Sparky Guide: 5 Things to Look for When Selecting a Multimeter

Whether you're a sparky tackling a new residential installation, a compliance officer ensuring safety on a commercial job site, or an industrial electrical technician troubleshooting intricate machinery, the right test equipment is critical. With the right digital multimeter (DMM) for the job, you can reduce fault-finding time, minimise errors and address complex electrical challenges with confidence.

Multimeters are rated for safety using a category system as per IEC 61010-1 (CAT ratings). The CAT rating, combined with the rated working voltage, helps you understand what electrical environment the meter is safe to operate in. Here is a basic overview:

• CAT I: For low-energy equipment not directly connected to mains (e.g. small electronic devices)
• CAT II: For measurements performed on circuits directly connected to the low voltage installation (e.g., household appliances)
• CAT III: For measurements performed in the building installation (e.g. distribution boards or circuit breakers)
• CAT IV: For measurements at the source of the low-voltage installation (e.g., mains service or utility connection).
  

Put safety first and choose a tool with a CAT rating and rated operating voltage that is suitable for the task at hand and never use a meter to perform a higher category measurement than it is rated for. Most professional electricians would typically have a CAT III or CAT IV rated multimeter in their kit.

Tip: CAT ratings also apply to the test leads used with your multimeter, so don’t forget to make sure you’re using suitable leads.

As the name suggests, a digital multimeter helps a sparky perform multiple different electrical tests. This could include accurately identifying voltage drops indicative of high resistance joints or undersized conductors, precisely measuring current draw to assess load and potential overloads and reliably checking resistance values to diagnose component failures or confirm circuit continuity. These functionalities directly contribute to reduced fault-finding time, minimised errors, and ultimately, safer and more compliant work practices.

Electricians in Australia and New Zealand must adhere to the AS/NZS 3000 Wiring Rules, which include tests for continuity, polarity, insulation resistance, and loop impedance, among others. A good multimeter should be able to handle:

• AC/DC voltage
• AC/DC current
• Resistance
• Continuity with audible buzzer
• Diode testing

Advanced models may also include functions for temperature, capacitance, frequency, and more. The ability to measure frequency is invaluable when analysing motor drives and power quality issues, while capacitance testing aids in evaluating the condition of capacitors within various electronic systems.

So, when you’re choosing a digital multimeter, it’s important to think about the electrical testing you perform daily and what features will be most beneficial for you. Whether you’re verifying mains supply integrity, diagnosing cable faults, confirming correct equipment operation, or ensuring the safety of electrical installations in accordance with AS/NZS 3000, make sure your meter covers the required tests for your typical work.

Accuracy matters, especially when you're performing detailed diagnostics or certifying work. Look for a multimeter that provides true RMS readings, which provide more accurate measurements on non-sinusoidal waveforms often found in modern electrical systems.

Check the specification sheet for:

• Voltage range
• Current range
• Basic DC accuracy (expressed as a percentage, e.g., ±0.5%)
  

We’re not here to give a physics lesson, so let’s keep this really simple. When you’re using a multimeter or clamp meter to measure AC volts or amps, True RMS (True Root Mean Square) means you get a more accurate reading, regardless of what the waveform looks like.

Basic meters without True RMS assume the power is a nice clean sine wave. They’ll give you decent readings in that case. If it’s not a pure sine wave and your meter isn’t True RMS, it could give you a reading that’s way off.

A True RMS meter takes a proper average of the signal, no matter how ugly it is, and gives you the real value. If you’re working with modern gear, it’s probably best to save second guessing and get yourself a True RMS meter.

Durability is crucial in a tool that's going to be tossed into your tool bag and used on construction sites. Look for features such as:

• Rugged, rubberised casing
• Impact resistance

Then there are the features that don’t directly relate to the measuring capability but are instead designed to make life easier for you. For instance, you may want to invest in a device that not only provides accurate readings but also incorporates features that streamline testing procedures, such as:

• A data hold to freeze critical measurements on the display or relative mode for comparative analysis.
• A Beep-Jack input warning, which can prevent accidental misconnections, providing an extra layer of protection for the user and the equipment.

These practical enhancements can significantly improve productivity and diagnostic capabilities, allowing you to concentrate on billable jobs effectively.

A digital multimeter is one of the bigger ticket items in your kit, and not something you’ll want to replace every year. A long warranty is often a good sign that the manufacturer is confident that their meter will survive out in the field. Look for multimeters that come with at least a 2 to 3-year warranty and check if the manufacturer offers spare parts or repairs. Some of the best leading brands offer extended warranties for additional peace of mind.

Ultimately, selecting the appropriate digital multimeter is a strategic investment in professional competency and the quality of workmanship, crucial for a wide range of applications from residential and commercial electrical installations to demanding industrial and mining environments.

When it comes to combining performance, accuracy and durability, the BM822 Professional Digital Multimeter stands out as a top choice for electricians. While it’s specifically engineered for robust performance in challenging settings such as heavy industry and mining, the BM822 is a reliable workhorse for everyday electrical tasks. Its true-RMS measuring capability, CAT IV rating, and industry-leading warranty make it a trusted and popular multimeter for electrical professionals across all sectors of the industry. Known for its rugged construction, this meter provides all the fundamental features a professional tradesperson requires in a DMM.

• CABAC Professional True RMS Digital Multimeter Item Number: BM827 Packaging Unit: 1 / each View Product
• CABAC High Performance Professional Digital Multimeter Item Number: BM869 Packaging Unit: 1 / each View Product
• CABAC Professional Digital Multimeter & Data Logger Item Number: BM525 Packaging Unit: 1 / each View Product
• CABAC General Purpose Digital Multi Meter Item Number: BM251 Packaging Unit: 1 / each View Product