Multimeter fuses

[iXod]

11A fuse for EEVblog BM235: US$41.00. Not for a box of 5. Each.

http://www.digikey.com/product-search/en?keywords=DMM-B-11A

Next meter, Dave, use tin foil! lol

Can't imagine Bussmann's justification for such a price. Is it that much quicker than other fuses? Gold filament?

edit:
Digikey offered this as alternative:

http://www.digikey.com/product-search/en?keywords=614-1078-ND

All but the "B" in the pn... and US$9.

Good alternative?

Cheers.

[Fungus]

Never mind that, tell us how you managed to blow it. 


PS: Look on the bright side: You'll be a lot more careful next time.

[joeqsmith]

Just plugged it into Amazon, 5pc for $26.   Looks like you can buy singles. 

https://www.amazon.com/BUSSMANN-DMM-B-11-DMM-B-11A-Multimeter-Replacement/dp/B007HQX502/ref=sr_1_13?ie=UTF8&qid=1467855633&sr=8-13&keywords=dmm-b-11

[retiredcaps]

Just plugged it into Amazon, 5pc for $26.

Just a word about Amazon.  Since they allow 3rd party sellers, you have to be really careful and do your homework on the seller. Some sellers sell fakes, but Amazon either doesn't care or can't screen out the bad sellers quick enough.  Some sellers are NOT based in the USA which means you are waiting 3 to 5 weeks.

If you are buying from Amazon, I look to ensure it is fulfilled by Amazon itself.

[BMack]

Just plugged it into Amazon, 5pc for $26.

Just a word about Amazon.  Since they allow 3rd party sellers, you have to be really careful and do your homework on the seller. Some sellers sell fakes, but Amazon either doesn't care or can't screen out the bad sellers quick enough.  Some sellers are NOT based in the USA which means you are waiting 3 to 5 weeks.

If you are buying from Amazon, I look to ensure it is fulfilled by Amazon itself.

Keep in mind that just lowers your risk, it does NOT guarantee a legitimate product.

[retiredcaps]

If you are buying from Amazon, I look to ensure it is fulfilled by Amazon itself.

Keep in mind that just lowers your risk, it does NOT guarantee a legitimate product.

True, but at least you then can deal with their legendary customer service vs some 3rd party seller.

[BMack]

If you are buying from Amazon, I look to ensure it is fulfilled by Amazon itself.

Keep in mind that just lowers your risk, it does NOT guarantee a legitimate product.

True, but at least you then can deal with their legendary customer service vs some 3rd party seller.

Agreed

[iXod]

Keep in mind that just lowers your risk, it does NOT guarantee a legitimate product.

True, but at least you then can deal with their legendary customer service vs some 3rd party seller.

Best to not have to deal with *any* CS--legendary or not--to have a fried DMM replaced, if the fuse is counterfeit. One area I'd rather not have to worry.

I'll order from Mouser.

iX

[nanofrog]

Digikey offered this as alternative:

http://www.digikey.com/product-search/en?keywords=614-1078-ND

All but the "B" in the pn... and US$9.

Good alternative?

Cheers.

I suspect it's the same fuse with a custom P/N for Fluke (gR characteristics for the filament). 

FWIW, a Siba 5019906.11 would work as well. Generally speaking, they're cheaper than the B version, but more expensive than the Fluke version (here).

Unless you buy directly from Keysight for $5.79 that is (internal P/N is 2110-1402).      They offer the 440mA version for $6.48 as well (2110-1400).

BTW, it's free shipping back when I needed one when it was still Agilent (suspect it's the same). Got in too much of a hurry and blew one by not moving the lead from the A input to the V/Ohm/,... input when trying to measure voltage when working on a Jeep. 

[David Hess]

The reason these fuses are so expensive is that they have to be able to interrupt high voltage DC while not arcing.  For instance common 250 volt AC rated fuses are only good to like 32 volts DC.

[Berni]

The reason these fuses are so expensive is that they have to be able to interrupt high voltage DC while not arcing.  For instance common 250 volt AC rated fuses are only good to like 32 volts DC.

True these proper HRC fuses will interrupt massive fault currents safely versus the regular cheep glass fuses that tend to explode and draw the arc out in to the surroundings.

But why are they so much more expensive? Id assume its just a matter of using a better wire material inside and filling it with sand to absorb the energy.

[iXod]

But why are they so much more expensive? Id assume its just a matter of using a better wire material inside and filling it with sand to absorb the energy.

Certainly not the cost of components that justifies the retail price. I'm sure it's that meter owners know that to use a non-DMM rated fuse is risking damage so they can charge whatever they want.

iX

[MosherIV]

But why are they so much more expensive? Id assume its just a matter of using a better wire material inside and filling it with sand to absorb the energy.

Proving regulatory compliance. Good quality control, testing batches of fuses to prove they do their job (considering how small the volume is for this kind of fuse, compared with the cheaper ones, this may be a considerable cost in their manufacture).
All the red tape costs money.
All so that you know the fuse does what it says on the case.

