Fuse: fast blown vs slow blown

"Man-wai Chang"

" The quick brown fox jumps over the lazy dog "

Think about it ...........

.... Phil

you!

=B4=E4=BA=A4! =E4=B8=8D=E6=89=93=E4=BA=A4! =E4=B8=8D=E6=89=93=E5=8A=AB! =E4= =B8=8D=E8=87=AA=E6=AE=BA! =E8=AB=8B=E8=80=83=E6=85=AE=E7=B6=9C=E6=8F=B4 (CS= SA):

The danger, on a scale from 1 to 10 is 8. Some equipment can be damaged in a millisecond, so a slow-blown fuse can result in a ruined piece of equipment. For example, an integrated circuit could need 12 volts, but you plug in the wrong wall wart that has no labels on it. It has 18 volts instead of 12 volts, but it uses the same diameter coaxial connector. A fast fuse protects in 400 microseconds, but the slow blow does not blow that fast so the 45 nanometer digital device gets melted in 1000 microseconds.

"Globemaker"

The danger, on a scale from 1 to 10 is 8. Some equipment can be damaged in a millisecond, so a slow-blown fuse can result in a ruined piece of equipment. For example, an integrated circuit could need 12 volts, but you plug in the wrong wall wart that has no labels on it. It has 18 volts instead of 12 volts, but it uses the same diameter coaxial connector. A fast fuse protects in 400 microseconds, but the slow blow does not blow that fast so the 45 nanometer digital device gets melted in 1000 microseconds.

And he has pointy ears too.

Beam me up Scotty ........

... Phil

It depends entirely on the equipment. Slow-blow fuses used to be more expensive than fast-blow fuses, and tend to be less available. So a designer's knee-jerk reaction may be to specify a fast-blow fuse 'because it's there'.

So there's a good chance that you can drop your slow-blow fuse in there and everything will be fine, but if you do and burn something up, don't come crying to me. I would hesitate to do so myself unless I knew what was in the product, and felt that a slow-blow would work OK. I would also hesitate to replace the fuse unless I knew why the original had blown -- fuses blow for reasons, and if the equipment is dorked and blowing fuses, then putting in more fuses will just make it more dorked.

Your best bet is to get the right fuse, and at least try to fix the fault before you turn the equipment on with your shiny new fuse.

For a multimeter, is it always better to use a fast blow fuse?

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Is the 13A BS1362 fuse a fast blow one?

-- @~@ Might, Courage, Vision, SINCERITY. / v \ Simplicity is Beauty! May the Force and farces be with you! /( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.39 ^ ^ 23:56:02 up 6 days 8:58 0 users load average: 1.05 1.09 1.06 ???! ???! ???! ???! ???! ???! ????? (CSSA):

It depends on the multimeter. I'd stick with the fast blow fuse and stop putting it in 'voltage' mode when you've got it connected to measure current.

Check to make sure that the fuse isn't being used as the current shunt

-- if it is, then you don't just need the right current rating, you need a matched fuse.

It's a glass one, 500mA fast blow according to the manual.

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Chuckle. If a fuse were used as a current shunt, then when the fuse blows, instead of a few millivolts across the fuse, the meter now gets the full voltage of whatever is being measured. The fuse holder contact resistance will probably be larger than the wire resistance in the fuse (fast blow). I don't think anyone uses a fuse as a current shunt.

That's the number of the plug, not the fuse:

It does have a fuse inside, but I don't know the value or type.

That's 'current' mode when you've got it connected to measure voltage, yes?

--Winston

Uhhh...

D'oh!

yes

Hush, you wasn't suppose to notice that! Built in obsolescence.

Jamie

Too hard to calibrate. :)

I used some test fixtures on the PRC-77 QA line for module interchangability that had to be returned to the cal lab if a module blew a fuse. !@#$%^&*( RCA/NATO design. @#$%^&*

Hope this helps answer your question!

John :-#)#

-- (Please post followups or tech enquiries to the newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)

Man-wai Chang Inscribed thus:

No !

"Jeff Liebermann"

A 13A, BS 1362 fuse is very much a Slow Blow !

.... Phil