How To Use a Clamp Meter

How To Use a Clamp Meter

What is a clamp meter?

A clamp meter is basically a multimeter that has a clamp on top. That clamp is used for voltage measuring.

When a user is measuring voltage with a multimeter, he will need to cut the circuit in half to get an accurate reading and make sure that he doesn’t short circuit his multimeter.

Due to safety reasons, a need arose for a tool that will make it possible to measure the voltage on circuits (especially high powered ones) without the need to break them up and risk severe injury or death. That’s precisely what a clamp meter does. It allows the user to put the clamp around the circuit in a parallel position. Because of that, it is not necessary to have any contact with the circuit.

Once we take into account that most clamp meters are fused and CAT certified, we can be sure that voltage measuring has become a lot safer with clamp meters.

What does a clamp meter measure?

A clamp meter can be used to measure all functions that you can measure with an ordinary multimeter, but clamp meters are primarily designed to measure voltage. 

You can measure voltage, amps, continuity, resistance, temperature, and many more functions with a clamp meter.

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Some clamp meters are even outfitted with FLIR cameras, making the temperature probes redundant as you only need to point the camera at an object whose temperature you wish to measure and visually inspect the screen for a result. 

This can save a lot of time for HVAC professionals and car mechanics, as temperature measuring is also an important automotive feature.

How does a clamp-on meter work?

An electric current that flows through the circuit produces a magnetic field. When you take a clamp meter and place it around one wire in a circuit, clamps detect the magnetic field and determine the strength of voltage based on some magnetic field properties.

Since the magnetic field is a byproduct of the current flowing through the wires, the clamp meter can use poles and the size of the magnetic field to determine the voltage more accurately. However, this process has two downsides.

Since the clamp meter needs to convert properties of the magnetic field into a voltage, it is not as accurate as a multimeter. The second downside is the possibility of magnetic interference.

To get an accurate reading as possible, you need to find a wire that doesn’t have two currents running through it because their magnetic fields will cancel each other out and give you a false reading that there is no current in this wire.

How can I check current with clamp meter?

First of all, you need to locate a wire that has only one type of current running through it. When you do that, make sure that you have enough space around the wire so that you can fit clamps around the wire.

After that, take your clamp meter and set it on the voltage setting. Place the clamps around the wire and see what the value of the current is. This was the non-contact voltage testing, a function specific for clamp meters.

It is worth noting that some clamp meters also have the possibility to do this with probes, just like on standard multimeters.

How to use a clamp meter?

Clamp meters can be used to test many things but is always very important to be sure that you are using the correct setting for the task at hand.

The general rule when it comes to using clamp meters is to set the meter on the desired setting, place the clamp around the wire or leads on the poles and read the measurement.

To explain this in more detail, if you are testing for voltage, set the clamp meter to a voltage setting. Spread the clamp around the wire and close the clamp on the wire in between the clamps. Check the reading and make sure that you clamped only one wire.

It is also very common to use AC line splitters in combination with the clamp meter. In that case, it is necessary to plug the AC line splitter in the wall and an object that you want to test in the AC line splitter. 

All that’s left is that you clamp the AC line splitter in a hole that will give you the results that you want.

Clamp meters can also be clamped around the wires. This is very common during the building phase when you want to check to wires, but it is impossible to use the multimeter due to their length.

Many people forget this, but you can use probes with clamp meters. This can be easier in the case that you don’t have enough space around the wire to insert the clamp.

If you are using a clamp meter with a FLIR screen, you will need to set it to a FLIR setting and turn the separate screen on. After that, it is necessary to make sure that there are no other heat sources around the object that you plan on checking for heat because they can change readings for a couple of degrees more or less.

Another thing to pay attention to when using FLIR clamp meters is the distance between you and the object you want to measure. If you are standing too far, you will get a result that shows less heat radiating from an object. 

If you are standing as near as possible to the object that you are testing, the results will be of higher accuracy because there will be less air between the meter and the object.

FLIR clamp meters can be used for DIY, but they are more common in industrial and automotive environments.

