Blew a fuse, and then blew a fuse

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After many, many years I accidentally blew the fuse in my Fluke 117 multimeter.  No biggie I think, just open the case and find out what I need to order, or pick up locally.

 

There is a BUSS fuse part number DMM-11A in there I find.  Ok, run the part number and..........................

 

WTH!!!!

 

This fuse ranges in price of $5.00 if I go the Ebay route and order it from china:

https://www.ebay.com/i/163559600...

 

or $47.00 for 5 if I order them from Allied

https://www.alliedelec.com/produ...

 

Heres a little more reasonable:

https://www.amazon.com/DMM-11A-F...

 

 

Guess this will learn me to be a little more careful

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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That is why so many DMMs on the bench don't work for current.

 

West Coast Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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I hear ya, but I use the current setting on this all the time so I have to take my medicine.....

 

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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I feel your pain.  I blew a (milliamp scale) fuse in a Southwire (Klein) meter I got at Lowe's.  The price on a replacement blew my mind.  Something like $27.  )^;   I contacted Klein and the nice lady ended up sending me one gratis.

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Check on Aliexpress, that is where I bought mine :(

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You could probably rig a cheaper fuse of about the right current rating for much less money. However, the cheap replacement won't have the same high voltage rating and probably higher resistance. If other people often use your meter this could save money.

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Bought one off Amazon for $7.00 will be here Friday.

 

bobfrench wrote:
However, the cheap replacement won't have the same high voltage rating and probably higher resistance.

 

I am guessing that these are indeed semi custom designed for the DMM market just for the resistance....or they just created a bull**** part number to up the price

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Fast fuses are expensive! The yield is not good as they lose a lot in testing!

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The biggest deal is the high voltage. If you are measuring a current on a 440v circuit and the fuse blows it will be the open fuse between you and the high voltage.

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Been there, as have many members of the Forum, I'm sure.

 

There's those that have blown the fuse on their meter, and there's those that will...

 

I remember blowing the fuse on an O'scope once.

I didn't even know that they had fuses, and I thought I'd blown the entire slide - in amp / module.

 

Playing with defibrillators can be hazardous to one's instrument's health!

 

JC

 

Edit:Typo

Last Edited: Wed. Feb 27, 2019 - 08:45 PM
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Tried to measure the short circuit current of my solar panel, then I remembered my meter was only good for 2 amps!

Took me for ever to find a replacement fuse, I could find lots of 2a fuses, but none as short as the one in my Fluke meter.

Ebay finally came to the rescue, I promise to be more careful in the future!  No, really I will!  cheeky

 

Jim

 

Click Link: Get Free Stock: Retire early! PM for strategy

share.robinhood.com/jamesc3274
get $5 free gold/silver https://www.onegold.com/join/713...

 

 

 

 

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real fuse = $9.50  

 

1/4" length of wire-wrap wire [ notched or filed to be thin enough to open at the desired current ] = $0.00002

 

.... decisions, decisions....

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There's a few demonstrations on the interwebs where there is a comparison between a real fuse and a fool's fuse. If you only measure low voltages, then the fool's fuse is probably adequate. However, the average Fluke meter is rated for much higher voltages. If you happen to measure 3 phase bus bars or the like, then having the proper fuse is wise.

 

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Simonetta wrote:

real fuse = $9.50  

 

1/4" length of wire-wrap wire [ notched or filed to be thin enough to open at the desired current ] = $0.00002

 

.... decisions, decisions....

 

Kartman wrote:

There's a few demonstrations on the interwebs where there is a comparison between a real fuse and a fool's fuse. If you only measure low voltages, then the fool's fuse is probably adequate. However, the average Fluke meter is rated for much higher voltages. If you happen to measure 3 phase bus bars or the like, then having the proper fuse is wise.

 

 

Kartman wins. 

 

I use this meter for EVERYTHING from coin cells up to 480vac three phase.  The meter cost me over $200.00 new and it has been indispensable to me over the years, so if the proper fuse costs $10.00, it is what it is.  YEah, that little piece of wire wrap wire could do the trick, but if I accidentally make the same mistake I did and the wire wrap wire melts whos to say it wont melt onto something else inside the meter causing a much bigger problem.  Hopefully I wont pop the replacement fuse.

 

$7.00 for a fuse may be high, but I just got back from Home Depot as I needed a 5x20mm 1 amp glass fuse and the pack of 2 cost over $4.00! surprise

 

 

On a similar note, yet off topic.

I can remember back in the day in school there was a very opinionated woman in my class...sat in front of me and she had an argument for EVERYTHING.  we received back our recent test scores and she has a hissy fit that the instructor marked her answer that a good fuse has infinite resistance, where the rest of the class wrote that a good fuse has zero to a couple ohms resistance.  When the instructor asked her to elaborate how she came to this conclusion her reply was that because the fuse blew open, it did it's job, hence it is a good fuse.  A bad fuse would not have blown open.  the instructor then tried to diplomatically explain what was taught in class etc, but this person was having none of it, and instead became more and more angry to the point of yelling at the instructor.  In the end she went to the head of the school and threatened a lawsuit unless the instructor was fired, and the her test score was corrected for that question.  I don't know what happened to her, and I wasn't dissapointed that she never returned to class either.  THe instructor finished the semester and then left the school for a private sector job...

 

Thinking back on that day I do kinda wonder.......What is a good fuse?  Anybody want to chime in?

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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At least it didn't occur to you that a .22 rifle round would fit just fine...  laugh   S.

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An ideal fuse would have zero resistance and interrupt an infinite amount of volts and amps at precisely the rated current. Unfortunately real fuses are nothing like this. Seemingly very simple devices, but when you delve into them, there's a lot to know in order to correctly specify them, especially in higher energy applications.

