If you need replacing a fuse on your multimeter, you may find this reading useful. In this post I will share with you where you can buy cheap replacement ceramic fuses and how to make your DMM accept 5x20mm and 6x32mm fuses. I will also give some information regarding fuses and counterfeit fuses. In this case I am replacing the 1A fuse on a Uni-T UT61E multimeter, but this is applicable to most multimeters. You can read my review and teardown of the Uni-T UT61E multimeter here.
Ceramic vs. Glass fuses
The Uni-T UT61E, like many "better quality" DMM's, uses ceramic fuses. Ceramic fuses are better than the more common and cheaper glass fuses. They have a feature called High Rupture Capacity (HRC). Ceramic fuses have a ceramic tube, and all the empty space inside is filled with sand. If a very high current occurs, an extremely high amount of heat is created inside the
fuse. That heat melts the sand filling of the fuse into glass.
Since glass is an insulator, it suppresses any arc-over instantaneously. This behaviour minimizes the possibility of a dangerous high arc current, which is what happens if a normal glass fuse fails to break a
heavy fault current. Unlike sand filled ceramic fuses, if a very high arc current goes through a common glass fuse, it can generate an explosion that shatters the fuse and lead to damages and serious injuries.
Sources of 6x25mm ceramic fuses
The Uni-T UT61E uses two ceramic fuses, one 6x25mm 10A and one 6x25mm 1A. The original fuses are branded AsiaFuse BS1362. Unfortunately, it turns out that cheap BS1362 6x25mm ceramic fuses are hard to find. The more common BS1362 6x32mm fuse size is available from multiples sources though. And since the Uni-T UT61E PCB layout accepts 6x32mm fuses also, it's just a matter of moving one of the fuse holder terminals to a different position. Take a look a the following picture.
In the above picture, since a 6x25mm fuse was not available, I managed to use a 5x20mm glass fuse temporarily while my order of 6x25mm ceramic fuses did not arrive. It was a matter of carefully tightening the fuse support until it hold the smaller 5x20mm fuse securely in-place.
These are the BS1362 ceramic fuses I received from AliExpress. They are branded Bussmann and costed US $2.50 for a pack of 10. And here is the Uni-T 61E after the 1A fuse was replaced.
Unfortunately, after careful inspection and despite apparent good build quality, the fuses I received appear not to be genuine. However, since I determined they are safe to use (read below), I'm happy.
Buy BS1362 ceramic fuses from Banggood!
Counterfeit fuses
Since branded ceramic fuses are much more expensive than glass fuses, there are counterfeits with varying levels of quality. In many cases it's very hard to tell if a ceramic fuse is genuine or not. One can visually inspect and compare the suspect fuse with an original fuse sourced from a reputable distributor. If you buy a set of ceramic fuses I recommend you open one to see if it is really filled with sand. Needless to say, counterfeit fuses can be dangerous!
BS1362 Fuse Specs Datasheet
Counterfeit Fuse Information
Review of Uni-T UT61E
