Author Topic: Fluke 179 Multimeter Fuse  (Read 4233 times)

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Offline bostonmanTopic starter

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Fluke 179 Multimeter Fuse
« on: September 26, 2022, 03:23:23 am »
Think I accidentally blew the 440mA fuse in my Fluke 179.

These replacement ones seem costly ($7.49 on Amazon). Does anyone know where to find similar lower cost versions?
 

Online bdunham7

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Re: Fluke 179 Multimeter Fuse
« Reply #1 on: September 26, 2022, 03:40:16 am »
They're expensive and apparently commonly faked.  I believe the ones from Witonics are genuine, but I couldn't prove it.  I'd stick with a reliable supplier and live with the expense.  You can buy a 5-pack of these from TEquipment for under $30.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline bostonmanTopic starter

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Re: Fluke 179 Multimeter Fuse
« Reply #2 on: September 26, 2022, 03:44:56 am »
I hadn't considered fake ones, but this is good to keep in mind.

You're correct on not chancing cheaper priced ones that could be fake because one can save a few bucks, but end up blowing an expensive meter.

Fluke could have used standard versions, but bet they did this so you have to buy their fuses.
 

Online bdunham7

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Re: Fluke 179 Multimeter Fuse
« Reply #3 on: September 26, 2022, 04:04:33 am »
Fluke could have used standard versions, but bet they did this so you have to buy their fuses.

No, they did that to meet safety requirements and prevent you from turning yourself into ash when you accidentally short out an industrial service panel with your meter because you left the leads in the current sockets.  Look at the interrupt ratings on those fuses--the small one can interrupt a fault current of 10,000 amps.

Edit:  Case in point...

https://www.ecmweb.com/safety/arc-flash/article/20898038/the-case-of-the-deadly-arc-flash
« Last Edit: September 26, 2022, 04:18:56 am by bdunham7 »
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Offline Black Phoenix

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Re: Fluke 179 Multimeter Fuse
« Reply #4 on: September 26, 2022, 11:10:31 am »
Exactly. There is a reason why such fuses are used, not because it is what a brand wants to milk money from the consumer.

Case and point other brands of equipment that are certified for such work and have the proper international safety certifications use same kind of fuses or of similar construction.

Normally I bash Fluke because of their price practices, lack of innovation and "milking" 20+ year old designs with minor updates (87 series for example) but in terms of safety they are second to none, together with other brands as Brymen, Hioki, Amprobe, Gossen Metrawatt and Kyoritsu.
« Last Edit: September 26, 2022, 04:17:22 pm by Black Phoenix »
 
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Offline bostonmanTopic starter

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Re: Fluke 179 Multimeter Fuse
« Reply #5 on: September 26, 2022, 12:36:54 pm »
I indirectly owe Fluke an apology then for accusing them of trying to have an edge on replacement fuses.

I haven't opened the meter yet to measure the fuse as I'm avoiding to open it, close it, open it again, and then close it. Most likely I accidentally touched the two leads when measuring current. The connector I needed to connect to was a tiny Molex or whatever, so i used staples as pins to clip onto, but, in the process of moving around, the staples turned and must have touched; thus blowing the fuse.

Sadly, I didn't even need to measure current, but was just curious about how much the device was drawing.

Thanks for the feedback - I'll plan to spend the extra few dollars instead of searching for cheaper ones that could end up being a knock off.
 

Offline unknownparticle

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Re: Fluke 179 Multimeter Fuse
« Reply #6 on: September 26, 2022, 02:30:37 pm »
Basically, don't buy off ebay or even Amazon, particularly if the seller admits to being located in China.  There are more fake sources than genuine.
There is a youtube vid, probably more than one actually, but the one I saw dismantled a fake and a genuine fuse to reveal the difference. The fake was utter cr4p, the genuine very impressive.
DC coupling is the devils work!!
 

Online Gyro

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Re: Fluke 179 Multimeter Fuse
« Reply #7 on: September 26, 2022, 07:41:18 pm »
It's a shame Fluke abandonded the dual fuse approach that they used on the old Fluke 25 / 27. They had a small 20mm 630mA 250V ceramic fuse, with a big 3A 10kA fuse in series to clear any high energy fault that the little one couldn't. In most cases, the little 20mm fuse would clear the fault, leaving the expensive one intact.

