Fuse Condition Monitor with LED Indicator

In the field of electrical and electronics engineering, a fuse (short for fusible link) is considered as a safety tool to protect any electrical circuit from the result of overload currents. It consists of a very thin metal wire or strip that melts or vaporizes when excessive current flows within. The thin wire may be constructed out of aluminum, tin-coated copper or nickel. Most fuses on electronic equipment are cylindrical glass or ceramic type with a metal cap on both ends.

Together with other overcurrent devices, fuses are crucial elements in a power distribution system to avoid damage, overheating or fire. This is done by opening the circuit under extreme current conditions. The maximum rating of a fuse for a given circuit is determined by the wiring regulation.
The circuit shown was designed to test the life span of a fuse using a resistor and LED as a visual indicator.
Under out of order conditions of the fuse, LED1 illuminates as the current starts to travel and be controlled by R1 to a safe level. This indicates that the fuse have been “blown” or in an open circuit state. The fuse operates in a short-circuit manner wherein it allows the passage of normal currents. Another way of testing the fuse, even while it is still in circuit, is by testing the continuity of the fuse using a multimeter that reads zero ohm for good fuse and that reads infinity when broken.
Source:www.zen22142.zen.co.uk/Circuits/Power/fusemon.htm