I'm trying to learn and test current with my cheap china multimeter. Unfortunately, there is a glass fuse .5 amps and another one I think 10 amps. I connected something wrong and is not forgiving so now a trip to the hardware store in the morning.
Is there a different piece of hardware I can replace for the .5 amp glass fuse that can be reset, so I can just press a button or reset the thing?
Stick with the proper fuse, have several on hand.
The more fuses you burn out the less you will burn out 
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DocStein99:
I'm trying to learn and test current with my cheap china multimeter. Unfortunately, there is a glass fuse .5 amps and another one I think 10 amps. I connected something wrong and is not forgiving so now a trip to the hardware store in the morning.Is there a different piece of hardware I can replace for the .5 amp glass fuse that can be reset, so I can just press a button or reset the thing?
Hi,
You'd have to design a really fast circuit to turn off the current because fuses used in meters have to be fast acting and most circuit breakers dont act fast enough to ensure protection of the meter.
You could check into resettable fuses though, which reset automatically. They may be fast enough.
I found a resettable fuse on mouser:
It trips at .6 amps, 125v maximum. I have never used them before, didn't know if they did anything else tricky that would interfear with the measurement of current.
Remember, the speed at which the fuse reacts, is important.
Those polyfuses are slooooow.
The circuit and the meter will fry before a polyfuse will trip.
Polyfuses are for slow overloads. There is one in the USB power circuit of your Uno.
Stick to the 0.5Amp fastblow glass fuse.
Leo..
DocStein99:
I found a resettable fuse on mouser:0ZRM0030FF1E Bel Fuse | Mouser Europe
It trips at .6 amps, 125v maximum. I have never used them before, didn't know if they did anything else tricky that would interfear with the measurement of current.
Hi,
Yeah it looks like these will not be fast enough. Sometimes we even have to hope the regular fast blow fuses will be fast enough so it looks like it is best to stick with the original design or else be prepared to design something better.
Circuits that have to be really fast usually depend not on opening the circuit but by diverging the current around the sensitive part, such as a crowbar circuit. It would take some work unless you can find one on the web that would work with a meter. Once the current is branched off to another circuit, that circuit could contain a slower fusing mechanism which protects the source current from staying too high for too long.
Ok. I thought there could be a quick easy answer, but I'll just replace the fuse and keep a pack of them taped to the back of the meter. I got too much other stuff to research. Thanks.
I was not getting a reading in 10a range either. Don't know how that fuse could have blown out since i'm just using usb power and maybe a 12v lithium battery pack. Or I thought the range was too small to measure in 10a mode. I wasn't getting anything, it took me about an hour to figure out the fuses were blown.
I can just put fuses in the dumb thing. I just prefer not to get stuck in 2 more months again when I want to measure milliamps, and forget how to hook it up the exact right way before breaking another fuse that's buried somewhere in the warehouse of components I have to search through.
I can't remember what I did. I know I was trying to figure out why i wasnt getting a reading, and remember which of the 3 or 4 different combinations I needed the leads plugged in, to take a current reading. Eventually the youtube video explained, I blew the fuse inside - where I found the blown fuse.
I could not get a reading on the 10a fuse, and just assumed the miliamps were too small for 10a mode. I dont know if that fuse is blown, it looks made out of cardboard, something I cant see through. Got mad and put the meter back together, and came up with idea - it should just have resettable fuses, or a circuit breaker, or something I didn't need to wait for a store to open tomorrow to wait in traffic and buy something for $1.00.
DocStein99:
Don't know how that fuse could have blown out since i'm just using usb power and maybe a 12v lithium battery pack.
This also makes me very suspicious that you are using the meter in a wrong way. Have a very close look at arduino_x's question. Because it is not a problem at all to blow such a fuse with 5 or 12V.
Yes the meter still works for everything else. I'm sorry, I just feel frustrated....
I don't see a fuse or anything on that. I saw alot of old-school analog panel ma meters, and I didn't see any fuses on those either. I want a tool that's more forgiving to my clumsy mistakes.
