Multimeter buying guide

Multimeters are test tools designed to measure different electrical values. The main role of a multimeter is to protect you against the risks of electric shocks or, worse still, electrocution. They do this by checking the voltage of live wires. Voltage is indicated in volts (V). All multimeters can be used as voltmeters to perform this function. This highly useful feature allows you to detect faults, failures or anomalies in an electrical circuit.

Most multimeters are also able to work as ohmmeters to test continuity. This function is used to test resistance in ohms (Ω) between two points in a circuit. Typically, the multimeter emits a beep when it is in its lowest resistance limit meaning there is continuity. Most modern multimeters feature a wide range of additional features to measure things like current, impedance, capacitance (by charging capacitors) and even wattage (with a clamp meter). While most multimeters look very similar, take special care to study all the different measuring modes on offer as this factor will play a big part in the versatility and price of the device.

1. Analogue multimeters

Analogue multimeters are easy to spot as they feature a needle meter. Value readings are displayed on the analogue needle-pointer scales according to the setting you have selected. Contrary to what you might expect, this technology is accurate and reliable, and has proven its worth over decades of use.

2. Digital multimeters

Rather than the analogue panel meter, digital multimeters are equipped with a numeric screen where readings are displayed directly. An analogue to digital converter is used to make it easier to select different settings and take readings. Easy to use, waterproof and impact-resistant, digital multimeters are also now available at affordable prices and are gradually replacing analogue multimeters.

A DIYer won't have the same requirements in terms of settings, display and accuracy as a professional tradesperson. Let's take a quick look at the most useful features to seek out, depending on your needs.

Multimeters for occasional DIY jobs

An entry-level multimeter will largely suffice for jobs like testing light bulbs, wiring sockets, testing batteries or measuring voltage at a consumer unit. Voltmeter and ohmmeter modes will allow you to tackle a range of tasks by ensuring the presence or absence of electrical voltage. Go for a device with a large voltage testing range (200 mV to 200 V DC voltage and 0 to 600 V AC voltage) to cover all bases. The ohmmeter mode should cover a resistance range of 0 (continuity test) to 2 megaohm (M Ω). Whether you go for a digital or analogue multimeter, choose a device with a limited ranges to prevent errors and ensure the device is easy to use.

Multimeters for regular use

Find yourself needing to test electrical installations or circuits on a regular basis? Do you work on circuit boards or electrical equipment? Need to be able to detect basic faults? All of these situations call for the use of a slightly more sophisticated and reliable multimeter with a range of additional modes. Look for a multimeter that can measure current (in amps or A) as well as resistance and voltage. A 'fork clamp' multimeter is a great option as it allows you to take measurements without having to disconnect wires or interfere with the electrical installation in any way. Basic ranges (10A DC and 200A AC) should cover your needs. A digital multimeter will make it easier to take measurements and read values.

Multimeters for frequent or trade use

Are you a tradesperson or do you have a solid foundation in electrical work? Know your electrical installations in and out? Do you work with industrial-scale voltage (over 230 V and/or three phase power) and regularly troubleshoot electrical equipment and machines? If so, you are going to need a top-of-the-range multimeter with all the operating modes you need and the right kind of measuring range for your tasks. When it comes to measuring voltage, choose a model that can cover up to 200 V DC and 1000 V AC. In terms of current, go for a multimeter that can measure up to 10 A DC and 400 A AC. For troubleshooting tasks, a multimeter that can measure the capacitance value of a capacitor (in farads or F), impedance (in ohms or Ω) and power (in watts or W) will be very helpful. A digital multimeter is a must-have for professional use.

If the time has come to choose a multimeter and you're still stuck between a few different models, here are a few criteria to help you out.

1. Accuracy

Accuracy basically refers to the difference between the actual value and the value indicated by the device. The smaller the difference, the more accurate the device.

2. Resolution

Resolution is the smallest increment a tool can detect and display. The smaller the increment, the more accurate the measurement.

3. Effective value

Multimeters can be:

• RMS (Root Mean Square): ideal for DC voltage;

• or TRMS (True RMS) for AC voltage.

4. Protection

This refers to the type of input protection which is generally provided by one or several fuses. Some more sophisticated models also have reverse polarity protection and/or overload protection.

5. Multimeter standards

All multimeters need to meet the requirements set out by the standard IEC 601010. This standard splits devices into four categories depending on its intended use and specified measurement range:

• category III: distribution level mains; fixed installation.

• category IV: primary supply, overhead or underground utility service.

• category I: signal level, special equipment or parts of equipment, telecommunication and electronics.

• category II: local level mains, appliances, portable equipment.

Above all, remember that electricity is dangerous – it can cause shocks, burns and can lead to death. You cannot avoid accidents simply by purchasing a high-quality measuring device. Be sure to use best practices at all times and take care to check that your device is set to the correct mode. Take special care of the test probes. The wires must be kept dry and clean at all times and the wires must never be stripped or damaged in any way. Finally, never overestimate your own abilities. Owning an electrical tool does not make you an electrician!