Best Clamp Meters

Buying guide for Best clamp meters

A clamp meter allows you to accurately measure live current without shutting off the electrical system. You can test for resistance and frequency, among other things, and many clamp meters also test for temperature. The two main groups of people who use clamp meters are professional electricians and DIY home enthusiasts who need to test live electrical circuits. In these situations, a clamp meter is indispensable.

Which kind of clamp meter should you get? There are numerous brands on the market with different features, so it can become a little confusing even for a professional. We’re here to help simplify things for you. 

Clamp meters are valuable because they can measure current without the system being off.

Key considerations

Multimeter vs. multi-tester

A quick note about terminology. The terms multimeter, or meter, and multi-tester, or tester, are often used interchangeably, but some manufacturers argue that a tester is only used to confirm the presence or absence of an electrical signal whereas a meter is used to measure the strength of the electrical signal. There’s no universally agreed upon answer, and we’re not going to try to settle the issue, but for our purposes here we’ll use the terms multimeter and clamp meter.

Safety

Safety comes first in all things, and this is particularly true when dealing with electricity. If you’ve ever been shocked by a live wire, you know it doesn’t take much to turn a mild shock into a life-threatening situation. The UL 61010-1 standard is a safety standard for the manufacture and use of devices that measure, test, indicate, or record one or more electrical (and some physical) quantities.

Clamp meters that don’t meet the UL 61010-1 standard should be regarded as potentially dangerous. They might work, but if they don’t meet the safety standards, they may not be safe, properly grounded, shielded, or protected.

Also, know what kinds of electrical equipment you’re going to be testing. If the maximum current is 600 amps or more and you get a 500-amp clamp meter, you’re not only putting the meter at risk, you’re also taking a chance on giving yourself a shock.

True RMS

A good clamp meter needs to be precise and accurate. That means it needs to give true RMS readings. Root mean square (RMS) is a mathematical term that refers to the effective level of an electrical current. Direct current (DC) is exactly what the name suggests: direct, unwavering current coming from a source. Alternating current (AC) is composed of alternating high and low voltage in a sine waveform.

While some multimeters simply measure the average of the highs and lows of AC power, a true RMS meter provides accurate readings for the correct current level or voltage. Most meters today are true RMS meters, but if you find one that isn’t, be aware that it will only provide averages and not exact readings.

Durability

Electricians often work in tight spaces, hot attics, or freezing conditions, in all types of weather. Make sure your clamp meter is appropriate for the environment you’re going to be working in and can take the extremes without losing accuracy. Also, during normal use, the clamp meter will inevitably be struck, knocked over, or slip out of your hands. A good clamp meter should be able to survive physical abuse, shocks, and drops.

Features

People have grown accustomed to associating many features with quality. That may be true in some cases, but not with clamp meters. It’s better to have fewer features that work correctly every time than a plethora of features you don’t need.

Here are the features we think are essential. Anything beyond this is up to you and your requirements.

Accuracy

Current transformer clamp meters only measure AC current. This is the original type of clamp meter.

Hall Effect clamp meters can measure both AC and DC currents. Most modern clamp meters are Hall Effect clamp meters. A clamp meter can be a Hall Effect clamp meter without being a true RMS clamp meter.

Electrical limit

Any clamp meter that measures 400 amps or less may be too limiting for professional applications. Most clamp meters measure 600 amps, and some go as high as 1,000 amps. Make sure the clamp meter you get is appropriate for what you’ll be measuring.

Backlit screen

You can encounter dim or low-light conditions when working in electrical closets, under buildings, behind appliances, and in other enclosed spaces. In those conditions, you’ll be grateful your clamp meter has a backlit screen so you can see the readings.

Controls

Labels: Clear labels, written in high-contrast colors, are another necessary feature of a good clamp meter. Too small or too low-contrast lettering will be hard to read and could lead to using the wrong settings, setting up a potentially dangerous situation. The controls associated with those labels should be large, tactile, and easy to grasp. They should be coated with nonslip material so you can get a good grip on them in cold or damp conditions.

Hold button: A hold button is a helpful feature that lets you “freeze” the readings so you can record them. If you need to write down the readings for later use, a hold button is an indispensable feature.

Clamp meter prices

Inexpensive

The low price range for clamp meters is anything under $20. These multimeters have very few features like hold buttons, and the labels aren’t always clear or easy to read in low-light conditions.

Mid-range

The medium price range for clamp meters is from $20 to $100. There is a vast array of features available in this range, along with good warranties from top manufacturers. These meters are more reliable than cheaper ones.

Expensive

Professional clamp meters cost $100 and more. Some that cost over $200 have detachable clamps on a cable for reaching into tight spots while keeping the main body of the meter where you can read it.

Tips

• Take multiple readings. You should take multiple readings several minutes apart when measuring live current. This will give you a better picture of the true level of the current.
• NEVER use the clamp and probe wires at the same time.
• Keep your fingers and hand behind the ridge or hilt when measuring with the jaws.

Even though clamp meters are heavily insulated, it never hurts to wear insulated gloves when you’re working in a high-energy environment.

FAQ

Q. How much current does a clamp meter actually detect when it’s used?

A. It typically only detects about 1/1000th of the actual current flowing through the conducting wire or cable. So, if it detects 3 milliamps, it multiplies that by 1,000 and displays 3 amps on the readout.

Q. What electrical/physical quantities can a clamp meter measure?

A. Capacitance, frequency, phase (waveforms), resistance, and temperature.

Q. What’s the difference between a clamp meter and a digital multimeter?

A. A clamp meter measures current and can go as high as 1,000 amps. A digital multimeter measures voltage and tops out at around 10 amps.