Looking for a fuse time curve

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I'm looking at a DMM that uses a 10A/600V (5 x 20mm) fast blow fuse. That's all the info I've got. I'm having a hard time googling a time curve for it. Is it because this is insufficient information to identify this fuse?

I'm trying to understand for how long I can continuously monitor a 3 Amp DC current without blowing this fuse.

Thanks!
 
The time curve describes how quickly the fuse will blow at various currents above the fuse rating. Currents below the rating can be carried indefinitely.
 
Key point is stick with FB fuses, a SB fuse even with a lower rating will blow the internal fuse.

If the DMM is an expensive one, it may have a internal fuse too that's hard or expensive, like a
Buss "BBS-_" Midget cartridge 'meter' fuse costing $15 - $23 each!

Figure that SB fuses are 4 -5 times slower and pass higher current before letting go.
 
Originally Posted By: Quattro Pete
I'm looking at a DMM that uses a 10A/600V (5 x 20mm) fast blow fuse. That's all the info I've got. I'm having a hard time googling a time curve for it. Is it because this is insufficient information to identify this fuse?

I'm trying to understand for how long I can continuously monitor a 3 Amp DC current without blowing this fuse.

Thanks!


I don't know who makes it, and until my friend Google came through would have bet there were no 600V fuses that size ... but see http://cci-parts.com/product_info.php?manufacturers_id=&products_id=317.

As others have said, a 10A fuse will carry 10A "forever"
 
Originally Posted By: George Bynum
As others have said, a 10A fuse will carry 10A "forever"

So what's this warning in the DMM owners manual all about?

Quote:
Input Limits:
10A Current AC or DC: 30 seconds max. every 15 minutes)
 
Originally Posted By: Quattro Pete
Originally Posted By: George Bynum
As others have said, a 10A fuse will carry 10A "forever"

So what's this warning in the DMM owners manual all about?

Quote:
Input Limits:
10A Current AC or DC: 30 seconds max. every 15 minutes)



That's the limitation of the meter's circuitry. It's been my experience that cheap meters serve as protection for the fuse.

The Fluke 170 series, for example is also rated at 10A AC or DC. They can read an overload of 20A for 30 seconds. That's just one differences when you step up to a quality meter.

Ed
 
You should be able to with no problem. Power (heat) is proportional to current squared, so 3 amps would generate about 10% as much heat as 10 amps. The 30 seconds every 15 minutes sounds like a hear issue.
 
Originally Posted By: Quattro Pete
Originally Posted By: George Bynum
As others have said, a 10A fuse will carry 10A "forever"

So what's this warning in the DMM owners manual all about?

Quote:
Input Limits:
10A Current AC or DC: 30 seconds max. every 15 minutes)

Probably more because of the wire size of the leads.
 
"Input Limits:
10A Current AC or DC: 30 seconds max. every 15 minutes)"


The reason for this is a cheap meter will have a "shunt resistor" to get a voltage drop that
indicates the current. They get hot. so that's the reason for the time limits.

On expensive DMMs, they'll have a current shunt made from Manganin alloy (84% copper, 12% manganese, and 4% nickel)
that can handle a full current with no time limits. The alloy allows accurate measurements
even when the shunt gets warm.
 
Originally Posted By: George Bynum
hear here ... I'm not hot unlike the HEAT I should have used. Thanks for catching my mistake.

George

Thanks for clarifying.

I wasn't trying to nitpick. I figured it was a typo, but I truly couldn't figure out what it was supposed to be. Now it all makes sense. Thank you.
smile.gif
 
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