Author Topic: Multimeter fuses  (Read 38825 times)

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Offline joeqsmith

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Re: Multimeter fuses
« Reply #25 on: July 10, 2016, 06:04:43 pm »
I would not mind getting my hands on various fake fuses to play with.  If you have a known source on Amazon that will sell them, post it or PM me.   

John Ward had ran some tests on some fakes.  It make be interesting to try and run some similar tests on the large HRC fuses used in the meters.   



Online Fungus

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Re: Multimeter fuses
« Reply #26 on: July 11, 2016, 05:49:16 am »
I would not mind getting my hands on various fake fuses to play with.  If you have a known source on Amazon that will sell them, post it or PM me.   

There's loads on eBay. Don't know about Amazon though.

John Ward had ran some tests on some fakes.

They weren't much worse then the 'real' ones.

OK, some smoke came out of one of them :D but the times, breaking currents and maximum temperatures weren't that different. Not enough to be the difference between life/death.
 

Online Berni

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Re: Multimeter fuses
« Reply #27 on: July 12, 2016, 06:05:18 am »
A glass fuse will work here just fine.

What i want to see tested is interrupting large fault currents. That's where a glass fuse dangerously explodes while a proper HRC fuse should contain it and stop the arc safely.

I do have a sizable capacitor bank(i think about 800 Jules at 450V) that could provide enough power to explode fuses, but these fuses tend to be a bit expensive to blow up a dozen of them.
 

Offline Richard Head

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Re: Multimeter fuses
« Reply #28 on: July 12, 2016, 07:54:15 am »
The silica sand in HRC fuses is used to displace the air. If the air (gas) is removed there is no significant pressure build-up inside the fuse and it doesn't explode.
 

Offline joeqsmith

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Re: Multimeter fuses
« Reply #29 on: July 12, 2016, 08:31:28 am »
I was hoping that with as many fake DMM HRC fuses there were on Amazon, I would get some leads from those of you that bought them.   The only ones I saw where people had made them were the smaller sizes like John shows.   

Assuming they could be found for a fair price, would have been fun to get 5/ea of various ones and bench mark them.  Maybe a tear down, 2 at DC and two at their fault currents (using a scope to capture what is going on).   Drag out the faster camera.

One of the glass ones in the VICI 99:
https://youtu.be/Q23eArAsXmo?t=1845

Small glass and ceramic fuses on the half cycle simulator:
https://youtu.be/cWKoRxNEsXk?t=90


Of course, photonicinduction does a much better job using some much higher rupture current fuses:
https://youtu.be/0-HYPdh744M?t=342





Online Berni

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Re: Multimeter fuses
« Reply #30 on: July 12, 2016, 10:22:58 am »
I looked in to it a bit and i see that the small HRC fuses found in good multimeters tend to have about 20kA breaking capacity. So my capacitor bank does not have nearly enough grunt to cause a genuine HRC fuse to fail catastrophically.

Issue is that you need a low voltage cap bank for the test to be valid as the fuses tend to be rated up to 400 VAC. So to get 20kA of peak current out of it the cap bank has to have both low resistance and inductance along with quite a bit of jules to sustain that for one 50Hz cycle.

If anyone thinks they have a cap bank that fits the bill id love to see some testing.
 

Offline JackM

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Re: Multimeter fuses
« Reply #31 on: July 12, 2016, 02:18:09 pm »
Where can one buy genuine HRC fuses in Canada? Digikey.ca offers no alternatives aside from the Bussman/Eaton brand which they sell for $47 CAD (440mA) and $57 CAD (10A) each... Mouser has a cheaper Schurter brand 10A fuse, but I'm having a hard time finding alternatives for the 440mA fuses from a reputable source.
 

Offline retiredcaps

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Re: Multimeter fuses
« Reply #32 on: July 13, 2016, 02:56:49 am »
Where can one buy genuine HRC fuses in Canada?
Littlefuse also makes 440mA fuses that are used in high end meters.

A quick search shows Newark sells the 440mA fuse for $9.80 CDN.

http://canada.newark.com/fluke/943121/fuse-replacement-440ma-fast-acting/dp/52F4514

Newark has the 11A fuse for $13.02 CDN.

http://canada.newark.com/fluke/803293/fuse-only-replacement-11a/dp/20C4137

I have NO IDEA what Newark charges for shipping and what courier they use.
 