The 10A range was still a single 10kA fuse - 15A in those days but the shunt was bigger and higher thermal mass.
« Last Edit: September 26, 2022, 07:47:24 pm by Gyro »
Best Regards, Chris
 
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Online bdunham7

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Re: Fluke 179 Multimeter Fuse
« Reply #8 on: September 26, 2022, 07:52:56 pm »
It's a shame Fluke abandonded the dual fuse approach that they used on the old Fluke 25 / 27. They had a small 20mm 630mA 250V ceramic fuse, with a big 3A 10kA fuse in series to clear any high energy fault that the little one couldn't. In most cases, the little 20mm fuse would clear the fault, leaving the expensive one intact.

That was a handy setup, also found on the 8840A/8842A series, but you might notice that no meter with that setup has a CAT rating (AFAIK).  Even the later CAT-III/1000V 27 has abandoned the dual fuse setup, so perhaps there's a valid reason.  I simply use an external fused 1R shunt setup I made when I'm doing something like measuring a small current in a device powered by a large source--like a car battery.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Online Gyro

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Re: Fluke 179 Multimeter Fuse
« Reply #9 on: September 26, 2022, 08:05:39 pm »
Yes, hard to say, they were pre-Cat rating and they had abandoned the approach generally by the time the later 27 had come along. I found an original ad for the early 25/27 which said they have 6kV surge rating at 600V which I suppose would have made them CAT III 600V (the main fuses were 600V too). It's hard to think that the 10kA wouldn't clear the fault if the 20mm one arced over (without exploding) [Edit: just as you would expect it to blow before the mA shunt clamp diodes], they presumably tested it thoroughly as they were Mil spec and MSHA mine certified. I really don't know though.

Yes, I usually use external shunts for miniumum burden too, I have quite a collection.
« Last Edit: September 26, 2022, 08:13:56 pm by Gyro »
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Online bdunham7

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Re: Fluke 179 Multimeter Fuse
« Reply #10 on: September 26, 2022, 08:28:55 pm »
It's hard to think that the 10kA wouldn't clear the fault if the 20mm one arced over (without exploding)

I've always thought it was a good design and I've never heard of an issue, but I wonder what would happen if you connected it to a 1000VDC @ 3A source--that would arc over the little fuse indefinitely but the 3A wouldn't blow the big one.  That's a corner case that is resolved by simplifying the product, easy to sell to management. 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Online Gyro

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Re: Fluke 179 Multimeter Fuse
« Reply #11 on: September 26, 2022, 08:36:06 pm »
Yes, I suppose it was an easy sell, especially when they were using single main board space rather than the seperate vertical fuse board.


P.S. I recently acquired a decent Fluke 25 with both main fuses blown. Some *** had blown the 15A fuse and then put the 3A fuse in its place and blown that too. The 20mm fuse was of course intact. ::)
« Last Edit: September 26, 2022, 08:40:06 pm by Gyro »
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Offline Black Phoenix

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Re: Fluke 179 Multimeter Fuse
« Reply #12 on: September 27, 2022, 02:24:54 am »
It's a shame Fluke abandonded the dual fuse approach that they used on the old Fluke 25 / 27. They had a small 20mm 630mA 250V ceramic fuse, with a big 3A 10kA fuse in series to clear any high energy fault that the little one couldn't. In most cases, the little 20mm fuse would clear the fault, leaving the expensive one intact.

The 10A range was still a single 10kA fuse - 15A in those days but the shunt was bigger and higher thermal mass.

What's the problem of the fuse doing their function, ie, blowing up? Why the old design was better than the newer design? How regularly you blow up fuses?

In 15 years I've been using DMMs I blow up 1 fuse at total. That's what 30 euros in 15 years. That's one less coffee I drink per year.

The fuse function is to protect the operator in case of a fault. It's a consumable. Same as the DMM. If you blow up the fuse or the DMM you can buy a new one. I didn't see extra lives to be sold anywhere as in games...
 

Offline james_s

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Re: Fluke 179 Multimeter Fuse
« Reply #13 on: September 27, 2022, 02:32:35 am »
It's a shame Fluke abandonded the dual fuse approach that they used on the old Fluke 25 / 27. They had a small 20mm 630mA 250V ceramic fuse, with a big 3A 10kA fuse in series to clear any high energy fault that the little one couldn't. In most cases, the little 20mm fuse would clear the fault, leaving the expensive one intact.

