Clamp Meter - measures more than just amperes

There are many different names for the clamp meter:

• Current clamp
• Ampere pliers
• Clamp amperemeter
• Clamp multimeter

To name just a few. But they usually mean the same thing. Classically, you can measure current with a clamp meter. Originally, the clamp meter was a further development of the voltmeter. It was created to enable measurements without having to integrate the measuring device into the circuit in advance, as is the case with the voltmeter or multimeter, for example. In short, its main purpose is the contactless determination of current flows.

However, because you as an electrician not only have to carry out current measurements, but also determine many other variables, the clamp meter  has been extended over time to make it more user-orientated: Today's standard devices have additional measuring leads for determining other variables. These include classic units that are also measured by a multimeter. Namely volts and ohms. There are also devices that can determine other variables such as temperature or capacitance.

So the special pliers for current measurements were gradually developed into a multifunctional measuring device similar to a multimeter. To be precise, the term "clamp multimeter" is probably the most appropriate for this device. However, because it is commonly known as a "clamp meter " or "current measuring clamp", these terms are used below.

Other very specialised clamps, such as leakage clamps, can be distinguished from modern clamp meters. They are not included in the following information.

The multifunctional clamp meter stands out from other multifunctional measuring devices in a number of ways. There are also numerous features that need to be considered when buying one.

Find out more below:

• Structure of a clamp meter
• Measuring with the clamp meter
• Measurement categories
• Advantages of a clamp meter over a multimeter
• Disadvantages of a clamp meter compared to a multimeter
• The clamp meter as a supplementary measuring device
• What you should look out for when buying your clamp meter

How is the clamp meter constructed?

The main components of the clamp meter are the jaw-shaped measuring clamps, which are reminiscent of pliers. You can usually press the jaws open using a lever on the side of the clamp meter housing. The cables or conductors that you want to measure must then be clamped between the jaws.

Under the insulated jaws is a measuring core, usually made of iron or ferrite, which measures the magnetic field that surrounds conductors/cables when they are energised. After determining the electric field, the device indirectly determines the current strength. The measuring core differs depending on the design of the clamp meter . Clamp meters that ONLY measure alternating current do not require any additional components in the measuring core. The current strength can be determined with the help of the alternating magnetic field. If you also want to measure direct current with your clamp meter, you need an all-clamp meter. Direct currents do not generate an alternating magnetic field. It is stationary. For this reason, a small air gap with a so-called Hall sensor is positioned in the measuring core of such all-clamp meters. The sensor ensures that the current strength can ultimately be determined.

Measuring with the clamp meter

The main purpose of the clamp meter was originally to measure current. As mentioned at the beginning, modern devices can perform many more of the following measurements. Your area of application determines which functions you need. In other words, which types of measurement the clamp meter must cover. Within the different types of measurement, the decisive factor is how large the measuring range needs to be. For example, whether you frequently carry out measurements at the lower end of the scale in the micro or milliampere range. Or whether you frequently measure higher currents.

• Electricity
  As briefly summarised above, the clamp meter measures current indirectly via the magnetic field that surrounds electrical conductors. There are two important points that affect the current measurement:

1. The cable or conductor for which the current is being measured must fit through the jaws. The size of the clamp opening is therefore decisive for whether the object to be measured can be measured at all or not. For measurements of large cables, it is therefore necessary to use a clamp meter with a sufficiently large clamp opening. In industrial electrics, a clamp circumference of 30 mm is sufficient.
2. In the lower current range, namely mA or µA, current measuring clamps are often not accurate enough. The lower the current, the lower the magnetic field surrounding the conductor/cable. In addition, external influences then particularly disturb the already low magnetic field. As a result, many (cheap) clamps that do not have a low-pass filter can no longer reliably detect small currents. You can read more about this below in the chapter "What you should look out for when buying your clamp meter."

Most pliers available on the market are suitable for DIY measurements. There is virtually no need to measure small currents in the micro-ampere range at home. However, the clamp meter is a device that is intended for professional use. For home use, the devices are usually equipped with an unnecessarily large number of functions and are therefore too expensive.

• Tension
  A measuring range of up to 600V AC/DC is sufficient for DIY and home use. In a professional environment, it should be at least 1000V AC/DC. Especially if you are installing photovoltaic systems or working in the field of e-mobility. To ensure that you are adequately equipped for these future technologies, you should even be able to measure a measuring range of up to 1500V for the DC side. The Wiha clamp meter already covers this requirement today!