Online Fungus

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Re: Multimeter fuses
« Reply #33 on: July 13, 2016, 03:50:30 am »
Where can one buy genuine HRC fuses in Canada?
Littlefuse also makes 440mA fuses that are used in high end meters.

And SIBA: http://www.ebay.com/itm/201613339114


 

Offline joeqsmith

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Re: Multimeter fuses
« Reply #34 on: July 13, 2016, 03:59:38 am »
I looked in to it a bit and i see that the small HRC fuses found in good multimeters tend to have about 20kA breaking capacity. So my capacitor bank does not have nearly enough grunt to cause a genuine HRC fuse to fail catastrophically.

Issue is that you need a low voltage cap bank for the test to be valid as the fuses tend to be rated up to 400 VAC. So to get 20kA of peak current out of it the cap bank has to have both low resistance and inductance along with quite a bit of jules to sustain that for one 50Hz cycle.

If anyone thinks they have a cap bank that fits the bill id love to see some testing.

None of the 10mm ones I have seen were rated for 400V. 

SIBA, 50-199-06, 10A, 1000V 30kA, made in Germany, solid
Littlefuse, FLU 11A, 11A, 1000V 20kA, assembled in Mexico, woven
Littlefuse, FLU 44/100A, 440mA, 1000V 10kA, assembled in Mexico, woven
Cooper Bussmann, DMM-B-44/100, 440mA, 1000V, 10kA, woven
Fluke packaged Bussmann, DMM-44/100, 440mA, 1000V, 10kA, assembled in Mexico, woven

That large cap Photonicinduction shows to blow one apart would be the ticket.  Best to know what your doing if you wanted to buy one to play with.   I know my tiny half cycle generator would not come close to making any of them explode.   

If I could get some of these fake Amazon fuses, these may actually come apart by the sounds of it. 

Online Berni

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Re: Multimeter fuses
« Reply #35 on: July 13, 2016, 05:23:52 am »
Also the question is at what point do you genuinely need a proper fuse in your meter.

If you work with only low power things then there is no real danger of using a cheap meter with the cheap fuse it comes with. And if you work with large industrial switch panels designed to carry 1000s of amps in normal operations you obviously shouldn't even come close with anything other than a proper high quality meter with proper fuses.

But at what point does a HRC fuse become a must. Like for example a lot of people use meters to troubleshoot there home mains wiring. Is there enough energy in a wall outlet to blow apart a meter? How about the incoming mains in the fuse box?
 

Online Fungus

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Re: Multimeter fuses
« Reply #36 on: July 13, 2016, 12:19:39 pm »
Also the question is at what point do you genuinely need a proper fuse in your meter.

This is an elephant in the room.

If you work with only low power things...

Not only that but the fuse is only in the low-impedance ranges on the meter, ie. amps. If your meter isn't set to an "amps" range then the fuse does nothing at all. You can take it out and the meter will still measure volts, ohms, etc.

I can't think of a legitimate reason to connect the meter to a high energy source in the amps range.

Bottom line: The fuse is only there for when you're not using the meter correctly. If you're using it correctly then the type of fuse is unimportant. Worry more about them MOVs, PTCs and creepage distances.

« Last Edit: July 13, 2016, 12:24:33 pm by Fungus »
 

Offline joeqsmith

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Re: Multimeter fuses
« Reply #37 on: July 13, 2016, 12:32:14 pm »
Not only that but the fuse is only in the low-impedance ranges on the meter, ie. amps. If your meter isn't set to an "amps" range then the fuse does nothing at all. You can take it out and the meter will still measure volts, ohms, etc.

I can't think of a legitimate reason to connect the meter to a high energy source in the amps range.

Bottom line: The fuse is only there for when you're not using the meter correctly. If you're using it correctly then the type of fuse is unimportant. Worry more about them MOVs, PTCs and creepage distances.

 :-+  Agree 100% and this is why I never included the current in my transient testing.   Theses HRC fuses are there for safety.   

