Which clamp meter to buy?

29 Apr.,2024

 

Which clamp meter to buy?



Generally for most electricians work (leaving aside R&D labs, etc, where anything is possible) you would be looking at two uses:
  • Current consumption (clamp on only L, or only N)
  • Earth leakage (clamp on both L & N to see residue)
For current consumption you are probably worried about if a load is close to (or above) the MCB or switch rating so probably you would be looking at 1-100A in a domestic situation and normally you would want to be able to see a bit above the expected range, so going to 200A is a reasonable upper limit here.

For earth leakage you are going to see RCD that are mostly rated at 30mA, a few incomer that are 100mA, and a few special area that are 10mA. So when testing at the cables to the appliance or RCD/RCBO you would want to measure down to 1mA with decent accuracy.

Most digital meters have a combination of % and digits as the "accuracy" so in my DiLOG meter's case it says the lowest range is 200mA, resolution 0.1mA, and accuracy 2.5% + 8 digit. So for very low currents it is possibly 0.8mA out, but for something like 10mA it would be 10 * 2.5% + 0.8 = +/-1.1mA max error. That is still adequate to check if a circuit is close to the trip threshold for practical RCD cases.

Some boast lower settings so you can measure appliance leakage at low levels, as if doing a PAT test, but that is an unusual approach as if you are needing to do PAT testing it is far better to get a proper tester for that role, such as this sort of thing:

Seaward Primetest 100 PAT Tester

The Battery powered Seaward Primetest 100 PAT Tester is a quick and easy to use PAT tester. The Primetest 100 gives readings as well as PASS & FAIL readouts, ideal for the novice user.

If you are looking for more details, kindly visit our website.

The Megger is DMC305e is a better specification than the DiLOG DL6518E (or the even cheaper TEK775 that looks identical) but also costs more, so you need to ask yourself if it is money well spent?Generally for most electricians work (leaving aside R&D labs, etc, where anything is possible) you would be looking at two uses:For current consumption you are probably worried about if a load is close to (or above) the MCB or switch rating so probably you would be looking at 1-100A in a domestic situation and normally you would want to be able to see a bit above the expected range, so going to 200A is a reasonable upper limit here.For earth leakage you are going to see RCD that are mostly rated at 30mA, a few incomer that are 100mA, and a few special area that are 10mA. So when testing at the cables to the appliance or RCD/RCBO you would want to measure down to 1mA with decent accuracy.Most digital meters have a combination of % and digits as the "accuracy" so in my DiLOG meter's case it says the lowest range is 200mA, resolution 0.1mA, and accuracy 2.5% + 8 digit. So for very low currents it is possibly 0.8mA out, but for something like 10mA it would be 10 * 2.5% + 0.8 = +/-1.1mA max error. That is still adequate to check if a circuit is close to the trip threshold for practical RCD cases.Some boast lower settings so you can measure appliance leakage at low levels, as if doing a PAT test, but that is an unusual approach as if you are needing to do PAT testing it is far better to get a proper tester for that role, such as this sort of thing:

How to Use Clamp Meters

Ready to learn? Tips for using clamp meters, related precautions, and more

Overview

To measure parameters like current and voltage, you’ll need a dedicated instrument. Instruments such as analog multimeters and digital multimeters are often used to measure current, but they require that the circuit be cut so that the instrument’s test leads can be inserted into the circuit in series. In many cases, it’s not possible or practical to do that. Cutting the circuit also poses risks, for example of electric shock.

Clamp meters are a convenient choice in such situations. This page offers a detailed explanation of how to use a clamp meter as well as related precautions.

What is a clamp meter?

A clamp meter is a clothespin-shaped instrument that can be clamped around a live wire in order to measure the current it’s carrying. As a measurement principle, clamp meters detect the magnetic field emitted by current flowing in a wire in order to measure the current value.

Unlike instruments like multimeters, this design has the advantage of being able to measure current without requiring that the circuit under measurement be cut. Broadly speaking, there are two types of clamp meter:

  • Models designed to measure load current
  • Models designed to measure leakage current

Instruments can be further classified based on other differences, for example whether they measure direct current (DC) or alternating current (AC), and whether they use mean value rectification or the RMS method. Load current models are used to measure normal AC circuits. Some recent clamp meter models can measure both load current and leakage current.

Basic method for using a clamp meter

This section provides an easy-to-understand introduction to using load current and leakage current clamp meters.

Information that applies to both types

Generally speaking, load current and leakage current clamp meters are used in the same basic manner. First, if your clamp meter allows you to choose DC or AC current, choose the type of current that’s appropriate for the circuit you wish to measure. Then set the measurement range based on the magnitude of the current you’ll be measuring. If measuring a DC current, don't forget to perform zero-adjustment.

Once you’re ready, open the clamp meter’s jaws and clamp them around the wire you wish to measure. Position the wire in the center of the clamp for maximum measurement accuracy.

Using a load current clamp meter

Clamp meters designed to measure load currents can only be clamped around one wire. Be careful not to clamp the instrument around multiple wires at the same time as doing so will prevent proper measurement.

Using a leakage current clamp meter

Clamp meters designed to measure leakage currents require a bit more caution. Ground wires should be measured alone. If measuring an AC circuit, clamp the instrument around all the wires (two if single-phase; three if three-phase).

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When measuring leakage current, two wires may be clamped simultaneously.

Leakage current is a current that flows to the ground through the insulation resistance of the load, and can be several tens of μA if many loads are connected. By using a clamp meter, the minute difference flowing in both directions can be detected and identified as leakage current.

Things to avoid

As with analog multimeters and digital multimeters, there are a number of precautions that should be borne in mind when using a clamp meter. For example, if you leave a clamp-on power meter connected after use, an excessively large current flowing to the clamp sensor could damage the instrument.

Additionally, avoid clamping an instrument to a bare conductor; clamp meters should only be used to measure insulated conductors (although this depends on the specific current sensor in use).

Clamp meters offer a high level of safety since they don't require the wire under measurement to be cut, but it’s important to use them at or under the maximum rated terminal-to-ground voltage. Finally, the instrument's barrier indicates the safety limit, so never touch anything on the jaw side of the barrier while using the instrument.

Choosing the best clamp meter

As described above, clamp meters are available in a variety of models that are designed for different applications, for example depending on whether they’re engineered to measure DC or AC current. Consequently, it’s necessary to choose an instrument based on your intended application. For example, in order to measure a battery used in an automobile or uninterruptible power supply (UPS), or a photovoltaic cell, you’ll need a clamp meter that can measure DC current.

On the other hand, if you wish to measure load current or leakage current in an AC circuit such as lighting or power lines in a home, building, or plant, you’ll need an AC clamp meter. Choose an AC load current clamp meter for ordinary measurement applications, or a leakage current clamp meter if you need to measure leakage currents caused by insulation defects or current flowing in a ground wire for electrical equipment.

Using clamp meters safely

Clamp meters are convenient instruments that can measure current and other parameters simply by being clamped around a wire, which doesn’t need to be cut. They’re easy to use safely since doing so requires only that the instrument be clamped around a wire. However, these instruments can be dangerous if used improperly. Consequently, be sure to refer to this article’s instructions and precautions related to choosing and using clamp meters to ensure safe use.

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Contact us to discuss your requirements of leakage current clamp meters contractor. Our experienced sales team can help you identify the options that best suit your needs.

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