 

 

I used to repair crt monitors and SMPS as a sideline. You could tell by just looking at the mains fuse how it blew. If the glass was intact and no vapourisation, then it probably failed due to thermal stress or minor overcurrent. If the glass was cracked and black inside, then you knew there was a short circuit involved. Invariably the SMPS mosfet was blown apart. If there was significant over-voltage, the MOVS would also be vapourised. When you have a major overcurrent event, the fuse element blows but you get an arc - which is effectively a short circuit. This vapourises the fuse element and plates copper onto the glass. Eventually the arc dissipates and the circuit is broken.

 

One thing to remember - "the fuse is to protect the wire, not the load"

 

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For those of you thinking "it's only a fuse - why the fuss ?" this Fluke Apppliation Note explains quite scarily why you should use the right safety level instrument according to what Category circuits you are working on.

 

https://content.fluke.com/promotions/promo-dmm/0518-dmm-campaign/dmm/fluke_dmm-chfr/files/safetyguidelines.pdf 

 

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bobfrench wrote:
The biggest deal is the high voltage. If you are measuring a current on a 440v circuit and the fuse blows it will be the open fuse between you and the high voltage.

 

That doesn't necessarily blow the fuse.

Do it right, and the tip of your probe vaporizes first as it shorts the HV . . .

 

cheeky

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This reminds me of a cute Fluke story.  I was troubleshooting a Thermatool resistance welding system with a plant electrician.  We were perched on top of the oscillator cabinet where the filament transformers and grid resistors were located.  This thing used a pair of water cooled triodes to produce 360 kw at 400 kHz, the hv power to the tubes being 22 kv at about 25 amps.  He wanted to measure the grid voltage with his Fluke and just stuck the probe right on there before I could even speak first word of this sentence: "No, don't!".  The oscillator was a grounded plate configuration so the grids were sitting about 22 kv above ground.  That nice little dvm was instantly transported to an as-yet unknown dimension, never to return.  The residue that was left in our dimension was almost unrecognizable.  Amazingly, the dinky little plastic probe handle kept this guy from getting killed.

 

Tom Pappano
Tulsa, Oklahoma

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Mine came at a *bit* lower voltage . . .

 

My father borrowed my meter, and was "showing me how" to check when he shorted it across 220v on my mother's dryer . . . I think I still have that inch-shorter probe with it's mushroom head *somewhere* . . .

 

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I've had a couple of "events" myself 8)  I was using my portable Hitachi scope to observe the output of a 40 hp, 480 volt variable speed drive.  All I needed to do to pick up plenty of signal was just lay my probe on the insulated center portion of one of the large motor fuses.  This was working fine until one of the techs asked a question.  When I turned toward him I inadvertantley let the probe slide along the fuse body until the little grounded ring near the probe tip touched the fuse terminal.  Wow, were we all surprised 8)  About a .25" inch hole was "cut" out of the fuse terminal and the ground ring of my probe was 50% gone.  No other damage to the probe, its lead, or the scope 8)  I still keep that big fuse on my bench to remind me to pay attention!!

 

Tom Pappano
Tulsa, Oklahoma

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This one sits on my shelf in front of me as a constant reminder of what happens when things go wrong...

 

#1 This forum helps those that help themselves

#2 All grounds are not created equal

#3 How have you proved that your chip is running at xxMHz?

#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Did I ever tell the story of the batch of 'faulty' thermal fuses??

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Speaking of "fuses" ..

 

I saw a student @the school car repairshop using a ?? - What's it called ?

 

To tigthen the positive wire on a 24v truck on battery frown

 

Then he discovered that the chassis was GND

2/3 of the "ring" disapeared in a giant spark.

 

No one was hurt , but ther had to be a lot of molten metal in the air.

 

/Bingo

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What's it called ?

Students Welding rod 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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The skinny little meter wires just aren't enough for 10 or 20 amp measurements. I used to use a 13 inch piece of AWG #10 wire with big ring terminals as a shunt resistor. It's 0.001 ohms per foot so the meter reading is 1 millivolt per amp with the meter leads connected 12 inches apart. It works to measure the starter motor current of a 466 cubic inch diesel school bus. I now have a store bought amp meter shunt rated at 50 amps. It's beefy enough for 600 amps for a few seconds.

If you ever work on a car watch out. If you disconnect the battery then reconnect through an amp meter it will likely blow a fuse. My van flashes all the lights at once when the battery gets connected. I think Ford doesn't want me to measure the battery current when everything is off.

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tpappano wrote:
Amazingly, the dinky little plastic probe handle kept this guy from getting killed.
Serious injury can result from the flash (IIRC, third degree burns at close range)

Very recently noticed the warning placard on an enclosure's front door stated for one to wear PPE including a face shield.

PPE - Personal Protective Equipment

There's a YouTube video on flash exposure with and without PPE.

 

P.S.

tpappano wrote:
"No, don't!"
That can result in an issue due to one being surprised.

Am glad y'all did the two-man rule though might consider being immediate to each other.

Case - a professor was observing a student, student moved their diagonal cutters towards the cable, professor gently and assertively placed a hand over the student's hand (the student had missed a step, power off [been there, done that, mini-mushroom cloud])

A pair of brains, a pair of hearts

 

"Dare to be naïve." - Buckminster Fuller

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I was jinxed! I just blew the fuse in my Fluke! Putting the probes across a battery whilst in amps mode wasn’t a good idea. My excuse was the sun was setting and I couldn’t quite see the colors. $10 bucks gone in 10 microseconds.

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Welcome to the club!

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user