DMM woes

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Tactical Oatmeal
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DMM woes

So I have a Craftsman DMM item no. 82141 as seen HERE.

It is giving me a consistent issue of blowing through the 10A fuses when I use it to take tailcap readings and I have no idea why…

I am not leaving the leads on the subject for longer than 10 seconds at a time nor am I running more than 3A through the meter so what gives? I really hope that this is not an issue of me being a dum-dum…

MRTdiver
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Is it very old?   Can you return it?  I suppose you would have already done that, but I thought I would ask first.

You set the meter to 10A DC and move the pos. lead to 10A terminal?

quote from HKJ:  "Select DC current measurement and move the plugs to the 10A/20A input terminal. For flashlight measurement it is best to select the highest current range, i.e. 10A or 20A range, this is done to keep the voltage drop in the meter as low as possible. For a multilevel flashlight on the lowest levels it can be necessary to use a more sensitive range, but this is only recommended if the reading can be keep below 1/10 of max. on the selected range. For lights that uses multiple amperes a clamp meter is better (see below)." (from here)

נֵר־לְרַגְלִ֥י דְבָרֶ֑ךָ וְ֝אֹ֗ור לִנְתִיבָתִֽי   (Psa 119:105)   

Tactical Oatmeal
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I have had this one for about 3 weeks now…. I returned the last one bacuase it was defective

ChiggerPepi
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I have the IDENTICAL DMM and mine works great! It’s also quite accurate.

agenthex
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Tactical Oatmeal wrote:
So I have a Craftsman DMM item no. 82141 as seen HERE.

It is giving me a consistent issue of blowing through the 10A fuses when I use it to take tailcap readings and I have no idea why…

I am not leaving the leads on the subject for longer than 10 seconds at a time nor am I running more than 3A through the meter so what gives? I really hope that this is not an issue of me being a dum-dum…


I don’t see how it’s even possible to blow a 10A fuse unless you’re shorting the battery.

Reading this makes you smarter: http://lesswrong.com/

HKJ
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Tactical Oatmeal wrote:
So I have a Craftsman DMM item no. 82141 as seen "HERE":http://www.sears.com/craftsman-multimeter-digital-with-8-functions-and-2.... It is giving me a consistent issue of blowing through the 10A fuses when I use it to take tailcap readings and I have no idea why... I am not leaving the leads on the subject for longer than 10 seconds at a time nor am I running more than 3A through the meter so what gives? I really hope that this is not an issue of me being a dum-dum...

 

You cannot blow a 10A fuse with 3A, maybe it is the low A fuse you are blowing?

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

Tactical Oatmeal
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No. I am for sure blowing the 10A fuse (And yes the fuses are in the correct locations). When testing, I take the positive lead from the 200mA socket and plug it into the 10A socket, COM does not change.

While testing, I use the COM lead to hold against the negative side of the battery and the 10A lead touches the flashlight body to complete the circuit…

Will reversing this have any ill-effects?

MRTdiver
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Tactical Oatmeal wrote:
While testing, I use the COM lead to hold against the negative side of the battery and the 10A lead touches the flashlight body to complete the circuit... Will reversing this have any ill-effects?

No, you can do it reverse.  You're just making a complete path, like you said.

Sounds like you're doing the right things. If you have any questions about your fuse I have a 10A 250VAC one I can send you.

Otherwise I suggest you take it back again.  bummer

נֵר־לְרַגְלִ֥י דְבָרֶ֑ךָ וְ֝אֹ֗ור לִנְתִיבָתִֽי   (Psa 119:105)   

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Tactical Oatmeal wrote:
No. I am for sure blowing the 10A fuse (And yes the fuses are in the correct locations). When testing, I take the positive lead from the 200mA socket and plug it into the 10A socket, COM does not change.

While testing, I use the COM lead to hold against the negative side of the battery and the 10A lead touches the flashlight body to complete the circuit…

Will reversing this have any ill-effects?


Reversing the leads will only show as a negative current on your DMM meter , so no ill-effects.

