Fuses are often overlooked when it comes to electrical testing equipment safety. Yet as a protection against electrical shock and overheating wires, using the right fuse for the job is critical. Taking voltage and current measurements with a tester that does not have the fuse protection that was designed into the tester is extremely dangerous and can cause serious burns and possible death. Fuses matter to safety and picking the right fuse is crucial. Be sure to:
Use fuses the engineer designed into the testing equipment
For your own safety you need to be sure the fuses you use are the ones the engineer designed into the tester. Always refer to the tester's manual, or check with the tester manufacturer to ensure you have the correct fuse. Your safety is worth much more than the money it takes to purchase the proper fuse for which the tester was designed.
Don’t make the beginner’s mistake of substituting inferior fuses once the originals fail, and don’t ever disable the fuse on a job.
Use high energy fuses approved by the meter’s manufacturer
High-energy fuses are designed to keep the energy generated by an electrical short within the fuse enclosure, thus protecting the user from electric shock and burns.
These high-energy fuses are designed to limit the length of time the energy is applied and the amount of oxygen available for combustion.
In addition to the specially designed fuse element, the high energy fuse is filled with sand. The sand will not only help absorb the shock energy created by the exploding element, but the high temperatures (up to 10,000°F) generated by the energy will melt the sand and turn it to glass. The glass coats the element and smothers the fireball by cutting off the available oxygen, keeping you and the tester safe from harm.
Not all fuses of the same amperage and voltage are the same.
Use fused test probes for additional protection
A fused test probe has built-in replaceable fuses. Fused probes provide protection to those using multimeters that lack built-in fused protection.
Fused test probes help protect against arc blast and fire when making voltage or current measurements, as well as against transients on a measured circuit when the transients exceed the capability of the instrument to withstand transients—such as when lightning strikes.
Use safety-rated fuses
You don’t want a meter that uses just any old fuse. Specially designed high-energy fuses dissipate stray voltage before it reaches you and are designed to blow in time to get you out of harm’s way.
If your digital multimeter meets today's safety standards, that fuse is a special safety sand fuse designed to pop before an overload hits your hand. When you change your DMM fuse, be sure to replace it with an authorized fuse.
Manufacturers specify the required amperage, interrupt and voltage ratings for replacement fuses for a reason. If you select a fuse without these ratings you put your safety and the safety of those around you in jeopardy.
For more information on Electrical Safety, see our online course available at the Fluke eLearning Center.