Fake Bussmann multimeter fuses on Ebay DMM-B-44/100-R and DMM-B-11A

[voltlog]

As some of you might know already, the genuine Bussmann fuses purchased from a real distributor are not cheap at all they range between $8 and $20 depending where you get them from.

Some of you might have noticed there are Bussmann fuses being sold on Ebay/Aliexpress for way less, around $3 a piece but are these genuine or fake? To try and answer this question I did some tests where I compared a couple of genuine DMM-B-44/100-R and DMM-B-11A which were sourced from a distribuitor in Germany that gets them directly from Brymen to fuses I got from ebay.

The test included physical measurements like size and weight, the quality of the label printing, testing the fuse at the full rated current while measuring it's temperature, internal resistance and finally measuring the time it takes for the 440mA fuse to blow at 2A and comparing that with the datasheet graph.

The results showed that one of the two DMM-B-44/100-R sourced from Ebay performed exactly like it should and comparable to the genuine ones while one showed a breaking time of over 120ms. If you are interested in the tests performed here is a video of it. Of-course testing on such a small batch of units doesn't provide solid results but these are not cheap so it's the best I could do so far.



My theory is that these are really good fakes but with poor quality control thus some of the units are really bad. 
People also suggested in the comments that these could be factory rejects, like if they discover there is a bad fuse within a batch they discard the whole batch and that ends up being sold on ebay.
There is also a third theory (highly unlikely) that they are just Bussmann fuses made for the asian market so they are cheaper because of that.

I am also sending an email to Bussmann to see if I can get a response from them. I would like to hear your thoughts on the subject, maybe comments on the test method I used.

[Liteace]

Thanks for pointing it out, I only use my old fluke for automotive use so fake, cheap fuses are ideal for me

[HKJ]

Thanks for pointing it out, I only use my old fluke for automotive use so fake, cheap fuses are ideal for me

Safety wise it may be fine, but if you want you meter to last it may not be.
Fluke, like most other meters, has a couple of diodes to protect the mA/uA current resistors during overload, until the fuse blows. If the fuse is slow to blow they may not survive a fake fuse.
If you don't mind replacing a resistor and a few diodes if you are in bad luck (Probably only diodes or resistor), there is no reason to worry.

[Fungus]

Thanks for pointing it out, I only use my old fluke for automotive use so fake, cheap fuses are ideal for me

Safety wise it may be fine, but if you want you meter to last it may not be.
Fluke, like most other meters, has a couple of diodes to protect the mA/uA current resistors during overload, until the fuse blows. If the fuse is slow to blow they may not survive a fake fuse.

Pure speculation. Those meters are designed to withstand far more current then a car can provide. eg. The CAT III 1000V/CAT IV 600V rating means an 8000V spike with a 2 Ohm impedance, that's 4000 amps.

Even in a complete short circuit a car could maybe provide a few hundred amps at 12V. That's an order of magnitude less.

If you're worried you can always put in a fuse with a slightly lower current rating. 

PS: If you're regularly blowing fuses then consider getting a clamp instead.

[HKJ]

Pure speculation. Those meters are designed to withstand far more current then a car can provide. eg. The CAT III 1000V/CAT IV 600V rating means an 8000V spike with a 2 Ohm impedance, that's 4000 amps.

The issue is not absolute current, but current*time. What blows first: The fuse, the diodes or the resistor.
A careful manufacturer has, of course, checked it for many different voltages, but only with the correct fuse. Fuses that are slower to blow at some currents may mean damage to the resistor or diodes.
With my expensive meters I always use the correct fuse (I do blow fuses sometimes).

[Fungus]

Pure speculation. Those meters are designed to withstand far more current then a car can provide. eg. The CAT III 1000V/CAT IV 600V rating means an 8000V spike with a 2 Ohm impedance, that's 4000 amps.

The issue is not absolute current, but current*time. What blows first: The fuse, the diodes or the resistor.

Sure, but if it we're talking about voltage clamps that can withstand 8000V and 4000 amps for a millisecond then they can probably survive 12V and a couple of hundred amps for longer than that.

I guess it's down to how much you value your meter and how regularly you mess up and need the fuse.

[texaspyro]

I guess it's down to how much you value your meter and how regularly you mess up and need the fuse.

For me,  I've had two meter fuses blow in the last 50 (egad!) years... both due to faulty equipment being probed.   Think and double check before you probe!   If you are regularly blowing meter fuses you really need to up your metering skills.   Meters that beep when the probes don't match the meter settings are nice.

That said,  I have at least a dozen 440 mA and 11 amp HRC fuses and other appropriate fuses for all my meters... be prepared!  That reminds me... I need to get some of those tiny fuses for the AN8008's.

