Fuses are electrical safety devices which breaks the circuit in case of any over voltage.
People visually check the fuses, if the fuse is broke. It wouldn’t work all the time, even if the fuse isn’t broken doesn’t mean that the fuse is fine for working.
Therefore, checking a fuse with an Ohmmeter or a continuity tester is important rather than assuming it is good. A significant percentage of all “dead” circuit boards have nothing wrong with them except a blown fuse.
Why test a Fuse?
Some fuses were not cheap, and if a replacement is not handy, it means a trip to the auto parts store or home improvement store. It’s a regular part of troubleshooting strategies instead of just fixing fuses that don’t know are blown for sure.
It’s a very simple task to check a fuse to see if it’s actually blown, requiring a minimum of inexpensive tools, and can save both money and time.
A fuse testing device is nothing more than a continuity check device. It can be a multimeter, a continuity test, or a dedicated fuse tester.
However, the idea is to send a small current through the fuse; the fuse is good if it goes through the fuse. If it doesn’t blown, the fuse will need to be replaced.
Fuse test procedure:
In addition to the visual test, the other way to check whether or not the fuse is blown is by doing an electrical test to check continuity from one end of the fuse to the other.
By taking a multimeter and placing it in continuity mode, you do this. You place one on one end of the fuse and the other on the other end of the fuse.
There are two possibilities:
If the screen reads a stray value (in ohms), the fuse is in good condition (in the image above it is 1.5 ohms)
If the display reads the resistance state of 100%, i.e. the cost 1, the fuse will be blown.
For all types of fuses, this process is the same. The aim is to test the filament resistance within the fuse. The fuse is theoretically useless if the multimeter displays 100 percent resistance. In this scenario, you can replace it with a new one immediately.
If you want to test a fuse when connected to a circuit / system, be sure to switch the circuit / system off before checking. This is designed to prevent shock or short circuit.
If your multimeter does not have a continuity mode, the multimeter ohmmeter can also be used to test the fuse. Place the multimeter on the setting of the ohmmeter and place the leading probe across the fuse’s 2 ends. If you get a very low reading, a few ohms, then the fuse is continuous and, thus, fine.
If there is very high reading, such as extreme Megohms, the fuse is broken and, thus, poor, and should be replaced.