It certainly looks as though you have the meter leads in the right sockets and a 3A current should not blow a 10A fuse.

When you have the tailcap on the torch , can you switch the torch on and off OK ?

With the tailcap removed , when you apply a short-circuit from the torch body to the battery negative , does the torch switch on OK ?

If you use one of your spare 10A fuses as a short-circuit between the torch body and the battery negative , does the torch switch on OK without the fuse blowing ? … If the fuse blows , then either the current is greater than 10A or the fuse is rated lower than 10A.

I hope you resolve the problem soon.
.

march.brown

Tactical Oatmeal
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Well craftsman requires the use of fast-burn fuses…. is this really a necessity? the fuses that I took out are indeed 250V 10A fast burn fuses. Can I just use non-fast burn fuses?

The lights in question that I had used this DMM on indeed function properly (i.e. I can bypass the tailcap with a short and switch modes, tailcaps function properly etc)

However I have not tested the fuse in line with the short, so when I get some fuses I will try that out.

garrybunk
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You could do like a friend of mine would do back when we were teenagers - wrap the blown fuse in aluminum foil.  However, I would not suggest this! 

-Garry

(This was a joke, do not do this!)

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old4570
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Strange …

Some thing is up if the 10A fuse is blowing at 3A , so the MM reading is 3A when the fuse blows 1/ Dont have a second MM to check Amps [ Flashlight ]

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

Major
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This sounds very strange indeed, the only thing i could think of is that the fuse is rated at 1.0A and the printing looks like 10A, as i’ve had bulbs and fuses that are very hard to read. Also is the fuse actually blown? Maybe the action of changing the fuse can disturb a bad solder joint in the meter which makes connection for a while until the current flowing breaks the dodgy connection and makes things appear like the fuse has blown.

Tactical Oatmeal
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here are some pictures of the fuse in question

The link on these fast burn fuses are so skinny…

and as you can see it is a 10A fuse

Major
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ok i’ll shut up this is way over my head! Strange indeed.

Tactical Oatmeal
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So, is it acceptable to run non fast-burn fuses in this DMM?

Are the fast-burn fuses the root of my issue?

Major
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I think the fuses are for CAT rating safety incase one does something stupid or accidental. Two of my old DMM’s dont have a fuse at all on the 10A range. I’ve measured 15A in the past! The leads get warm but the meter handles the power no problem! I would try the slow blow fuse and see if it makes any difference. What i’m trying to say is, replacing the fuse might alter the safety rating slightly if you work with mains electricity, but for flashlight measuring nothing bad will happen at all.

Tactical Oatmeal
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Major wrote:
I think the fuses are for CAT rating safety incase one does something stupid or accidental. Two of my old DMM’s dont have a fuse at all on the 10A range. I’ve measured 15A in the past! The leads get warm but the meter handles the power no problem! I would try the slow blow fuse and see if it makes any difference. What i’m trying to say is, replacing the fuse might alter the safety rating slightly if you work with mains electricity, but for flashlight measuring nothing bad will happen at all.

Thank you for this information! To be honest, the only time I use the 10A setting os for flashlight related testing….

Maybe I will use Garry’s idea and wrap it in foil!

MRTdiver
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That's the same fuse in my Ideal DMM.   per my manual: 10A (250V) fast blow fuse.

נֵר־לְרַגְלִ֥י דְבָרֶ֑ךָ וְ֝אֹ֗ור לִנְתִיבָתִֽי   (Psa 119:105)   

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Something else is going on here.. Fast or slow, 3A doesn’t blow a 10A fuse..

You must have a light that spikes to over 10A… That’s really the only possibility. 10A fuses simply do not blow with 3A of current.. They just don’t..

I am currently extremely busy with work. Please do not expect a response from me quickly. I will be dropping in as time permits, but the amount of time I can dedicate to responding to topics and PMs is very limited.

Tactical Oatmeal
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any issues with that MRTdriver

MRTdiver
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Tactical Oatmeal wrote:
any issues with that MRTdiver

I don't recommend my Ideal DMM.  I was just saying it looks like we use the same fuse.  When we were doing some electrical work I was getting some funny readings. 