• Resistance
  Look out for high-resistance devices if you frequently work on solar and photovoltaic systems, in the field of electromobility or in the plumbing and heating sector. Measurements in the kilo ohm range should then be mandatory. Inexpensive clamp meters already cover the measuring range of the ohm unit for home use.

• Frequency, temperature, capacitance and other measurement types
  Some clamp meters also have other types of measurement. These are generally only really necessary for professional use. The area of application and the associated measuring range are also decisive for the purchase.

Measurement categories

Like all test devices, the clamp meter is divided into four different measurement categories. The measurement category provides information on the application and the voltage under which the clamp meter may be used.

You can find more information about the measurement categories in our multimeter category:

To the multimeter category

Advantages of a clamp meter over a multimeter

Advantage 1:
When measuring with a multimeter, the measuring probes usually have to be integrated into the measuring circuit. This means you have to break the measuring circuit, which is time-consuming and also poses a safety risk because the circuit is exposed. On the other hand, you can take measurements with a clamp meter without having to break the measuring circuit. You can therefore measure faster, more conveniently and also more safely because the circuit remains closed.

Advantage 2:
Advantage 1 means that you can also use the clamp meter to take measurements during operation. In addition to the faster measurement, this also has the advantage that machines do not have to be stopped and production processes, for example, can continue undisturbed. This is therefore particularly advantageous for industrial electricians.

Advantage 3:
While most multimeters can measure currents of up to 10 or a maximum of 20 amps, a clamp meter can measure between 400 and 600 amps. For very specialised applications where even higher amperage values need to be determined, you will need to use very special clamp meters.

Disadvantages of a clamp meter compared to a multimeter

The clamp meter is particularly suitable for measuring high currents. The indirect determination of the current value has the following disadvantage: For measurements of current values in the micro or milliampere range, inexpensive models in particular are very inaccurate. And therefore often unusable. So if you need a clamp meter that also measures amperes in the micro range, you will have to reckon with a higher purchase price. Technologies such as a low-pass filter, which filters out interference signals so that small currents can be measured precisely, have their price.

The clamp meter  as a supplementary measuring device

When troubleshooting electrical systems, voltage and current often have to be measured simultaneously. Regardless of which measuring device you are using, only one measurement can usually be carried out at a time. Unless you have a device with several measuring channels. For cost reasons, most electricians do not have such a device. It therefore makes sense to have another device for measuring currents in addition to the device that measures the voltage. This allows you to take two measurements at the same time.

Note:

In Germany, Austria, Switzerland and some other countries, only a two-pole voltage tester is authorised to determine the absence of voltage in accordance with DIN EN 61243-3 VDE 0682-401. All information on this tester can be found on the "two-pole voltage tester" category page.

To the voltage and continuity testers (two-pole)

What you should look out for when buying your clamp meter

1. Application, measuring range and measuring category
   The most important factor is certainly your intended use and which measuring range you require. The respective measurement categories must also be taken into account. Pay particular attention to the lower end of the measuring scale if you often need to measure very low currents.

2. Size of the jaws
   Before purchasing, think about the main size of the cables you need to measure. Otherwise, it may not be possible to grip the test object with the pliers.

3. Multifunctional measuring
   Do you often need to measure other electrical values in addition to amperes, such as voltage, resistance, capacitance, etc.? Then make sure that your clamp meter offers classic multimeter functions. This means that you may not need any other measuring devices. It often makes sense to use the clamp meter for parallel measurements in addition to a voltage tester or a multimeter.

4. LPF: Low pass filter
   An LPF low-pass filter is useful. This enables precise measurement results, especially in the low ampere range, because the filter eliminates interference signals.

5. TRUE-RMS measurement
   If clamp meters have a TRUE-RMS function, the device measures more accurately if the sinusoidal shape of an alternating current deviates from the ideal, i.e. if it is distorted, does not correspond to the typical sinusoidal curve or is distorted. The measurement results are therefore more meaningful and correct than with devices that only use an RMS function. The TRUE-RMS function is also abbreviated to TRMS. It is important for all specialists in industrial electrics.

6. Display
   Illuminated LCD displays are particularly useful when measuring in poor lighting conditions. This means you can always read the result easily.

7. Torch function
   Also very convenient for working in poorly lit environments.

8. Data Hold Funktion
   The data hold function saves measured values on the device. This is particularly useful if the measured value cannot be read directly because you are measuring in confined spaces. In addition, you can often compare the saved values with other measured values.