On Jun 1, 12:09*am, "Phil Allison" wrote:
"Winston"



Phil Allison wrote:

I didn't know that.

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

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

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

** 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-Fus.../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?


Nice post a couple levels up.

Meters like the Flukes are "Category" rated - 1, 2, 3. When working on
high capacity services, like 1000A 480V, you really want a cat 1
meter. You won't wind up wearing it as in your previous post. The
problem is not just the meter. Arc in meter causes vaporized meter
leads that turns into an arc between busbars - very dangerous.

In addition to the nominal voltage you have the hazard of transients
that could start an arc which will then sustain at the nominal
voltage. In the US, OSHA may also take strong exception to using a
meter without the right cat rating.

One of the hazards in high capacity services is available fault
current, which can be 200,000A. Fuses have a rating for available
fault current. The fix is to use "current limiting" fuses. For high
currents they have a clearing time of under 1/4 cycle. You handle a
200,000A available location by the fuse clearing before the current
increases to anything near that value. The earlier Fluke fuse is
certainly current limiting. The fuse opens before the meter leads turn
to plasma.

The fuse in the later link is a mere 250V - not likely a cat 1 meter.
But a glass 250V GMA fuse in a meter may exceed the fault current
rating for the fuse. One of the fuses in my Fluke is 0.44A and is
almost certainly current limiting.

--
bud--