Multimeters are an important safety device that allows technicians to diagnose problems in all kinds of electrical equipment. However, mistakes made through carelessness or improper training can lead to serious injury or death. While no online article can substitute for a full safety course, this article provides some tips designed to keep you safer while working with a multimeter.
You must always inspect the multimeter before use. If the protective covering on the leads is damaged, don’t use them or try to repair them! Instead, replace them. Damaged protective casings can create situations where you’re exposed to live current. You’ll also want to verify that the multimeter is working correctly against a known source before testing unknown equipment.
While testing any electrical sources, make sure you place test leads far enough apart that they’ll never accidentally touch. If they touch and the current is high enough, they could massively spark, leading to burns or a fire if there is any flammable material around.
Multimeters are certified by a standard known as IEC 1010, which subdivides certified multimeters into four subcategories. CAT I is intended for use with protected electronic equipment with minimal transient overvoltages. CAT II is designed for use with appliances, portable tools, and other household items, as well as outlets at set distances from CAT III and IV sources. CATIII is designed for use with equipment in fixed installations, industrial equipment, feeders and short branch circuits, and the light systems of larger buildings. CAT IV multimeters are designed for working with equipment that connects a building or machine to the electrical grid.
If you’re working with faulty or unknown equipment, there’s a chance that there are large transient spikes. Multimeters under the CAT system come certified for both working Voltage, or the maximum steady voltage at which they can work, and the maximum peak transient impulse they can work with, or random spikes of power.
If it exceeds the limit in the second category, it can burn out the internal fuses, and runs the risk of causing harm. You should also know that while you generally get larger tolerances at higher CAT levels, moving up doesn’t necessarily buy you more tolerance over the previous level. For instance, a CAT III multimeter with 1000 V of working voltage may have a maximum tolerance of 8000 V for transient peak impulses. A CAT IV with 600V of working voltage may also have a maximum tolerance of 8000 V.
If you haven’t yet purchased a multimeter, make sure that you figure out what the absolute worst-case scenario would look like. Then you can determine the highest category you will be working in, and find a multimeter within that category that can handle the voltage of the worst-case scenario.
This is not a complete list that will keep you safe in all circumstances. Multimeters and the associated electrical equipment can cause serious injury or even death. Make sure that you educate yourself on the systems you’ll be working with and on proper, safe use of any tools before you start working with electrical systems.
Hi there! My name is Adam and I write for HealthyHandyman. I have a great passion for writing about everything related to tools, home improvement, and DIY. In my spare time, I'm either fishing, playing the guitar, or spending quality time with my beloved wife. You'll also often find me in my workshop working on some new project!