[Fungus]

The reason these fuses are so expensive is that they have to be able to interrupt high voltage DC while not arcing.  For instance common 250 volt AC rated fuses are only good to like 32 volts DC.

Yep, we get that.

But what makes them expensive? There's no high tech inside them. It's basically just a fuse filled with sand to prevent formation of a plasma arc when there's enough energy to vaporize the wire instead of just melting it.

All the red tape costs money.

That might explain some of it but I think there's a large amount of charging extra just because they can.

They're not like aircraft parts where every single nut and bolt has its own audit trail.

[DenzilPenberthy]

I'd say they are exactly like aircraft parts in that they are a safety component which if it does not perform as expected then someone will very likely be maimed or killed.  Put a normal 32mm glass fuse in a multimeter, set it to Amps range then put the probes across two phases of a large 3 phase busbar and see what happens!

They are expensive for all of the same reasons that an aircraft bolt is more expensive than one from an ebay hardware shop

[Fungus]

I'd say they are exactly like aircraft parts in that they are a safety component which if it does not perform as expected then someone will very likely be maimed or killed.  Put a normal 32mm glass fuse in a multimeter, set it to Amps range then put the probes across two phases of a large 3 phase busbar and see what happens!

The concept is the same, yes.

They are expensive for all of the same reasons that an aircraft bolt is more expensive

Not really. Aircraft bolts are expensive because of the supply logistics and the paper trail they leave behind behind them. These fuses don't have that.

[markce]

Funny things thse fuses. I've a large number of fuses installed in all kind of equipment, test and consumer.
They never blow, so why worry.
I once blew the 440mA fuse in my Fluke DMM when it was very new. It's expensive, but part of my personal safety
using this meter, so I accept a higher price. The price itself makes me think twice when using current settings,
thus increasing safety...

[David Hess]

I have blown these fuses in the past and when I needed an immediate replacement, I soldered 3 strands from 7/32 stranded 24 gauge wire across the fuse caps to make a 20 amp fusible link.

I wonder if the fuse construction is more than embedding the fuse element inside of sand.  Could the granular material decompose when heated by the arc outgassing to extinguish it?

[retiredcaps]

I wonder if the fuse construction is more than embedding the fuse element inside of sand.

Modemhead took apart a Bussmann fuse after an oops moment.

http://mrmodemhead.com/blog/inside-a-multimeter-fuse/

[Fungus]

I wonder if the fuse construction is more than embedding the fuse element inside of sand.

Nope.

Could the granular material decompose when heated by the arc outgassing to extinguish it?

Nah, there won't be enough heat from the fuse wire to turn the sand to plasma.

The air around the fuse is probably more conductive once the fuse vapor has dispersed into the sand .

The price itself makes me think twice when using current settings, thus increasing safety...

Yep. It certainly teaches you how to use a multimeter safely.

[Refrigerator]

Copper wire across the fuse terminals gets the job done and lets you know when it blows

[Bobson]

I'm using ceramic Bussmann TDC-180 10A fuses with my cheap Chinese multimeters instead of glass ones. They are plenty from unused UK power plugs coming with almost any bit of equipment.

May be I'm wrong and it it safer to leave glass fuses? Data chart says these Bussmanns are Fast/Medium types, rated voltage 264V AC.

And what is "Bussmann" exactly? Is it type of fuse or trademark? Because I see a lot of Bussmann fuses from different producers (may be just resalers).

[nanofrog]

And what is "Bussmann" exactly?

A brand name now owned by Eaton (link to fuse products).

[Fungus]

May be I'm wrong and it it safer to leave glass fuses?

I don't think glass fuses are ever better.

(apart from the fact that you can look through the window and see if they're blown)

They are plenty from unused UK power plugs coming with almost any bit of equipment.

In that case there's a fun/simple way to find out: Blow a few of them. 

Put your meter in the milliamps range and connect the probes to a battery. If the fuse blows then they're OK to use in your meter.

Data chart says these Bussmanns are Fast/Medium types, rated voltage 264V AC.

Those fancy fuses are only there in case you connect your meter to a high energy source with the selector in the "amps" position.

Connecting your meter to a high energy source with the selector in the "amps" position is something you should never do in real life. There's no legitimate reason to do it. Ever.

The fuses are only there for moments of stupidity.

On all ranges except "amps" it's it MOVs, PTCs, etc. that protect you., not the fuses (Simple test: pull the fuses out and see if you can still measure volts, ohms, etc.)

Bottom line: If your meter isn't safe to use with mains electricity then changing the fuses won't fix that.

[David Hess]

Could the granular material decompose when heated by the arc outgassing to extinguish it?

Nah, there won't be enough heat from the fuse wire to turn the sand to plasma.

The air around the fuse is probably more conductive once the fuse vapor has dispersed into the sand .

Is it actually just sand though?

I found two materials used in combination for arc quenching in fuses but there are others depending on the application.  Silica melts and aluminum hydroxide decomposes producing water which itself decomposes into other gases increasing the dielectric strength and blowing out the arc.