Online Berni

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Re: Multimeter fuses
« Reply #38 on: July 13, 2016, 12:50:22 pm »
Yes the fuse is there only for the time when you stupidly forget you are plugged in to amps and try to measure the voltage of a supply. Just when the said supply is a 12V wall wart all you get is a bit of a spark and the wallwart getting warm. When you do this on a giant 3 phase bus bar the result is a huge arc flash and the chard remains of the electrician that did the stupid mistake.

Voltage overloads in multimeters are usually not as concerning since you rarely encounter more than 1000V at home and if you do it tends to be low current. So as long as you don't try to measure the output of a microwave oven transformer you should be safe.

The question is if a DIYer does the same amps jack mistake in his home mains distribution panel. Could a cheep meter and fuse become more dangerous in such a situation versus a HRC fuse?

I personally never have taken care of using only good quality meters on regular household 230/400V mains. I picked up whatever meter was handy, be it my good Agilent or the cheap 20€ rebadger.

 

Offline helius

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Re: Multimeter fuses
« Reply #39 on: July 13, 2016, 01:03:41 pm »
It's slightly overstating it to say the fuse is only for when you misuse the meter. If the power-consuming circuit element that you are measuring current for were to fail short, then the meter itself would become the driven device; the fuse protects you from that situation, too.
For example, you are using the DMM in amps mode to measure the performance of a dummy load connected to a 1KW supply. What happens when the load fails short?
 

Offline joeqsmith

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Re: Multimeter fuses
« Reply #40 on: July 13, 2016, 01:21:43 pm »
It's slightly overstating it to say the fuse is only for when you misuse the meter. If the power-consuming circuit element that you are measuring current for were to fail short, then the meter itself would become the driven device; the fuse protects you from that situation, too.
For example, you are using the DMM in amps mode to measure the performance of a dummy load connected to a 1KW supply. What happens when the load fails short?

There are shitty glass fuses then there are HRC fuses.   Both can protect the meter from damage.    Seeing you're providing example, for your 1KW supply assuming it is a 100,000V,  my guess is the meter would lug down the supply.  I guess you could try it and post your results. 

The question is if a DIYer does the same amps jack mistake in his home mains distribution panel. Could a cheep meter and fuse become more dangerous in such a situation versus a HRC fuse?

I personally never have taken care of using only good quality meters on regular household 230/400V mains. I picked up whatever meter was handy, be it my good Agilent or the cheap 20€ rebadger.

I am not sure what a worst case number would be for how much energy you could have across the incoming lines to your house.   :-//   I have seen some meter's cases open up and others with sparks coming out and even some leads that ruptured with some fairly low energy transients. 

I would not be too surprised if some of the meters I looked at could have a fair amount of damage in the current settings, even with the fuses removed.   

Too many variables.   But I would be very interested if you come up with some sort of test and run it. 

Online Fungus

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Re: Multimeter fuses
« Reply #41 on: July 13, 2016, 04:19:00 pm »
For example, you are using the DMM in amps mode to measure the performance of a dummy load connected to a 1KW supply. What happens when the load fails short?
You need a fuse, sure, but does it need to be one of those expensive Bussman fuses? A simple glass fuse can interrupt 1kW.

The Bussman fuses are for situations where there's thousands of amps available, where a glass fuse will turn to metal vapor inside the tube.
 

Offline MacMeter

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Re: Multimeter fuses
« Reply #42 on: January 28, 2017, 05:18:41 am »
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.

I've just run into this dilemma, I was shocked to see the large fuse costing 1/3 the price of the meter.

There are a few threads here about this, and I posted the same request (below) in case anyone reads those old threads. Seeing such a price decrepancy made me realize the fake/clone market For these is a real concern. I'm not going to get into the debate if "similar" fuses are ok, or good enough. In my use, there are times I might rely on them, so I'd like to find the original spec'd fuses at a reasonable price, if that's even possible?

Anyone find a reputable online company, (I'm in the US) that sells both types of replacement fuses at reasonable prices? BM235 model.

I looked at both Mouser, and GreyBar, both large companies, but a single large fuse is over $40/each, and of course I can find them on eBay, for far less, but I have no idea if they are Chinese clones, since China is the source. The price range between them is crazy, 3 large fuses cost as much as the base meter. THANKS!
 

