Solid Fuses: Visible Indicator If Blown?

[Ralph Mowery]

Anything I use will have a CAT rating when working on any voltage above about 50 volts.

Fluke put out a film that shows what can hapen with the less expensive meters when used on equipment that can have a very high current capacity. Even putting the wrong fuse in a meter rated cat3 or more can get you in trouble. The beter meters will have a fuse in the ohm meter section. If you hapen to put the meter in the ohm or amp setting and get across a voltage source and the fuse blows, but the not rated fuses can arc over and have the effect of not blowing. In almost no time the leads insulation melts and you are across the voltage source. Or the leads explode from the excessive current.

That little Fluke T3 tester is very handy. Small enough to slip in the back pocket. They also make a T100 multimeter about the same size that works very well . It will do voltage and up to around 1000 ohms and has a provision to act like a clamp on ampmeter. It is also almost impossiable to blow up. We used them at work and would often go across fuses on 480 volt 3 phase circuits. Most often just using the ohms setting and going across fuses. Never did see one go bad even when the fuse was blown. I probably checked thousands of fuses this way on running equipment.

[Ralph Mowery]

At work there are thosands of fuses. Many of them are in holders that have neon bulbs for voltages over 100 volts and LEDs in them for the 24 volt circuits. Makes finding a bad fuse easy most of the time.

Some of the larger fuses have a set of contacts on the side that are normally open. When the fuse blows the contacts close and light up an indicator.

[bud--]

The tester also has a CAT3/CAT4 rating - a real good idea if you are testing a BFF. That means the meter won't blow up, which some non-CAT rated meters might when used on high capacity circuits.

[The Daring Dufas]

Were you in The Coast Guard? Those transmitters put out some incredible power but I seem to recall them being shut down only to wind up being considered as a backup because of the possibility of GPS being jammed or knocked out by solar flares. Heck, the government will probably wind up with some sort of system like it if GPS were to turn out to be somehow vulnerable. As tall as the towers were for LORAN-C, was lighting a big cause of the systems going down and switching to backup transmitters? o_O

TDD

[sam E]

Not amperes, current (or amperage if you insist). 'amperes' are units of measurement, and don't acutually exist in the wire.

[snip]

[DerbyDad03]

I spent a year at USCG LorSta Sylt Germany. Sylt is a resort island in the North Sea with casinos, all variety of night life and nude beaches. I paid for it with a year at USCG LorSta Port Clarence Alaska. Night life consisted of double deck Pinochle, hours upon hours of Cribbage and poker with the Eskimos when Port Clarence Bay froze over so they could cross it by snow mobile. I spent my last year as an instructor at the Loran training center on Governor's Island, NY. My home town was NYC, so they basically sent me home for my last year.

If I recall correctly, Loran stations across the globe began being shutdown in the early 90?s. Many stations went solid state and unmanned years before that. All remaining Loran C service was terminated in 2010. I don't know which, if any, Loran chains are still available as backup for GPS. I do know that some stations were dismantled and towers taken down.

Check out this video of the tower at Port Clarence.

Lightening hit our tower in Germany, basically melting the antenna coupler transformer. We were off air for a few weeks while we waited for parts to rebuild the antenna coupler and final amplifier stage of the transmitter that was on-air at the time. I don't remember how it worked, but there was some kind of system that handled most strikes without knocking us off the air. This one was just too big.

Interesting fact about the construction of Loran stations: Even though the guy wire system was designed to spin the tower basically straight down should there be a tower failure, each Loran station was built so that the closet building to the tower, other than the transmitter building of course, was no closer to the base of the tower than the tower was high. In the next-to-impossible case that the tower fell "sideways" it would miss the buildings.

Since the weather in Port Clarence was an issue, we had a 1/4? mile enclosed "hallway" from the main station to the transmitter building. No heat and very little light, but at least we were out of the weather as we walked (or biked) to the transmitter building. The inside walls were coated with ice and there were snowdrifts inside the hallway where the snow blew through the seams in the walls.

[micky]

You know, looking at it again, it could be red either way. I guess I thought you were measuring the circuit because people do sometimes and because the reading of the fuse while the fuse is in the circuit is hardly worth mentioning, once you've measured it while it's out.

