Electronics > Repair

Fluke 179 Multimeter Fuse

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bostonman:
That's what I assumed, but the list of meter model numbers isn't in the quantity five part number description implying they are different fuses.

Obviously I understood they are the same fuse, but they are confusing the viewer by not listing the 179 in both part numbers.

Gyro:
On a whim, I revisited this the other day - this being, the early Fluke approach of fitting series 600mA 20mm x 5mm ceramic fuses (250V, sand filled, 1.5kA breaking) in series with a standard Fluke large 3A 600V 10kA meter fuse on the mA current ranges. In my case on a Fluke 25.

The cost advantage of only having to replace a cheap sacrificial 20mm fuse most of the time is clear but the discussion was centering around whether this early approach was safe, whether the 20mm fuse could explode or arc over under extreme fault currents, and whether it was actually safer to replace the 20mm fuse with a piece of copper rod or whatever (probably yes).

I've now fitted a Littlefuse 230V 10kA GDT from stock, in heatshrink for extra protection, across the rear of the 20mA fuseholder. My thinking is along the lines of the GDT capturing the current if the 20mm fuse blows at mains voltage high fault current, and taking out the main 10kA fuse.

This is a very academic question, as I am not in the habit of using DMM current ranges, blowing fuses, or using DMMs on high energy circuits. I have Cat III+ stuff for that anyway. I'm certainly not going to waste the cost of the 10kA breaking fuse with some sort of high energy capacitor discharge test rig. I just wondered what others think.

The only potential fault scenario I can think of at the moment is the 20mm fuse failing to break the fault current and its arc voltage being too low to trigger the GDT.

bastl_r:
The folllowing  video  shwos what hapen when a 100000µF 700VDC capbank will be discharged on a low price Multimeter. The last one is complete without a fuse. :bullshit:


And this is what hapen when the discharge blow a Fluke fuse

Gyro:
A good demonstration of arc flash - although the meters seem to fly apart too quickly to sustain a flame arc! A big shrapnel field though. Probably penetrating wounds rather than burns.

That test setup looks pretty dodgy for that amount of store energy though.  :scared:

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