The 10A range was still a single 10kA fuse - 15A in those days but the shunt was bigger and higher thermal mass.

What's the problem of the fuse doing their function, ie, blowing up? Why the old design was better than the newer design? How regularly you blow up fuses?

In 15 years I've been using DMMs I blow up 1 fuse at total. That's what 30 euros in 15 years. That's one less coffee I drink per year.

The fuse function is to protect the operator in case of a fault. It's a consumable. Same as the DMM. If you blow up the fuse or the DMM you can buy a new one. I didn't see extra lives to be sold anywhere as in games...

The only thing wrong is the price. I can see the value in having both a cheap fuse and an expensive fuse in series, with the cheap fuse likely to blow in the sort of casual mistakes that happen sometimes while the expensive fuse is still there to save you from a catastrophic mistake. It's true that one normally doesn't blow fuses very often but it does happen once in a while, and it's annoying when it happens and you haven't got a spare on hand.
 

Offline robert.rozee

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Re: Fluke 179 Multimeter Fuse
« Reply #14 on: September 27, 2022, 03:06:12 am »
What's the problem of the fuse doing their function, ie, blowing up? Why the old design was better than the newer design? How regularly you blow up fuses?

the answers lie in the following case:
https://www.ecmweb.com/safety/arc-flash/article/20898038/the-case-of-the-deadly-arc-flash

the fuse needs to not only 'blow', but also interrupt the current flow prior to any mechanical rupturing. once 'blown', you do NOT want the fuse and body to be replaced with a  glowing ball of highly-conductive plasma. the large fuses you see in fluke (and other) meters are filled with sand around the fuse element, and are enclosed in an explosion-proof fibrous body that can contain the contents long enough for any plasma to cool down. they are a quite high-tech device, far more than just a bit of fuse wire.

the above link is why i only use fluke meters on mains (230v here) and higher voltages. it only takes one accident to be removed from the gene pool!


cheers,
rob   :-)
 
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Offline Black Phoenix

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Re: Fluke 179 Multimeter Fuse
« Reply #15 on: September 27, 2022, 03:25:44 am »
SNIP
SNIP

Rob, thanks for your reply but you didn't understood my question.

As I stated here:
Exactly. There is a reason why such fuses are used, not because it is what a brand wants to milk money from the consumer.

Case and point other brands of equipment that are certified for such work and have the proper international safety certifications use same kind of fuses or of similar construction.

Normally I bash Fluke because of their price practices, lack of innovation and "milking" 20+ year old designs with minor updates (87 series for example) but in terms of safety they are second to none, together with other brands as Brymen, Hioki, Amprobe, Gossen Metrawatt and Kyoritsu.

I said the same as you, but with different words.

My question is aimed at Gyro who states that the old design of double fuse (one glass and one big one in series) was preferable to him because of the fact that it would not blow the big one most of the times, so saving money and the hassle of replacing it.

That's why I asked what I asked. Other than cost related (that still as I said I don't see as a minus since I blown one fuse in 15 years) I don't understand why such design in his idea is preferable to the current one.
 

Offline james_s

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Re: Fluke 179 Multimeter Fuse
« Reply #16 on: September 27, 2022, 03:45:08 am »
That's why I asked what I asked. Other than cost related (that still as I said I don't see as a minus since I blown one fuse in 15 years) I don't understand why such design in his idea is preferable to the current one.

It's exactly cost, because not everyone is as careful as you. I don't blow them very often but I have blown them, especially back before I had a clamp probe. It depends on what you're doing, with some use cases it's a lot easier to blow the fuse than others.
 

Offline Black Phoenix

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Re: Fluke 179 Multimeter Fuse
« Reply #17 on: September 27, 2022, 04:39:06 am »
It's exactly cost, because not everyone is as careful as you. I don't blow them very often but I have blown them, especially back before I had a clamp probe.

Not careful, more like I rarely use the amp function in my DMMs and when I use it is mostly low amp applications. When I need to use on expected to be higher amps I use a clamp probe.

But yes, I understand your reasoning and agree with it.
 

Online Gyro

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Re: Fluke 179 Multimeter Fuse
« Reply #18 on: September 27, 2022, 09:22:45 am »
...
My question is aimed at Gyro who states that the old design of double fuse (one glass and one big one in series) was preferable to him because of the fact that it would not blow the big one most of the times, so saving money and the hassle of replacing it.