[(PeteCresswell)]

Per micky:

Thanks, but, in retrospect, when I pick it apart it technically does not make sense: with the fuse out of the "Circuit" there's nothing between the probes... therefore no circuit.

[micky]

Au contraire.

"(ohmmeter shows same reading with or without fuse in circuit)"

You don't say that the reading is the reading from the circuit. It coudl be the reading from the fuse, whether it is in or out of the circuit.

[Stormin Mormon]

I might have missed it. But, what ARE the three settings? Did anyone win the gold star?

[(PeteCresswell)]

Per micky:

That's where the "...poor choice of words..." comes in.

[Stormin Mormon]

Did anyone figure out which three settings on VOM will test a fuse?

. Christopher A. Young Learn about Jesus

.

[The Daring Dufas]

Volts, Amps and Ohms. Of course for high currents it's the clamp on ammeter but lower current that won't melt your test leads it's through the DMM. An appliance that draws 2.5 amps and has a 3 amp fuse that's blown, you can measure the current by putting your test leads across the blown 3 amp fuse and if you see a 5 amp reading, you know there is a problem in the circuit. I have some small resettable circuit breakers with alligator clip test leads attached that I use for checking low current circuits which will help prevent the loss of the magic smoke which is contained in all electrical and electronic devices. Very high voltage is something you must treat with a lot more respect since it can hunt your happy butt down through many more paths. ^_^

TDD

[Stormin Mormon]

Now, that's totally helpful. Years ago, American Science And Surplus, or maybe it was Fair Radio. Someone had 5 amp circuit breakers before the Popper came into play.

One time I went to the parts house, and asked on behalf of my boss, for a five pack of 5 amp fuses. The computer said that pack cost $20.40, so I handed them back. Bought some at the auto parts.

Amping across blown fuse, that's clever.

. Christ> >> I might have missed it. But, what ARE the three settings?

[clare]

But amping across the blown fuse tells you no more about the FUSE than using a Voltmeter. It MAY tell you why the fuse blew. A simple neon circuit tester works just as good, fits in your shirt pocket. (doesn't work for low voltage circuits though)

[Stormin Mormon]

Helps determine why the fuse blew. Hmm. I guess you noticed what TDD was saying, and reflect back that information. Carry on.

. Christ>> .

[Stormin Mormon]

I guess you missed the shift. TDD changed the subject, and gave us some more infor- mation on how to do electrical testing.

BTW, thank you, TDD, that's very helpful and thoughtful.

. Christ> >

[Ralph Mowery]

Not a good idea to put an ampmeter test probes across a fuse. Chances are that if the fuse blew the current draw is much higher than the fuse is rated for. The inexpensive meters could blow in your face. The beter ones will blow their internal fuse.

If something past the fuse opens up the fuse could be good but no current would pass. If there is no power going to the fuse, you still do not know if the fuse is good or bad. Not many ampmeters will take going from the load side of the fuse to the return power wire. If they do, the fuse will most likely blow.

The ampmeter clamped across a wire is only a good test to tell that the fuse is good for sure, but not if it is bad.

The voltmeter test will tell if you have power, if so then you can go across the fuse and from the load side of the fuse to the other power wire. This will tell you if the fuse is good, bad, or no power. But not if the fuse is good or bad if you do not have any power.

[Tegger]

Stormin Mormon wrote in news:6yC%t.84852$ [e-mail]:

It is. That assertion I made about electricity traveling on the surface of wires is apparently wrong. In my searching for evidence to back up my claim, all I came up with was the opposite.

I lose the Netpick Tournament to you. Now I have to kill you.

[Tegger]

The Daring Dufas wrote in news:l1morp$h59$ [e-mail]:

That happened to my dad back in the '70s on his 1970 Ford. Somehow he managed to short the terminals on the car's 12V battery using a wrench and his metal watch band; there was a large spark, a loud snap, and the watch flew onto the driveway. I was watching when this happened.

There was a small, melted hole in the clasp of the band. The spark also melted and broke one of the pins that held the band to the clasp, which is why the band came apart. I think it was my dad's physical reaction to the shock that caused the watch to fly off his wrist and onto the driveway; I'm not sure it would have done that just from the spark alone.