Some study materials have been restricted for members only.
To get access, please contact us at firstname.lastname@example.org
1. Demonstration of correct procedure for replacement of fuse.
i) Switch off the power supply for the equipment.
ii) Make sure the equipment is grounded.
iii) Make sure that hands are not wet.
iv) Wear insulating gloves.
v) Replace the fuse with an equivilant current rating.
vi) If the fuse of equivilant current rating is not available, then use the fuse of slightly lesser
Note - 1) If the fuse of equivilant current rating is not available then we use the fuse of
slightly lesser current rating because if we would have used the fuse of higher
current rating then in case of over current the main purpose of the fuse will be
defeated as a sacrificial device and the equipment can be easily damaged.
If the fuse of lesser current rating is used then in case of over current it works
as a circuit breaker and hece protects the equipment.
2. Checking Condition of the Fuse.
i) Transparent cylinders (glass or plastic) have a wire running through the middle. If the wire
is broken, the fuse is blown. If the whole cylinder is scorched black or brown, the fuse is
blown and there may be a major short on the circuit that needs repair (especially if the
replacement fuse blows after a short time). The fuse can be tested by two methods:-
a) Test continuity if available - Most digital multimeters have a continuity setting, which is
labeled with a series of parallel arcs: ))). Turn the dial to this setting, then place the two
probes at opposite ends of the fuse. If you hear a constant beep while they are touching
the fuse, the fuse is still good. If you don't hear anything, the fuse is blown.
b) Set the multimeter to test resistance - This setting looks like the Greek letter omega Ω.
The resistance setting sends a small current through the fuse, and tests how much
current goes through. We don't really care about the exact resistance reading, but if the
fuse is blown, we won't get any resistance reading because the current will not be able to
pass through the broken wire.