[Liteace]

I popped the fluke fuse a few months ago, checked current draw then done something else, then went to check voltage, put the dial in the correct place but forgot the test leads
I bought a cheap £8 meter that takes a standard glass fuse that I use now for current, popped the fuse on that a few times so now it's got the silver paper trick round the fuse, if the whole meter melts I don't mind chucking and getting a new £8 meter, it's cheaper than replacing the fluke fuse.

[voltlog]

For me the easiest way to pop a fuse is to forget the meter on amps, continue working on your circuit then wanting to measure a voltage you accidentally probe the circuit while still on amps mode.
Some people are very careful about this, others just make mistakes. However I would really like to know the real story behind these ebay fuses. For now I am waiting for a reply from Bussmann to hear their opinion on the subject.

[Fungus]

For me the easiest way to pop a fuse is to forget the meter on amps, continue working on your circuit then wanting to measure a voltage you accidentally probe the circuit while still on amps mode.

Hence bench power supplies with current limiting. The fuses in Flukes are there for when you make this mistake in an industrial environment, not when working with a 5V supply on your workbench.

But anyway, this has been said many times before. This thread is the story behind the fake fuses.

Are "fake" fuses really so bad? There's nothing really difficult about putting a piece of wire in a tube so why are the real ones so expensive?

[Neilm]

Are "fake" fuses really so bad? There's nothing really difficult about putting a piece of wire in a tube so why are the real ones so expensive?

The characteristics of real fuses are known and allowed for when designing. Real fuses are filled with sand to quench the arc formed when the fuse wire opens. You can't be sure of either of those facts with a fake fuse.

[Liteace]

Why not open a popped fake one to see what is inside

[voltlog]

Why not open a popped fake one to see what is inside

Did you watch the video?

[voltlog]

Real fuses are filled with sand to quench the arc formed when the fuse wire opens.

Yes, silica sand but as I've showed in my video, both genuine and ebay fuses had the same type of sand inside them.

[Fungus]

Real fuses are filled with sand to quench the arc formed when the fuse wire opens.

Sand is one of the cheapest substances on the planet.

both genuine and ebay fuses had the same type of sand inside them.

Other tests of these fuses have shown similar results. The fuses are quite well made but the breaking times are less consistent than the real ones.

[texaspyro]

Real fuses are filled with sand to quench the arc formed when the fuse wire opens.

Sand is one of the cheapest substances on the planet.

It wouldn't surprise me if they use fake sand.   

[voltlog]

Eaton/Bussmann replied and said that I need to send them the suspect fuses and their "quality team" will evaluate them and will get in touch with the manufacturing facility if needed.
I am now waiting for the details on where I need to send the parts exactly.

[joeqsmith]

Eaton/Bussmann replied and said that I need to send them the suspect fuses and their "quality team" will evaluate them and will get in touch with the manufacturing facility if needed.
I am now waiting for the details on where I need to send the parts exactly.

Very good.  Looking forward to seeing part 3!  I would tell them what you are doing if you have not already and ask if they would provide you with a small sample of good fuses for your destructive tests as well.   Doesn't hurt to ask anyway and it seems like good PR.

[tooki]

Eaton/Bussmann replied and said that I need to send them the suspect fuses and their "quality team" will evaluate them and will get in touch with the manufacturing facility if needed.
I am now waiting for the details on where I need to send the parts exactly.

Wow, you got a response? I contacted them about suspect counterfeit fuses and they ignored me.

[lordvader88]

I need some DMM-B-44/100-R, why is there a monopoly on these. Doesn't anyone else make DMM fuses like these For cheaper.

Is there any other fuse people use instead of these? I own a Brymen 869

[tooki]

I need some DMM-B-44/100-R, why is there a monopoly on these. Doesn't anyone else make DMM fuses like these For cheaper.

Is there any other fuse people use instead of these? I own a Brymen 869

At least three companies make them, IIRC: Littelfuse, Cooper/Bussmann, and SIBA.

The price varies wildly, from around $6 to $30.

[lordvader88]

Excellent, now back to world domination planning stages

[rauldm]

I bought in a website on Mexico, fuses for my Fluke meters, they sent fake fuses, these fuses can are identified really easy because the caps are completely false, also the paper tag just says "assembled in China"

[Mr. Scram]

I bought in a website on Mexico, fuses for my Fluke meters, they sent fake fuses, these fuses can are identified really easy because the caps are completely false, also the paper tag just says "assembled in China"

It doesn't even say Bussmann but Bassmann.

[rauldm]

Finally I got them from Grainger.