SkillCat: "Using a Multimeter" Course!

In this multimeter use guide, learn about how to use a clamp and digital multimeter for current measurement.

Want to test your knowledge? Skip to the quiz!

Things to Keep in Mind:

There are two types of multimeters: clamp multimeters and digital multimeters.
Multimeters can be used to measure various measurements:
- Measure voltage in Volts
- Measure current in Amperes - this if the focus of this guide!
- Measure resistance in Ohms
- Measure continuity in Ohms
- Measure capacitance in Farads
- Measure temperature in Farenheit or Celcius
Safety must be a priority when measuring current!

1. An Overview on Current

Current can be defined as the rate at which electrons flow within a circuit. The unit of measurement for current is amperes, or amps (A). There are two types of current, alternating current (AC) and direct current (DC). In alternating current, the direction of flow alternates direction, while direct current only flows in one direction. While you can use an ammeter for current measurements, this guide covers how to safely take measurements of both AC and DC current using clamp multimeters or digital multimeters.

2. Measuring Current

Before measuring current, it is important to keep in mind that current is incredibly dangerous and can kill you. Touching a high current wire can be like getting struck by a lightning bolt. Proceed with extreme caution when handling live wires or taking current measurements.

Since amperes (A) is the unit of measurement for current, look at the “A” port on your multimeter before taking any current readings. The number next to the “A” is the maximum current your multimeter can handle. Do not measure any current that will exceed this limit.

There are two main tools for current measurement:

Clamp multimeter
Digital multimeter

Measuring Current Using a Clamp Multimeter

clamp multimeter taking measurements of current

A clamp multimeter is the simplest and safest way to measure current, as it doesn't require you to touch any wires. This significantly reduces chances for an injury. With clamp multimeters, you do not need test leads. Let’s start by learning how to set your multimeter dial for current measurement.

The schematic diagrams for equipment typically indicate if a system is AC or DC. If you are measuring AC current, point the dial towards the “A” with a wave over the top. If you are measuring DC current, point the dial towards the “A” with a straight and dashed line on top. You may need to press the yellow function key to set the meter to AC or DC.

Press the button on the left hand side of the multimeter to open the clamp jaws. Move the multimeter so that one wire is inside the clamp - then release the button so that the jaws close. Do not touch the wire during this process, be sure to only move the multimeter.

Once the wire is inside of your closed meter, position the wire in the center of the clamp. The wire should not be touching any surrounding edges of the clamp or the multimeter. Read the current measurement and unit on the multimeter’s display.

The term live wire refers to a wire with power running through it. When you are using a clamp meter, do not touch the wire you are testing. The farther your hand is from the live wire, the safer you are. For safety, your hand should be on the bottom half of the meter.

Measuring Current Using a Digital Multimeter

Next, you will learn how to measure current with a digital multimeter. Measuring current with a digital multimeter can be very dangerous. Always treat wires as if they have power and proceed with caution.

To measure current, you will need to connect your test leads into the correct ports on your multimeter. The red lead plugs into the “A” port. The black lead plugs into the “COM” port.

When measuring current, you should always start with the red lead in the "A" port. Some multimeters will have a port for measuring small amounts of current, labeled “mA”. For very small amounts of current, your red lead can plug into your “mA” port. However, do not use the "mA" port until you have tested and confirmed that the current is small, as you risk injury using the port on large amounts of current.

If you are measuring AC current, point dial towards the “A” with a wave over the top. If you are measuring DC current, point the dial towards the “A” with a straight and dashed line on top.

To measure current, you must connect your test leads in series with the circuit. Series circuits only have one path for the current to flow, and current moves from one component to the next.

First, you will have to disconnect the circuit. This step can be extremely dangerous. If possible, use a clamp multimeter instead of a digital multimeter, as clamp multimeters does not require you to disconnect a circuit. Turn off the power to the circuit. Once the power is off, continue to act as if the circuit has power. Test to confirm that the circuit is de-energized by testing the voltage of the circuit. If there is no voltage in the circuit, then you can continue.

digital multimeter measuring current of 0.79 amperes

Disconnect the wire leading into the component you are measuring. There should be an open gap in the circuit now. Press one test lead to the end of the disconnected wire. The other test lead should be pressed into where the wire would connect into the component.

Turn the circuit's power back on once you have safely connected your multimeter in series. Do not touch any live wires or you can be fatally injured. Hold your test leads as far from the metal tips as possible while maintaining control.

The current should be reading on your multimeter display. The units of amperes will be shown on the multimeter display as well.

Quiz

Now that you know how to measure current using a clamp and digital multimeter, test your knowledge with a quick quiz!

Question #1: Current can easily kill you if you are not careful.

True
False