Choose an Electrical Conductor to Test

When you are looking for a conductor to test, you need to make sure that you got two things right.

  • Thing number one is the type of currency that flows through the conductor you are going to test, and thing number two is to make sure that you have enough space to place the clamps around the conductor.

Since thing number two is self-explanatory, I’ll now explain the first rule. The currency running through the wire that you are planning to test can’t have both types of currency running through it because you won’t’ get any reading due to magnetic fields canceling themselves out. This can happen if you have a wire with three or four other wires in them.

Clamp the Conductor

To clamp the conductor make sure that you have enough space around the conductor. Open the clamps and place them around the conductor. 

Here’s a mistake that I often see new users doing: When you are placing the clamp around the wire, make sure that you position the wire in the middle, in the hole between the clamps and the multimeter.

New users can sometimes literally clamp the wires between the clamps and then wonder why aren’t they getting a reading.

Once that you have done that it is necessary to keep the clamp meter steady and wait for a few moments to get a reading. It doesn’t matter on what side you turn your clamp meter. As long as you clamp the conductor correctly, you will get a good reading.

If there is no reading and you did everything right, make sure that there is a power running through the wire and also make sure that you have only one type of currency running through the wire.

Use an AC Line Separator

To use an AC line separator you first need to plug the separator in the electric socket and set your clamp meter to the desired setting. 

AC line splitters usually have two holes. The first hole (the hole that is closet to the wall) will give you an exact reading, while the second hole (the hole that is further away from the wall) will give you a reading multiplied by ten. The thing is, if you want a more accurate reading, you will need to use the second hole and then divide the result by ten.

If you need the reading that will be the same as the original one, you need to use the first hole. All that you need to do is to place the clamp on one of the outer edges of the hole that you want to use.

Once again, the direction of the clamp meter is irrelevant since the currency is running through the edges on both sides.

Measure Voltage

It’s the easiest to measure voltage using an AC line splitter. The splitter with separated neutral and live wires on the first part of the wires will work best for this job.

  1. Plug the splitter in the wall and plug the lamp into the splitter. Lamps usually work best for this, but anything small will do.
  2. Take the clamp and set it in the desired setting.
  3. Spread the clamp and insert it around the wire that you want to measure.

All that’s left for you to do is to read the result. A problem can arise if you accidentally clamp both wires, so make sure that you are careful.

One more thing that could happen to beginners is that they become confused and don’t know which wire is the live wire and which one is neutral. If that happens to you all you need to do is check the instructions that came with an AC splitter.

What is a clamp meter good for?

A clamp meter can be good for many things. The number one thing that a clamp meter is most useful for is checking for amperage and voltage. Since most multimeters can measure up to ten amps of current, clamp meters are an excellent choice if you need to measure currents higher than ten amps. 

The thing that makes clamp meters even better is their safety. Since ten amps can easily injure you, clamp meters can make your job a lot safer as they don’t require any contact with the conductor.

Clamp meters can also be very good for automotive and HVAC use.

Basically, if you need to test something and you are wondering if a clamp meter can do it, the answer is simple. Yes, it can. From voltage and continuity to capacitance and temperature, clamp meters can do everything that multimeters can, with only one exception. Clamp meters are safer.

Difference between clamp meter and multimeter

The fundamental difference between a clamp meter and a multimeter is the possibility of noncontact measuring with a clamp meter. Although many other differences exist, another very important difference is accuracy.

Since multimeter probes need to be placed directly in the circuit, the multimeter produces more accurate readings, whereas the clamp meter measures the power of the magnetic field that surrounds the conductor and deduces the power of the circuit from the properties of the magnetic field.

When it comes to noncontact voltage testing, some multimeters have that possibility too. However, clamp meters usually produce more accurate results when it comes to this because it is easier to measure the voltage in a non-contact way with the clamps.

When it comes to size, the difference is obvious. Multimeters can be compact or large, but clamp meters are almost always small. This is due to clamping meters having fewer functions and also because multimeters need more protection.