I'm currently looking for a DMM that will give reliable tail cap readings w/out spending retail $$ for a Fluke.

נֵר־לְרַגְלִ֥י דְבָרֶ֑ךָ וְ֝אֹ֗ור לִנְתִיבָתִֽי   (Psa 119:105)   

Tactical Oatmeal
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PilotPTK wrote:
Something else is going on here.. Fast or slow, 3A doesn’t blow a 10A fuse..

You must have a light that spikes to over 10A… That’s really the only possibility. 10A fuses simply do not blow with 3A of current.. They just don’t..

Makes sense. But even with this, could the batteries used during tail cap readings provide over 10A? I used some Protected Angelfire “3200mAh” (yeah right) and some salvaged Sanyo UR18650A cells from a laptop battery.

What could cause the light to spike to such a high current?

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Sure, for a short spike, it's easy to do 10A. Add to that factor your fuse is also fast burning. Maybe the two comes together and causes this.

But what light were you measuring? Single/double/triple battery in series etc? 

PilotPTK
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Tactical Oatmeal wrote:

Makes sense. But even with this, could the batteries used during tail cap readings provide over 10A? I used some Protected Angelfire “3200mAh” (yeah right) and some salvaged Sanyo UR18650A cells from a laptop battery.

For very brief duration, absolutely. I would bet they can provide 50 or 100A for somewhere between a few microseconds and a few milliseconds – maybe more..

Tactical Oatmeal wrote:

What could cause the light to spike to such a high current?

[/quote]
1) Crappy driver design
2) an intermittent short that only happens when something ‘moves’ to just the right place
3) A short that you’re somehow causing

I am currently extremely busy with work. Please do not expect a response from me quickly. I will be dropping in as time permits, but the amount of time I can dedicate to responding to topics and PMs is very limited.

Tactical Oatmeal
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The only lights that I have measured are P60 hosts.

PilotPTK;
1) Crappy driver design;
One of my dropins “was” a three mode XML that I had issues with…
as you can see HERE
Now that it seems to be brighter than ever before, I wonder if this is the culprit… (although the highest reading I got out of it was 1.9A with the craftsman leads)

ChiggerPepi
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If you change to a slow blow fuse, or a higher rated fuse, the worst that I would assume could happen is you might fry the DMM. Certainly do NOT remove (and short) the fuse completely though!

My first suspicion is something to do with the driver.

Tactical Oatmeal
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I won’t bypass the fuse (I was kidding earlier).

I will however, try a slow-blow fuse once I can get my hands on some.

PilotPTK wrote:
For very brief duration, absolutely. I would bet they can provide 50 or 100A for somewhere between a few microseconds and a few milliseconds – maybe more..

Maybe because of this, a fast-blowing fuse would be too quick to blow as it would be more sensitive to very brief spikes above 10A. I would think that a slow-blow fuse might not blow on these same occurances. (Correct me if I am wrong)

E1320
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I don’t mean to fuel any flames but my Fluke 179 blew the 10 amp fuse a while ago and all I ever test with it is drop ins under 5 amps. It is almost ten years old and Fluke charged me $12 bucks for a new fuse which sucked but I assumed the fuse wore out after a while since I definitely didn’t spike it recently.

I am already visualizing the duct tape over your mouth.

PilotPTK
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Fuses shouldn’t really ‘wear out’. Cars have fuses – would people tolerate their engine controller fuse ‘wearing out’ while they’re on the freeway?

Something spiked it. I promise.

I am currently extremely busy with work. Please do not expect a response from me quickly. I will be dropping in as time permits, but the amount of time I can dedicate to responding to topics and PMs is very limited.

ChiggerPepi
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PilotPTK wrote:
Fuses shouldn’t really ‘wear out’. Cars have fuses – would people tolerate their engine controller fuse ‘wearing out’ while they’re on the freeway?

Something spiked it. I promise.

+1

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