That's why I asked what I asked. Other than cost related (that still as I said I don't see as a minus since I blown one fuse in 15 years) I don't understand why such design in his idea is preferable to the current one.

Firstly, please note that nowhere did I mention "glass" fuses. The use of a low breaking capacity physically fragile glass fuse would be patently ridiculous in a serious meter safety setting.

My point was simply that Fluke used the double fuse approach to avoid blowing the large and expensive 10kA breaking capacity mA fuse, designed to clear faults in CAT III / IV situations, due to a silly mistake (eg. forgetting a large capacitor inrush, or forgetting the jacks) in a Cat I environment, you might almost say wasteful. It's not something I make a habit of (I haven't blown one for years, but I'm retired now) but people tend to be a little less cautious on the bench than situations where they may receive an arc flash in the face! Having blown such a fuse, you are duty bound to replace it with a suitable replacement to maintain the integrity of the meter. Unfortunately this leads to delay (unless in a lab with spares stock), frustration , and of course cost - hence the flourishing market in fake fuses . Even in a large development lab, I remember the gentle ridicule and teasing that people suffered when going for a replacement meter fuse (one step down from having to tell the calibration dept that you had wrapped the needle on your AVO or blown the 50R terminator on your scope!). At least one member on here has admitted to bridging the fuse with a thin strand of wire, and you too frequently hear of examples of test equipment where this has happened - my 25 was probably one step away from that fate when I got it, with both 10kA fuses already blown.

At some point, somebody at Fluke said 'let's not do that any more' and we will never know why. As I mentioned previously they did it on their most rugged DMM, with all sort of certifications, which was marketed for many years. They must have done extensive testing of the safety of the dual fuse approach. Apart from the corner case that bdunham7 mentioned (which I suspect would actually be sucessfully quenched by the 20mm fuse), there are many internal parts that rely on the 10kA fuse to safely clear a fault in CAT II+ environments including PCB traces, clamping diodes, switch contacts etc. This would all have been tested.

I would love to see Joe Smith put a Fluke 25 / 27 through it's paces, I think the closest he has come is the Fluke 77, but that used spark gaps rather than 5 MOVs. Even then, he does not have the capability to test high current fault clearing. It would probably be one for Photoinduction! :scared: Comprehensive testing would require a large pile of expensive fuses anyway.

As I mentioned, I also rarely use meter current ranges (none of my bench meters even have them), but I felt duty bound to replace the fuses with genuine items anyway (again, to maintain the integrity of the meter). I have a bunch of shunts, ranging from 1k (1mA) up to 150A. These of course are only suitable for CAT 1 lab bench environment (maybe occasionally CAT II in a UK fused plug environment). Current clamp probes are a godsend for AC in higher CAT environments, much less satisfactory for measuring low DC leakage currents in the same situation.
« Last Edit: September 27, 2022, 09:45:36 am by Gyro »
Best Regards, Chris
 

Online Gyro

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Re: Fluke 179 Multimeter Fuse
« Reply #19 on: September 27, 2022, 10:18:14 am »
What's the problem of the fuse doing their function, ie, blowing up? Why the old design was better than the newer design? How regularly you blow up fuses?

the answers lie in the following case:
https://www.ecmweb.com/safety/arc-flash/article/20898038/the-case-of-the-deadly-arc-flash

the fuse needs to not only 'blow', but also interrupt the current flow prior to any mechanical rupturing. once 'blown', you do NOT want the fuse and body to be replaced with a  glowing ball of highly-conductive plasma. the large fuses you see in fluke (and other) meters are filled with sand around the fuse element, and are enclosed in an explosion-proof fibrous body that can contain the contents long enough for any plasma to cool down. they are a quite high-tech device, far more than just a bit of fuse wire.

the above link is why i only use fluke meters on mains (230v here) and higher voltages. it only takes one accident to be removed from the gene pool!


cheers,
rob   :-)

That accident happened because the meter was a fake. Wrong PCB clearances, little glass fuse, untested against specification. It's markings and specifications were false. It should never have been where it was. Sad and sickening like all arc flash incidents but not relevant to the Fluke discussion.

