Test Equipment Anonymous (TEA) : Discussion and Group Therapy Thread

[mansaxel]

I've seen very high value (100A plus) fuses filled with sand (or something). I assumed it was there for quenching. When it blows you want it to stop conducting, not to continue as an arc.

Diazed fuses (Siemens invention from the early 1900s) as used in Sweden and Germany (Among many other places!)
are sand filled, down to the household sizes of 6,10,16 A.



Most domestic fuse panels in Sweden have D II fuses.



These days, they're being installed only in select places. Most domestic uses have replaced them with DIN rail mounted MCBen.

[AVGresponding]

All modern HRC fuses have some sort of filler for arc quenching. It shouldn't be sand: https://www.electricaltechnology.org/20 ... types.html

[Zenith]

Some of the old UK power circuit fuses had the wire running through an asbestos tube. I've also seen asbestos used around the fuse in some domestic radios.

[Robert]

The granualar material in high rupture current fuses isn't so much for arc quenching (stopping conduction) as energy absortion to stop the fuse physically exploding. It presents a large surface area to the hot expanding gases cooling them and reducing internal pressures.

[AVGresponding]

It quenches the arc by removing heat, and also there's a chemical reaction making the metal-filler fused product highly resistive.

[Zenith]

All modern HRC fuses have some sort of filler for arc quenching. It shouldn't be sand: https://www.electricaltechnology.org/20 ... types.html

They mention a number of fillers in articles about HRC fuses; silica (purified sand), marble (calcium carbonate), Plaster of Paris (calcium sulphate). The wire is made of silver (which must be for good reason) and they talk about the metal vapour reacting with the filler to create an insulating compound. No doubt the other effects mentioned are also taking place.

There must have been a lot of R&D done on getting these right.

[mnementh]

trace fuse 2.jpg

trace fuse 1.jpg

Meanwhile, on the other end of the spectrum...

mnem

[25 CPS]

I guess it's hard to find good technicians whether it's a paid or volunteer environment.

Somebody needs to train them.
If that isn't possible then have supervision.
If that isn't possible (e.g. voluntary organisation) then at least have three people working alongside each other, so that there is a better chance someone will stay "wait a minute". ("alongside" != at other end of cable).

Over here we used to have apprenticeships, where companies trained school leavers before they employed them. That was possible when it was less likely people would be "stolen" by another company and/or move to a different town.

Apprenticeships exist here too, mainly in the skilled trades but do appear elsewhere too, and work placements for college and university students are common.

The guy who destroyed my clamp meter is a full blown EE with decades of experience, both in industry and at that railway museum. This is why I keep harping on the carelessness.

As for the others, you can't train common sense, work ethic, or that sort of thing. Eventually people have to stand on their own two feet but not everyone can to the same extent but, far worse, are the malicious ones that slack off or deliberately damage things. I haven't encountered the latter in volunteer situations much though. The lazy factor tends to rule out volunteer work.

Anyways, I ordered a replacement U1213A yesterday. Hopefully it checks out alright when it arrives.

[Zenith]

The guy who destroyed my clamp meter is a full blown EE with decades of experience, both in industry and at that railway museum. This is why I keep harping on the carelessness.

Some people seem accident prone, others just can't treat things properly. I had a friend who couldn't have a camera for more than about a year, because he dropped them or wrecked them some other way. They weren't cheap ones, they were Nikon etc. He got through half a dozen and he didn't use them that much. It never seemed to dawn that they were expensive things and needed reasonable care. I lent a corded hedge trimmer to another friend. He managed to cut through the cable. Some people are notorious for abusing tools, even expensive ones. It doesn't seem to have that much to do with intelligence or training.

I had a builder to do some work on the chimney. He hired a scaffold tower. I asked him why he hired them, since it was a thing he'd use all the time. He said if you hired one, it would be complete with no missing or damaged bits. If he bought one, people would ask to borrow it and it was hard to refuse, and it would often come back with parts bent or lost. It was too much hassle to buy one. Tool hire companies were geared up to deal with scaffolding towers returned with lost or broken parts.

[tggzzz]

As for the others, you can't train common sense, work ethic, or that sort of thing. Eventually people have to stand on their own two feet but not everyone can to the same extent but, far worse, are the malicious ones that slack off or deliberately damage things.

Arguably even worse are the well-meaning people that know just enough to be ingeniously dangerous.

In my first job I encountered such a person, who was universally known as "bigfoot". Glider (and no doubt other) instructors are especially wary of "Bloggs" who are approaching solo standard, since they get into situations that gently become subtly dangerous. When the instructors are being tested (annually), the testers mimic such Bloggs in order to see the instructor does take control.

[Robert]

Apprenticeships:
These are still offered by my employer and have been for over 100 years. The current chief engineer is an ex apprentice and has been with the company for 40 years....

Scaffold towers.
Renting these also means that they have an up to date inspection tag which removes another administrative chore.