Offline joseph nicholas

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Re: Multimeter fuses
« Reply #43 on: January 28, 2017, 10:02:25 am »

Voltage overloads in s are usually not as concerning since you rarely encounter more than 1000V at home and if you do it tends to be low current. So as long as you don't try to measure the output of a microwave oven transformer you should be safe.


Measuring this voltage I just use my cheap chinese MF-47 multimeter.  It goes up to 2.5KV.  It also has a seperate jack for this measurement so its hard to fuck it up.
 

Offline mmagin

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Re: Multimeter fuses
« Reply #44 on: January 28, 2017, 01:14:59 pm »
It may be bad luck saying this, but I've not yet blown a fuse in a DMM.  I've actually destroyed the tip of one of the probes that came with my Fluke 179 though.
 

Offline nanofrog

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Re: Multimeter fuses
« Reply #45 on: January 29, 2017, 12:27:59 am »
I've just run into this dilemma, I was shocked to see the large fuse costing 1/3 the price of the meter.

There are a few threads here about this, and I posted the same request (below) in case anyone reads those old threads. Seeing such a price decrepancy made me realize the fake/clone market For these is a real concern. I'm not going to get into the debate if "similar" fuses are ok, or good enough. In my use, there are times I might rely on them, so I'd like to find the original spec'd fuses at a reasonable price, if that's even possible?

Anyone find a reputable online company, (I'm in the US) that sells both types of replacement fuses at reasonable prices? BM235 model.

I looked at both Mouser, and GreyBar, both large companies, but a single large fuse is over $40/each, and of course I can find them on eBay, for far less, but I have no idea if they are Chinese clones, since China is the source. The price range between them is crazy, 3 large fuses cost as much as the base meter. THANKS!
What are the original fuses' P/N or specifications?

I ask, as you can usually find equivalents from other manufacturers. In the case of the linked fuse ($40 something), it's price is because it's rated for 1kV AC & 1kV DC. Sadly the equivalents are similarly priced (i.e. Littlefuse 0FLU011.U or 0FLU011.T).  :(
 

Offline MacMeter

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Re: Multimeter fuses
« Reply #46 on: January 29, 2017, 12:42:20 am »
FROM THE ONLINE EEVBlob BM235 USER MANUAL:

Fuse F1 for uAmA current input: 0.4A/1000V DC/AC, IR 30kA FAST fuse or better; Dimension: 6 x 32 mm
SIBA 70-172-40 FF400mA

 
Fuse F2 for A current input: 11A/1000V DC/AC, IR 20kA F fuse or better; Dimension: 10 x 38mm?Bussman DMM-B-11A?Littelfuse FLU011
 

Offline David Hess

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Re: Multimeter fuses
« Reply #47 on: January 29, 2017, 12:47:39 am »
I wonder how well it would work to take a correctly sized glass fuse and rebuild it with sand or an appropriate filler inside.
 

Offline nanofrog

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Re: Multimeter fuses
« Reply #48 on: January 29, 2017, 01:49:45 am »
FROM THE ONLINE EEVBlob BM235 USER MANUAL:

Fuse F1 for uAmA current input: 0.4A/1000V DC/AC, IR 30kA FAST fuse or better; Dimension: 6 x 32 mm
SIBA 70-172-40 FF400mA

 
Fuse F2 for A current input: 11A/1000V DC/AC, IR 20kA F fuse or better; Dimension: 10 x 38mm?Bussman DMM-B-11A?Littelfuse FLU011
The uA/mA fuse (F1) isn't all that expensive (Galco carries the Siba 70-172-40 for $7.43).

They also carry the Littlefuse FLU011 for $32.10 (best price I've seen, but still on the expensive side IMHO).

The SIBA equivalent P/N = 5019906.11, and it's a LOT cheaper @ $8.13 from TME (they're located in Poland, but they do ship to the US).  :-+
 
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Offline mmagin

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Re: Multimeter fuses
« Reply #49 on: January 29, 2017, 01:52:57 am »
Its not merely that these fuses dissipate energy better, they also extinguish an arc better.  I have never seen a cheap fuse rated at hundreds of volts DC.
« Last Edit: January 29, 2017, 06:51:18 pm by mmagin »
 


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