In the fluke case, the 10kA fuse would have taken on the fault clearance as soon as the current rose significantly above 3A. 20mm Ceramic fuses (also sand filled) typically have an interrupt rating of 1.5kA @250V on their own.
« Last Edit: September 27, 2022, 10:37:36 am by Gyro »
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Offline Black Phoenix

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Re: Fluke 179 Multimeter Fuse
« Reply #20 on: September 27, 2022, 11:23:29 am »
...
My question is aimed at Gyro who states that the old design of double fuse (one glass and one big one in series) was preferable to him because of the fact that it would not blow the big one most of the times, so saving money and the hassle of replacing it.

That's why I asked what I asked. Other than cost related (that still as I said I don't see as a minus since I blown one fuse in 15 years) I don't understand why such design in his idea is preferable to the current one.

Firstly, please note that nowhere did I mention "glass" fuses. The use of a low breaking capacity physically fragile glass fuse would be patently ridiculous in a serious meter safety setting.

My mistake sorry. And as I also said to James, I understand the situation at hand and agreed.

In such use you demonstrated, yes it would be logical the double fuse in series logic. Sorry for calling the wrong fuse type.

Now it would be good to know why Fluke changed that approach. I remember coming around a topic where the OP was a Fluke employee and was in the design/engineering team responsible for DMMs. It would be good to have his input in case he could shed some light about this.
« Last Edit: September 27, 2022, 11:26:52 am by Black Phoenix »
 

Online Gyro

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Re: Fluke 179 Multimeter Fuse
« Reply #21 on: September 27, 2022, 11:40:42 am »
No problem.  :)

It's one of those problems where your instinct says the approach should work but you don't know why they abandoned it, and there's no sensible way of testing it. It certainly wouldn't work with a 35A interrupt glass fuse, but the ceramic has a considerable interrupt rating of its own, way above what would be needed to bring the 10kA interrupt fuse into the game.

That would indeed be a thread worth finding (I think I remember the thread you're talking about now). Irrc, he was responsible for the very early Fluke designs (the ones with the row of buttons down the side - 8060), pre 25 and 8840, but may have some insight.


EDIT: Found it... https://www.eevblog.com/forum/testgear/old-fluke-multimeters/   It looks as if drtaylor was still active here in March.

EDIT 1: Another twist. Looking at the 8060 manual, it (and, from the above thread, the 8020) also included two series fuses, a user replaceable 20mm / 1" 2A 250V and a service replaceable 600V 3A 10kA one. The plot thickens.
« Last Edit: September 27, 2022, 12:20:47 pm by Gyro »
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Online bdunham7

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Re: Fluke 179 Multimeter Fuse
« Reply #22 on: September 27, 2022, 01:58:35 pm »
That accident happened because the meter was a fake. Wrong PCB clearances, little glass fuse, untested against specification. It's markings and specifications were false. It should never have been where it was. Sad and sickening like all arc flash incidents but not relevant to the Fluke discussion.

In the fluke case, the 10kA fuse would have taken on the fault clearance as soon as the current rose significantly above 3A. 20mm Ceramic fuses (also sand filled) typically have an interrupt rating of 1.5kA @250V on their own.

Actually the situation there was a bit different.  The meter wasn't 'fake', and it didn't have any ratings at all IIRC.  It was simply a primitive model and thus didn't comply with any modern standards, even though it was manufactured more recently when those standards were, well, standard--but not mandated.  The case against the manufacturer was simply that they had designated it as an "industrial" model.  More importantly to this discussion, the electrician was measuring voltage, not current, and there's no allegation that he connected the meter improperly.  That particular meter used a fuse in the voltage circuit--to protect the meter, not the user--as do some other analog meters from previous eras.  I believe even some Simpson VOMs are like this, although I don't know what brand was involved here.  I would never use something like my Simpson 270 on a high-energy 3-phase panel!  In the case of a modern Fluke, there would not have been any blown fuses and the meter would presumably withstand whatever transient was on the mains, probably without damage--although we don't actually know how powerful that surge was.
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Offline robert.rozee

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Re: Fluke 179 Multimeter Fuse
« Reply #23 on: September 27, 2022, 02:30:35 pm »
[...]
the answers lie in the following case:
https://www.ecmweb.com/safety/arc-flash/article/20898038/the-case-of-the-deadly-arc-flash
[...]

That accident happened because the meter was a fake. Wrong PCB clearances, little glass fuse, untested against specification. It's markings and specifications were false. It should never have been where it was. Sad and sickening like all arc flash incidents but not relevant to the Fluke discussion.

