Fuse: fast blown vs slow blown

[Man-wai Chang]

How dangerous is it to replace a 500mA fast-brown fuse with a 500mA
slow-brown one?

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[Phil Allison]

"Man-wai Chang"

How dangerous is it to replace a 500mA fast-brown fuse with a 500mA
slow-brown one?

** Confucius once say:

" The quick brown fox jumps over the lazy dog "

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



..... Phil

 

[Phil Allison]

"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.


** Globemaker is one of those personages who sincerely believes that " Star
Trek " is a documentary.

And he has pointy ears too.

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



.... Phil

 

[Man-wai Chang]

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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[Man-wai Chang]

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.

Is the 13A BS1362 fuse a fast blow one?

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[Man-wai Chang]

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.

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

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[Winston]

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.

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

--Winston

 

[Jamie]

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

yes

 

[Jamie]

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.

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

Jamie

 

[Baron]

Man-wai Chang Inscribed thus:

Is the 13A BS1362 fuse a fast blow one?

No !

 

[Phil Allison]

"Jeff Liebermann"

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

** Funny, I have any number of fuses in my bins with "BS 1362" printed on
them.

<http://en.wikipedia.org/wiki/BS_1363>

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

**From the very same Wiki:

http://en.wikipedia.org/wiki/BS_1363#Fuses

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




..... Phil

 

[Winston]

On 05/31/2011 10:16 AM, Winston wrote:
(...)


Uhhh...



D'oh!

The fuse for my Fluke 79 multimeter retails for $10.00.
(Ten U.S. Dollars)

http://www.flukeonlinestore.com/3478682.html

Guess what prompted that discovery.

Go ahead. Guess.

--Winston <-- It's better, now.

 

[Phil Allison]

"Winston"

The fuse for my Fluke 79 multimeter retails for $10.00.
(Ten U.S. Dollars)

http://www.flukeonlinestore.com/3478682.html

Guess what prompted that discovery.

Go ahead. Guess.

** That fuse is designed to protect the multi-meter, its leads ( and you )
from a worst case scenario.

That scenario is when you probe a 415 volt, 3 phase power outlet with the
meter accidentally set to the 10 amp range.

A standard glass fuse would simply arc from end to end, the probes and leads
would explode and cover you in hot metal and the meter would become a write
off.

The specified ( fast acting, high rupture current, high voltage fuse ) would
merely produce a loud pop.


..... Phil

 

[Winston]

"Winston"



** That fuse is designed to protect the multi-meter, its leads ( and you )
from a worst case scenario.

That scenario is when you probe a 415 volt, 3 phase power outlet with the
meter accidentally set to the 10 amp range.

A standard glass fuse would simply arc from end to end, the probes and leads
would explode and cover you in hot metal and the meter would become a write
off.

The specified ( fast acting, high rupture current, high voltage fuse ) would
merely produce a loud pop.

I didn't know that.

How about this one?
http://www.flukeonlinestore.com/3478747.html

--Winston

 

[Phil Allison]

"Winston"

I didn't know that.

** Cos you know **** all about anything.

How about this one?
http://www.flukeonlinestore.com/3478747.html

** Standard glass (fast) fuse by the look of it.



..... Phil

 

[Winston]

"Winston"
(...)


** Cos you know **** all about anything.

It's a continuing problem.
Watta ya gonna do.

** Standard glass (fast) fuse by the look of it.

It must be ~36 times safer than a commodity GMA
fuse in a multimeter application, yes?
http://www.amazon.com/125mA-250v-Fuses-0-125A-5x20mm/dp/B004HLZYVI

Fluke wouldn't overcharge for that part either,
surely.

--Winston

 

[Phil Allison]

"Winston"

It's a continuing problem.
Watta ya gonna do.


It must be ~36 times safer than a commodity GMA
fuse in a multimeter application, yes?
http://www.amazon.com/125mA-250v-Fuses-0-125A-5x20mm/dp/B004HLZYVI

Fluke wouldn't overcharge for that part either,
surely.

** The price is very steep.

But I expect the fuse IS safe when used in the Fluke DMMs it is specified
for.

The scenario with a 0.125A fuse is nothing like the one with the 10A range
fuse.

Typical 0.125A rated fast fuses have resistances of 8 to 10 ohms - which
limits the fault current to a value the fuse can easily break.

A 10 amp fuse may well have a resistance of only a few milliohms, so the
fault current is only limited by the resistance of the DMM's leads.

A current of 40 amps is easy enough for a small fuse to break, while one of
over 4000 amps is not.

Capice?


..... Phil

 

[Winston]

"Winston"
(...)


** The price is very steep.

We agree.

But I expect the fuse IS safe when used in the Fluke DMMs it is specified
for.

Both the 'Fluke' brand and the commodity brand are safe, I suspect.

It wouldn't shock me to learn both kinds are sourced from the same
place.

The scenario with a 0.125A fuse is nothing like the one with the 10A range
fuse.

Typical 0.125A rated fast fuses have resistances of 8 to 10 ohms - which
limits the fault current to a value the fuse can easily break.

A 10 amp fuse may well have a resistance of only a few milliohms, so the
fault current is only limited by the resistance of the DMM's leads.

A current of 40 amps is easy enough for a small fuse to break, while one of
over 4000 amps is not.

We agree on that, too.

--Winston

 

[Phil Allison]

"Winston"

We agree.

** Yawnnnnnnnnnnnn....

Both the 'Fluke' brand and the commodity brand are safe, I suspect.

It wouldn't shock me to learn both kinds are sourced from the same
place.

** Nothing shocks a fuckwit like you.

We agree on that, too.

** GIANT Yawwnnnnnnnnnnnnnnnnnnn

Piss off wanker.


.... Phil

 

[Man-wai Chang]

** Funny, I have any number of fuses in my bins with "BS 1362" printed on

them.

Coz you are in USA, not Hong Kong (ex-UK colony)!

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