Most people think that clamp meters can’t use probes, but that is not actually true. Yes, there are some models that can’t use probes, but there are many more that can. When it comes to probes, there is no difference between clamp meters and multimeters.

Clamp meter measurement principles

In order to use a multimeter, you need to interrupt the circuit and place the multimeter probes on the correct poles of the interrupter circuit. 

This process became a problem for technicians because some circuits needed to be replaced after being split in two. These types of circuits are most common in industrial settings, but some can be found in household environments too.

The researchers then started wondering if it was possible to place a device in a parallel position with the circuit to measure various properties of the circuit. And so they came up with a new device called the clamp meter. 

Since clamp meters work in parallel with the circuit, it is not necessary to interrupt the circuit when measuring.

Clamp meters don’t require any contact with the conductor. Instead, they operate by measuring properties of the magnetic field that is produced by the current flowing through the conductor. The clamp meter can deduce the strength of the current by the size and direction of the magnetic field.

Unfortunately, since clamp meters don’t have direct contact with the wires, they are little less accurate than multimeters. However, the decay of accuracy is not a significant one, but a small one.

Types of clamp meters

Clamp meters can be divided by their type of operation and by usage.

Three types of clamp meters according to type exist:

Current transformer (AC), Hall effect (AC and DC) and Flexible (AC) clamp meters.

Current transformer and Hall effect clamp meters work by utilizing their iron cores to capture the magnetic effects of the magnetic field produced by the currency flowing through the wires, while the flexible clamp meters work by utilizing a helix-shaped core that responds to the rate of change of the magnetic field.

Current transformer clamp meters need a lot less currency to be delivered to them to deduce an accurate reading, while the hall effect and flexible clamp meters show less accuracy on less powerful currencies.

The hall effect clamp meter is specific because it has a gap between the clamps. That gap has a hall effect sensor.

When the currency is flowing through the clamp meter, it goes through the Hall effect sensor. The sensor utilizes the gap in which it is located to sense the strength of the magnetic field. Everything else is the same like on the other two clamp meters. Those were the types of clamp meters by their operating principles.

We can divide clamp meters according to their functions, too. Clamp meters are most commonly used by technicians that need to measure various properties of the currency without interrupting the circuit. Some of the most common properties measured are continuity, voltage, amperage, and capacitance.

Clamp meters can also be used for automotive and heating, ventilation, and air conditioning purposes, according to the user’s desire.

Few useful tips while measuring with a clamp meter

New users or people who have worked only with multimeters so far can be a bit nervous when they first start using clamp meters. There is no need for that since clamp meters work in the same way as multimeters do. 

If you get stuck, you can always use the manual that came with your clamp meter, and if that doesn’t help you, Google will.

If you are measuring voltage or amps, and if you need an accurate reading, you can use probes instead of the clamp if your clamp meter supports them.

The probes that work on multimeters work on clamp meters too. My only recommendation when it comes to probes is to pick the best ones possible since clamp meters need accurate probes to give good results.

Although you don’t need to have contact with the conductor while measuring, it would be best if you would wear gloves while doing this, especially if you plan to measure high currencies. 

Anyone who works with electric power knows that a high powered currency has the tendency to ‘jump’ from the conductor towards the technician. More powerful current cam ‘jump’ further away.

!! Remember to use splitters with the clamp meter !!

Not having to isolate conductors will make the job a whole lot more comfortable for you.

If you have pressed the button for spreading the clamps to its maximum and you still can’t spread the clamps enough for them to insert a wide conductor, don’t try to force them because they could break very easily.


This should cover the basics of using a clamp meter. This guide is deliberately not specific because settings and positions of various features may vary from meter to meter.

If you are a new user, make sure that you keep coming back to this guide to remind yourself of important things that you need to have in mind while using clamp meters.

I hope that you will be able to use your clamp meter to its maximum and do a quality job if you are a professional.

If you are using a clamp meter for DIY, I hope that you will have a lot of fun with it.

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