In the fluke case, the 10kA fuse would have taken on the fault clearance as soon as the current rose significantly above 3A. 20mm Ceramic fuses (also sand filled) typically have an interrupt rating of 1.5kA @250V on their own.

the meter (in the linked article) was not a "fake", it was just badly designed. while it did not have a IEC 600V CAT III rating (as would be required for the job it was performing), neither did it make any claims that it did have such a rating. its main legal sins were claiming to be an "industrial multimeter" (a meaningless term) and having a scale on the analog face with markings going up to 1000v. these were sufficient to fool the victims into feeling a false sense of safety.


given a multimeter has a small 'sacrificial' fuse in series with a 10kA fuse (ie, early fluke), there is risk that a fault condition could knock out the sacrificial fuse in such a way that a plasma ball can form within the meter housing. at that point, the 10kA fuse is unlikely to even still be in the path of current flow, and the destruction of the meter will be well underway; as the linked article says, "the victims' fates were sealed".

if, on the other hand, you JUST have the 10kA fuse in line, it will blow, in theory containing any plasma within the fuse housing until it has been safely extinguished. this may end in the fuse rupturing, and the insides of the meter being destroyed. but the meter and fuse will have fulfilled their job - containing everything within the meter's housing.

note that the multimeters are (or at least should be) designed to be destroyed under certain fault conditions, but still contain damage to within the meter's housing and leave the user unharmed. the multimeter is itself a 'sacrificial' device.


cheers,
rob   :-)
 

Online Gyro

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Re: Fluke 179 Multimeter Fuse
« Reply #24 on: September 27, 2022, 05:40:43 pm »
the meter (in the linked article) was not a "fake", it was just badly designed. while it did not have a IEC 600V CAT III rating (as would be required for the job it was performing), neither did it make any claims that it did have such a rating. its main legal sins were claiming to be an "industrial multimeter" (a meaningless term) and having a scale on the analog face with markings going up to 1000v. these were sufficient to fool the victims into feeling a false sense of safety.

I stand corrected. Not having details of the meter or it's front panel markings it's hard to judge how clear the telltail signs would have been, it clearly wasn't suitably CAT rated but there's no telling how obvious this would have been. There's a lesson in there about borrowed equipment and another huge one from the photo of the probe with remains of an alligator clip! Regardless of the rating of the meter, anything other than proper protective shrouds, exposing just a couple of mm of tip, on the test probes would have immediately de-rated them to CAT II at any voltage - that was easily enough to have been the direct cause such an accident on its own. The other slight inconsistency is that, from the description, the electrician was  already measuring voltages when the arc flash occured so the (totally inadequate) fuse probably wasn't actually in circuit at the time but that's irrelevant in the scheme of things. 1000V on the scale shouldn't have been enough to fool the individuals on its own (there aren't many meters without a 1kV range) the term 'industrial' is tricky It's the sort of labelling that rings warning bells. As with most of these cases, there are a bunch of contributing factors - I always find such pictures distressing.

Quote
given a multimeter has a small 'sacrificial' fuse in series with a 10kA fuse (ie, early fluke), there is risk that a fault condition could knock out the sacrificial fuse in such a way that a plasma ball can form within the meter housing. at that point, the 10kA fuse is unlikely to even still be in the path of current flow, and the destruction of the meter will be well underway; as the linked article says, "the victims' fates were sealed".

if, on the other hand, you JUST have the 10kA fuse in line, it will blow, in theory containing any plasma within the fuse housing until it has been safely extinguished. this may end in the fuse rupturing, and the insides of the meter being destroyed. but the meter and fuse will have fulfilled their job - containing everything within the meter's housing.

note that the multimeters are (or at least should be) designed to be destroyed under certain fault conditions, but still contain damage to within the meter's housing and leave the user unharmed. the multimeter is itself a 'sacrificial' device.

Therein lies the question. I suppose it would be easy to substitute a piece of copper rod for the 20mm fuse but it does seem counterintuitive. It hinges on the amount of testing that Fluke carried out... and on the rise time of the fault current. The 10kA is a maximum permissible quench current, the large fuse ought to be able to clear the fault long before that. There is a case for it in CAT II conditions though.

Yes certainly, the construction of the case is an integral part of the protection, its internal blast shield moldings, the depth of the case flanges and the ultimate impact strength of the case material are all key. Everything is ultimately sacrificial apart from the user.
« Last Edit: September 27, 2022, 05:48:03 pm by Gyro »
Best Regards, Chris
 


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