Fluke could have used standard versions, but bet they did this so you have to buy their fuses.
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.
It's hard to think that the 10kA wouldn't clear the fault if the 20mm one arced over (without exploding)
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.
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...
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?
SNIPSNIP
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.
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.
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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.
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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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.
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 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.