Fluke - The ABCs of Multimeter Safety: Multimeter Safety and You

Do not neglect safety—your life depends on it.

When safety is at stake, choosing a multimeter is akin to choosing a motorcycle helmet; if you value your head, you will choose a safe helmet. The dangers of motorcycles are obvious, but what about multimeters?
As long as you choose a multimeter with a sufficiently high input voltage, are you not safe? Voltage will always remain voltage, right? Not quite.
Engineers analyzing multimeter safety often find that failing units have been subjected to a much higher voltage than the user thought they were measuring.
Occasionally, accidents occur when a multimeter rated for low voltage (1,000 V or less) is used to measure a medium voltage, such as 4,160 V. In other cases, it was a momentary high voltage spike
or transient that hit the multimeter input without warning.