Author Topic: Blown fuse with high but finite resistance  (Read 1643 times)

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Offline kenshi

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Blown fuse with high but finite resistance
« on: May 30, 2015, 09:59:19 am »
At work this week, a device blew an HRC fuse, although it wasn't completely blown. When I put the multimeter on it, it measured a few megaohms of resistance. To me, this seems like an incredible unlikely scenario. I would think this could only happen if there was an overload of current which caused the conductor to start vaporizing, but the current abruptly shut off just as there was an extremely tiny thread of conductor remaining. Is this a less rare phenomenon than I think? What's going on here?
 

Online Rerouter

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Re: Blown fuse with high but finite resistance
« Reply #1 on: May 30, 2015, 10:01:55 am »
your talking megaohms, the vaporised metal may have been deposited along the line of the arc, reducing the gaps between pieces of metal enough to form a leakage path,
 

Offline mikerj

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Re: Blown fuse with high but finite resistance
« Reply #2 on: May 30, 2015, 10:03:48 am »
It's probably just a film of metal deposited on the filler inside the fuse when it ruptured. 

To get a resistance of megaohms in a piece of wire an inch or so long would be almost impossible.
 

Offline kenshi

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Re: Blown fuse with high but finite resistance
« Reply #3 on: May 30, 2015, 10:23:42 am »
That makes sense. I hadn't thought about the fact that that metal vapor would condense somewhere.
 

Offline Kedar264

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Re: Blown fuse with high but finite resistance
« Reply #4 on: May 30, 2015, 11:43:33 am »
Its the resistance of your hands :-+
Its No Magic, dont touch at end of your dmm probes
 

Online Ian.M

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Re: Blown fuse with high but finite resistance
« Reply #5 on: May 30, 2015, 01:02:58 pm »
Its the resistance of your hands :-+
Its No Magic, dont touch at end of your dmm probes
s/Its the/It may be the/

Don't *ASS*U*ME* the O.P. is an idiot.  Ask!
 

Offline miguelvp

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Re: Blown fuse with high but finite resistance
« Reply #6 on: May 30, 2015, 04:32:14 pm »
s/Its the/It may be the/

HipChat much? (allthethings)
 

Online Ian.M

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Re: Blown fuse with high but finite resistance
« Reply #7 on: May 30, 2015, 04:43:08 pm »
No.  The use of SED substitute command syntax by hackers/programmers to highlight mistakes in a previous non-editable message goes back to long before the likes of snapchat.  I don't know when I picked it up, but it was probably on USENET, though it may have been on FidoNet in the late '80s.
 


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