Fuse Testing
Fuses are really just wires that are designed not to last, but their purpose is to prevent damage to more valuable electrical equipment or prevent fires (especially in homes) caused by power surges. If too much power runs through the fuse, it will "burn out," quite literally, and open the circuit, preventing the current from flowing through the circuit. There are several varieties of fuses, but their differences are primarily in appearance.
The cartridge fuse is a cylindrical fuse that has been common in a wide variety of devices for many years, from homes to small electronic devices. They have metal contact or terminal points on either end and consist primarily of a tube that contains the wire.
1. For testing a fuse, (a) use it to measure the continuity (which tests if the circuit is complete):
Turn the dial on the multimeter so it points to the continuity setting, which looks like 5 curved vertical lines. Before testing the fuse, put the positive and negative leads together and listen for the meter to beep to ensure it’s working properly.
• Put one lead (positive lead is inserted in VΩmA input jack or port and negative lead is inserted in COM input jack or port of multimeter) on each end of the fuse.
Because the fuse is little more than a single wire—and no complex parts to worry about—it does not matter which side receives the positive or negative lead.
• Listen for the multimeter to beep continuously as you hold the probes against the fuse. If any noise can’t be heard from the meter, then the fuse is blown.
2. (b) or the ohms (which tests resistance) : go to the multimeter setting that has the omega symbol (Ω).
A multimeter has a positive and negative lead. When testing resistance in a circuit, the meter will transmit a small quantity of electricity from its own battery and then measure the amount that passes through the circuit or object.
When measuring resistance, touch the probes together to get an initial reading. Then, put the probes on either side of the fuse and check if the reading is similar. If it is, then the fuse works properly. If you get no reading or “OL”, then the fuse has blown.