Clamp meters are crucial electrical testing tools. You’ll find them in any electricians’ or control technicians’ toolkit, allowing workers to test circuits with greater precision and in a safer manner than ever before.

There’s no need to cut through wires, insert test leads, and take inline measurements with clamp meters. Instead, you can take the measurement without ever needing to touch a conductor.

You’ll find electricians using new clamp meters for various applications, such as when working with industrial or commercial HVAC systems, industrial controls and equipment, and electrical systems.

If you’re wondering how clamp meters work, this article will tell you everything you need to know.

What does a clamp meter measure?

Essentially, clamp meters are electrical meters with integrated AC clamps. They’re also known as clamp-on ammeters, amp clamps, and tong testers.

Clamp meters, in short, measure the vector sum of all currents flowing through conductors as they pass through a probe. Electricians can use this tool to analyze live conductors without needing to interrupt the circuit.

Many modern clamp meters, however, function more like digital multimeters. These devices often also include ohmmeters, voltmeters, and other measurement tools, making it possible to measure resistance, continuity, and voltage.

How do clamp meters take measurements?

Clamp meters take measurements thanks to a principle known as magnetic induction. Magnetic induction describes a process in which a changing magnetic flux produces voltage or current within a conductor.

Clamp meters contain current transformers. As electric current moves through a wire, it creates a magnetic field. These transformers sense fluctuations in the magnetic field, converting the value to an AC reading. The meter’s digital screen will then display this reading.

As such, clamp meters are an excellent choice for measuring high AC currents.

Because direct current flows in a fixed polarity, the conductor’s magnetic field will not change, preventing traditional clamp meters from taking a reading. Instead, you’ll need to use a DC clamp meter, which uses the Hall effect.

A Hall effect sensor detects the magnetic field produced by current flow, causing a small, measurable voltage across the sensor. This voltage is proportional to the current, allowing the clamp meter to amplify and measure it.

What are the benefits of using a clamp meter?

Clamp meters are safer and much more efficient for taking current measurements when compared with traditional tools. You can use them to take measurements and repair systems on an as-needed basis—there’s no need to shut off circuits beforehand.

These multifaceted tools are also great for troubleshooting installation issues, supervising apprentice electricians installing equipment, and performing final tests on a circuit.

Finally, you can use clamp meters for performing general system troubleshooting and scheduled maintenance.


To summarise, clamp meters measure current as it flows through a circuit—although some varieties can also measure voltage, continuity, and resistance.

Unlike traditional current measurement tools, clamp meters do not need to contact a conductor to take the measurement. You don’t need to turn off the circuit before you start measuring, so they’re a much safer, more efficient option.