Unlike glass fuses, ceramic fuses are opaque, so you can't simply look through the body to check for a broken filament. The most reliable way to tell if a ceramic fuse is blown is to test it with a multimeter set to resistance or continuity mode. This blog post delves into practical techniques. Qualification testing includes electrical tests and physical test methods from MIL-STD-202, such as vibration, shock, salt-spray and moisture-resistance testing. Glass fuses may show a broken filament or dark discolouration inside the tube, but a clean failure leaves no marks at all. What Is a Ceramic Fuse? A ceramic fuse is a protective device used in electrical circuits to prevent overloads and. Its job is to open when current exceeds a safe value, protecting wiring and components from overheating, fire, or further damage.