Digital Multimeter Safety

October 14th, 2020:
In our previous two technical bulletins, Introduction to Digital Multimeters - Part 1 and Introduction to Digital Multimeters - Part 2 we discussed the different types of multimeters, their basic features and how to make different types of measurements. However, none of this matters if the proper safety precautions are not taken. So here we will discuss digital multimeter (or DMM) safety.

Making measurements safely starts with choosing the proper meter for the application as well as the environment in which the meter will be used. Once the proper meter has been chosen, you should use it by following good and safe measurement procedures. Carefully read the instrument user manual before use, paying particular attention to the WARNING and CAUTION sections.

The International Electrotechnical Commission (or IEC) has established safety standards for working on electrical systems. Make sure you are using a meter that meets the IEC category and voltage rating approved for the environment where the measurement is to be made (check out our article on Electrical Testing & Safety Standards for more information). For instance, if a voltage measurement needs to be made in an electrical panel with 480V, then a meter rated for Category III (or CAT III) 600 V or 1000V should be used.

This means the input circuitry of the meter has been designed to withstand voltage transients commonly found in this environment without harming the user. Choosing a meter with this rating which also has a UL (Underwriters Laboratories), CSA (Canadian Standards Association), VDE (Verband Deutscher Elektrotechniker) or TÜV (Technischer Überwachungsverein or Technical Inspection Association in English) certification means the meter not only has been designed to IEC standards, but has been independently tested and meets those standards as well.

Look for these safety features in a DMM:

  • Independent safety organization approval/listing (UL, CSA, etc.)
  • Fused current inputs
  • Use of high-energy fuses (600 V or more)
  • High-voltage protection in resistance mode (500 V or more)
  • Protection against voltage transients (6 kV or more)
  • Safety-designed test leads with finger guards and shrouded terminals

Common situations that lead to DMM failure:

  • Contact with AC power source while test leads are plugged into current jacks.
  • Contact with AC power source while in resistance mode.
  • Exposure to high voltage transients.
  • Exceeding maximum input limitations (voltage and current)

Types of DMM protection circuits:

  1. Protection with automatic recovery. Some meters have circuitry that detects an overload condition and protects the meter until the condition no longer exists. After the overload is removed, the DMM automatically returns to normal operation. Usually used to protect the ohms function from voltage overloads.
  2. Protection without automatic recovery. Some meters will detect an overload condition and protect the meter, but will not recover until the operator performs an operation on the meter, such as replacing a fuse.

If you missed Part's 1 & 2 on digital multimeters, be sure to check out our
Introduction to Digital Multimeters - Part 1 and Introduction to Digital Multimeters - Part 2

Note: Information taken from an application note courtesy of Fluke Electronics Corporation (which can be found HERE). Ram Meter Inc. sells and stocks an assortment of Fluke digital multimeters and other products, which can all be found on our website at