Solid Fuses: Visible Indicator If Blown?

I used a good old Wiggy for years when doing a lot of electrical work and I'm sure I could find it in my stuff if I haven't lost it. The Fluke T3 is a modern variation which looks like the old Wiggy.

TDD

That's going to keep me awake, wondering. I hope you give the answer, eventually. After the suitable amount of begging, of course.

. Christ>

I figure one would be volts, measure the voltage drop across the fuse. Open fuse, would show line voltage. Active fuse would show a voltage drop of 1 or 2.

Ammeter might show current flow through the fuse. Open fuse would read zero amps.

If the circuit is turned off, tagged and locked, the ohms scale can be used, maybe. Depending on some of the other circuits and wires involved.

And by now, I've had to replace three meters cause I'm all wrong. Let out the little white smoke from my meters.

. Christ> The Daring Dufas wrote in

How would capacitance (farads) test a diode?

The cheap VOM I've got from HF, test volts AC, volts DC, miliamps DC, amps DC.

Good VOM might include farads, diode, AC amps.

A few generations from now, we'll test dilithium crystals for the warp drive.

. Christ> Dean Hoffman > wrote:

If memory serves, you're going to tell us which three settings on a DMM. One is volts, other is ohms. What's the third?

The other guy's diode tester might be similar to continuity scale I've seen now and again. Activates a high pitch beeper if continuity is found. Which is nice if you don't want to look at the scale. And if you can hear the beeper.

. Christ>>>>

I had fuses like in some surplus gear that had a panel mount fuse holder equipped with a clear cap having a bubble in it that the plunger popped up into when the fuse blew. The little tips of the plungers on some of the fuses were painted red so they would show up more easily in the bubble but it was easy to tell if the unpainted tips were in the bubble window of the cap too. I suppose that little fuse would work in a fuse holder that had an electrical contact to turn on an indicator light. I had some fuses under the dash in my van that had a tiny LED which would light if the fuse blew. ^_^

TDD

The Daring Dufas wrote in news:l1mip7$hfc$ snipped-for-privacy@dont-email.me:

Or if it's an industrial environment where equipment may need to be kept running unless absolutely necessary...

Zero volts DROP, you mean? In other words, that /all/ the voltage is going through the fuse, and /none/ through your DMM, which is supposed to have a higher impedance than the fuse has?

If the fuse was blown, then the DMM would present the lower-impedance path, and you'd see all the voltage traveling through the DMM?

Your work life is more complicated than mine. I don't have to worry about shutting down either wrong or interconnected stuff. Most importantly, I won't shut down the computer used to issue my pay check.

Light fuses sounds good. Since the fuse blows, and you likely still hvae

. Christ>

Since we're splitting hairs, and using italics, I'll add a netpick. Voltage doesn't travel through wires, amperes do.

. Christ>

Stormin Mormon wrote in news:fuB%t.126116$ snipped-for-privacy@fx01.iad:

I can netpick as well as anybody else here: Current travels ON wires, not THROUGH them.

(You'll notice I've avoided the use of italics in favor of upper case; I typed those words LOUDER than the others.)

That could cause a serious GRONK! if it's up and running when you killed the power. It's a bad idea to pull a big fuse out of an energized panel unless it's in a safety switch which won't open while turned on but the incoming line can be hot so there is still a bit of danger but if the safety switch is wired correctly there won't be any voltage on the fuses so yank away. Oh yea, trust no one, always check to make sure there is NO voltage. I've worked on industrial, commercial, government and residential electrical systems that had high, medium and low voltage power. I'm still here because I never became complacent around electricity. I'll never forget the time my brother was burned while working on a tractor. His metal watch band shorted to ground on the tractor's 6 volt starter and lit up. If I wear a watch it's always plastic. Never, ever believe that low voltage can't hurt you. ^_^

TDD

RF voltage travels on the surface too. ^_^

TDD

You're trying to claim what exactly? That the current density inside a wire is zero? In my world, it's correct to say current travels through wires. Unless you're dealing with high frequencies, where the skin effect becomes of significance.

And Daring's statement was accurate as stated, at least with regard to what you're objecting to:

"First I check for voltage on either end of a fuse to ground then across the fuse, a good fuse should measure zero volts across it "

I can see raising issue with something that isn't clear or correct. But raising spurious issues that just confuse the correct answer is pointless. If there is anything that is wrong with the statement, it's that it should say a good fuse will measure "near zero volts" across it when it's in an energized circuit. A bad one will have typically have a large amount of voltage across it with the circuit powered. Example, take a 100W light bulb in a 120V circuit with a 5 amp fuse. Fuse OK, it will read very close to zero volts across the fuse. Fuse blown, it will read ~120V. The impedance of the meter, how the current splits between the meter and the circuit, etc is just noise, unless it's some very unusual circuit where the impedance of a typical VOM is going to matter because it's of significance compared to the circuit.

" snipped-for-privacy@optonline.net" wrote in news: snipped-for-privacy@googlegroups.com:

You stay out of this. I have him on the ropes; my next move will finish him off cleanly, and I alone will claim the Netpick Trophy..

I'd be curious if you have any web sites that explain this. It seems counter intuitive.

Years ago, friends told me that microwave ovens heat food from the inside out, which is also counter intuitive. I'd ought have tested it by put in a box of frozen solid ice cream. Give it

. Christ> Stormin Mormon wrote in

Per micky:

Poor choice of words on my part. That's what I was doing: measuring the fuse.

Is it permitted, to admit mistayk on Usenet? I thought you were supposed to flame?

. Christ> Per micky:

Have you ever seen a motorized circuit breaker controlled by a 3-strike relay? We had them in the LORAN-C transmitters I used to work on. These transmitters were subject to the random arc which would trip the high voltage breaker in the power supply.

Picture a large circuit breaker above a motor with a shaft the rose out of the top. When the motor was energized, the shaft pushed the breaker handle up, energizing the high voltage Power Supply. (25K VDC max, steady state at

Controlling the motor circuit was a mechanized relay with a timer and a cam that opened and closed the relay contacts. If the transmitter arced and tripped the breaker, the cam would rotate 1 position, start a 30 second timer and power up the motor which would close the circuit breaker. If 30 seconds went by with no more arcs, the relay cam would rotate back to its "normal" position and wait patiently for the next arc. If another arc occurred within those 30 seconds, the cam would rotate one more position, power up the motor, close the breaker and once again wait for another arc. If, within the original 30 seconds a 3rd arc occurred, the cam would rotate one more position and shut down the power supply.

At that point, if everything else was working properly, other circuitry would automatically power up the standby transmitter and switch the antenna coupler to the standby unit, putting us back on air in under a minute.