Use the OEM-recommended fuse as identified in the meter’s manual. There is zero room for negotiation and no exceptions.
The fuse is a critical safety element for your multimeter. This matters for industrial technicians working in 208 and 460 VAC service panels as an incorrect fuse defeats the meter’s CAT IV 600 V rating. In fact, the meter becomes a hazard that could arc, rupture, or explode.
DANGER: Given the hazards identified in this article, refer to OSHA starting with 29 CFR 1910.147 — The control of hazardous energy (lockout/tagout) and 29 CFR 1910 Subpart S — Electrical.
Do not work on energized equipment unless you are qualified, have a qualified safety partner, and follow all federal, state, and local regulations.
Key Takeaways
- Use the OEM-recommended fuse.
- An incorrectly selected fuse may cause an arc-flash hazard.
- The fuse is an integral part of the meter’s safety rating.
- Do not assume the fuse in your meter is purely a personal decision: the meter may be used by other personnel long after you are gone.
This article is part of the DigiKey Field Guide for Industrial Automation
Location: Measure It
Difficulty: 
Student — difficulty levels explained
Author: Aaron Dahlen | MSEE | Senior Applications Engineer, DigiKey
Last update: 06 Jul 2026
Which meters are included in this caution?
Many multimeters, such as the featured B&K Precision 390B and Fluke 87 V, are designed to measure current as well as voltage. These meters include fuses (Figure 1) to prevent damage when the operator unintentionally connects across a low-impedance voltage source.
The featured multimeters are best described as general-purpose meters. They are commonly included in the technician’s toolkit because they are useful for troubleshooting industrial automation equipment. Contrast these meters with specialized equipment that does not contain a fuse. The Fluke 283 FC is an example of this type of specialized instrument. It is designed to measure higher voltages with a CAT IV 1000 V rating. It does not contain a fuse as it does not measure current.
Other meters such as the Fluke 302+ do not include fuses. Once again, this is not a general-purpose tool. Instead, it is a clamp ammeter (no fuse required) along with a voltmeter and ohmmeter functionality.
Tech Tip: Fluke maintains this page to help you quickly identify the required fuse.
Figure 1: Image of fuses installed in a B&K Precision (left) and a Fluke multimeter (right).
Why is the wrong fuse dangerous?
The hazard is an accidental phase-to-phase or phase-to-neutral short through the multimeter’s current measurement path. This occurs when the meter is physically configured to measure current while the operator assumes they are measuring voltage. We forget that the leads are connected to measure current and not voltage.
In blunt terms, it is an all-too-human operator error.
The hazard is directly associated with the energy supplied by the source. For example, a 208 or 460 VAC phase-to-phase feeder capable of driving multi-horsepower motors can deliver a tremendous amount of energy. The multimeter manufacturers are aware of this problem and have taken precautions to protect the operator. In fact, the level of protection is written on the face of the meter and associated accessories such as probes. We see this as the meter’s rating such as CAT IV 600 V.
DANGER: The hazard still exists even when proper lockout/tagout is followed. For example, the meter is connected to measure the voltage using proper LOTO techniques. The fault could then occur when the system is energized. This is one of the reasons for the popularity of meters with remote display via cell phone app or dedicated remote display.
Primary and Secondary Fuse Failures
An incorrect fuse, unable to safely contain the arc breaking energy, may rupture and explode. But that is not the end of the story:
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The operator may be startled and accidentally come into contact with the feeder.
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The operator may be hurt by the explosion.
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In the worst case, the meter explodes and the arc is sustained. In milliseconds, the operator is exposed to arc flash and blast with life-altering consequences.
What makes a multimeter fuse special?
The multimeter and fuse are designed to gracefully fail in the event of a short circuit. This is true even when the source is capable of supplying high energy that would cause a normal fuse to explode.
Recall that fuses are rated across multiple dimensions:
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Voltage: Highest voltage to which the fuse can reliably extinguish an arc. Exceed the rated voltage and the fuse may not reliably open causing a sustained arc that can cause the fuse to explode.
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Breaking current: Maximum sustained current the fuse can withstand and reliably break at the given voltage. Higher currents will cause the fuse link to melt according to the fuse time-current curves. Note that “melting” is an understated term as high voltage and inductive loads tend to sustain the arc.
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Speed: A multimeter fuse will be fast so as to prevent damage to the meter’s printed circuit board traces. It also protects the meter’s probes.
Tech Tip: The time-current fuse curves carry an implicit assumption regarding energy associated with the fault event. For example, a 15 A fault in a non-inductive 12 VDC system results in a gentle melting of the fuse element. By contrast a 460 VAC phase-to-phase fault in a service panel containing inductive loads (motors) is a violent event. The slow melting is a quiet thermal event, while the sound of a phase-to-phase short is deafening.
Note that the fuse does not open instantaneously. For a brief moment in time, the current is limited only by the source impedance and resistance, the meter’s test leads, and the plasma generated inside the fuse. In the first case, the current is 15 A; in the second, the current may rise to hundreds or even thousands of amperes.
The Fuse is Designed to Contain the Explosion
The multimeter’s fuse is designed to contain the energy of the fault. Simply stated, the fuse must interrupt the circuit while withstanding the heat and pressure associated with the high-energy plasma. Note that the fuse body is not empty. It contains a granular material to absorb the plasma energy and help extinguish the fault.
To illustrate, consider Figure 2 which shows a fuse that has been cut in half. The most interesting part of the fuse is the body. It appears to be woven armor-like fiber-reinforced composite. This would allow expansion without being fragile. By contrast, a common glass cartridge fuse would overheat, crack, and likely fail to extinguish the arc.
Figure 2: Internal construction of a multimeter fuse.
Dangerous Practices
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Do not simply replace the fuse with the same unit that was installed. This is hazardous as a previous technician may have installed an incorrect fuse. Instead, always check the OEM literature to identify the correct fuse.
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Do not assume the meter is yours to modify with as you wish. While you may “know” what your meter is used for, you cannot guarantee the safety of other people in the shop. A technician on the night shift may use your meter for a quick measurement in a control panel. Also, meters have a very long life; some of us have meters that are 30 years old. That fuse decision you make today could risk the life of a technician who has not yet been born.
Parting Thoughts
We have all made the mistake of measuring voltage when the meter is configured to measure current.
It is an embarrassing mistake. It is also a costly mistake.
Accept the lesson and install the proper fuse.
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About This Author
Aaron Dahlen, LCDR USCG (Ret.), is a Senior Applications Engineer at DigiKey in Thief River Falls. His background in electronics and industrial automation was shaped by a 27-year military career as both technician and engineer, followed by over a decade of teaching.
Dahlen holds an MSEE from Minnesota State University, Mankato. He has taught in an ABET-accredited electrical engineering program, served as coordinator of an electronic engineering technology program, and instructed military technicians in component-level repair.
Today, he has returned to his home in northern Minnesota, completing a decades-long journey that began with a search for capacitors. Read his story here.