Inside HRC fuses: cheap vs brand-name

An unrelated fuse blew in another multimeter, so I decided to buy some replacements for these white ones too. Previously I was using cheap eBay replacements. No *electrical* comparison/testing is done in this post.

Fuses we are tearing down today:

• SIBA branded 5x20 0.5A from RS-online
• Unbranded generic “5x20 0.5A ceramic” off eBay

Skippable Backstory

My Extech MN16 multimeter takes a 0.5A 5x20mm fuse. Last time this blew (read: a friend borrowed it) I ordered some cheapies to replace it off eBay. When a fuse in another multimeter died, I decided to order some ‘branded’ replacements from RS components for the MN16 too.

Sidenote: although this multimeter calls for 660V rated fuses, I have had no luck finding them in the 5x20 form factor. Instead I have been installing ones rated to only ~230V. Not perfect, but the best I can do.

Outside Appearance

Looking side-on:

I can’t remember which way around they were supposed to be in this diagram. Both have slightly ill-fitting endcaps and come in deluxe white.

When we look at the fuses end-on however things become a bit clearer. On the left is the unbranded, on the right is the German:

Inside Appearance

Whole fuses? Nothing a pair of sidecutters can’t fix.

Unbranded:

SIBA:

Notice the sand? You could play with Tonka trucks in the SIBA whilst the unbranded was bare-bones empty. Apart from that they look very similar and have identical-looking fuse wires:

Why is there a beach in my fuse?

It looks like the sand is there to quench arcs better than air does. I have no experience with this or testing it, so I can’t back this up.

More fuse porn

The fuses I needed to order in the first place:

Some others I now have lying around:

Shame I can’t fit these in my DMM. Perhaps I should make a DMM inside them.