This ampmeter measures the voltagedrop over a shunt resistor.
There is no fuse because its damn cheap and your shunt is acting as a fuse. This is at max a 1 W rated resistor with 0.05 ohms. ==> 4.7 Amps and you are at the maximum rated thermal stress. Go higher, go bang the resistor.
if you want something that is really "forgiving" but a bit dependent on the environment (magnetic fields), and not that accurate go use a Hall sensor like this. It can measure up to 5 A, but you can pass over 30 A through without destroying it (for a short time). If you want it to be indestructable under every common situation (except trying to fry it with a electric welder) you can use this. You poke a maximum diameter wire through the hole and thats where your current to measure flows. This should withstand direkt poking into the mains, pc psu, ... because the limiting factor is only the big fat cable and you will drip your house fuses before it gets destroyed.
Just shield it good and zero it before use and you are good to go. (If you want a finished solution you don't have to build, go grap something like this). Have fun.
Ok. I thought there could be a quick easy answer, but I'll just replace the fuse and keep a pack of them taped to the back of the meter. I got too much other stuff to research.
That's right.
I researched this issue for a customer who needed 250 multimeters for a school program. They had "too many blown fuses" by the students. We tried to find a meter that would not blow the low-current fuse if connected across Arduino 5V. We settled on THIS One. which had enough internal resistance on the low-current scale to 'protect' itself. Of course that means it affected some circuits and led to some situations of inaccuracy. In the school environment that was "OK"..
I use my low-cost "Decent Chinese Multimeters" like THESE and occasionally blow a fuse.. Works fine for me..
DISCLAIMER: Mentioned stuff from my own shop...
In my school I was lucky enough to have an electronics class, with an exceptionally great teacher. I returned back to the school to thank him, and talk about how my life has changed - just because of his education. He explained back to me, the electronics classes were shut down, because they needed more of the budget to pay for the maintenance on the football field. Same thing with photography classes, wood shop, silk-screen printing, offset printing. The only thing left for the students at that school to learn is the useless garbage that nobody uses unless they help their own children with homework.
Changing the blown fuse in a meter is DISTRACTING task. I feel sorry for the teacher of that class, probably an entire year went by they just spent their time replacing fuses for the students instead of teaching skills. Why, in 2016 - they still make multi-meters that do not solve this problem is not known to me. It took car makers about 50+ years to finally make intermittent delay windshield wipers.
This reminds me of the old joke "the transistor will blow to save the expensive fuse" which was typical years ago with lots of stuff where the transistors were running close to their limits. 
So. A trip to the radio shack, after 30 minutes in traffic due to road construction detour. They did actually have a .5 amp 125v fast fuse. $3.50 for 4 tiny fuses.
Radio Shack does not stock 10a, 250v fast acting fuses (the other fuse needed for the meter). It's another hour tracking down a pack of fuses from mouser and pay $9 to ship. Or I buy a pack of 100 from china from ebay for $.82 that will take 6 weeks to deliver and hopefully send the right ones.
DocStein99:
Changing the blown fuse in a meter is DISTRACTING task. I feel sorry for the teacher of that class, probably an entire year went by they just spent their time replacing fuses for the students instead of teaching skills. Why, in 2016 - they still make multi-meters that do not solve this problem is not known to me.
There are still many things in life which need to be done manually - maybe for our own good.
For a multimeter, a fuse that sacrifices itself can help save people's lives (at the expense of the innocent fuses own life that is), and save the lives of some devices. So, for safety, it might be better to have a multimeter shut down permanently (especially for measurements of relatively high current) - until the fuse is replaced. For beginner students, the electronics is generally at a very low risk level. But, as somebody rightfully mentioned before, it's a very good thing to teach students to think about what they're doing before doing it, particularly in electronics classes. Sure, not every beginner student will pay careful attention, even if you tell them. But reminding them about it will be for their own good in the long run.
The problem is solveable. Many problems have multiple solutions. One is to know roughly what level of current is expected to be measured, and to know in advance what setting (eg. current measuring setting, not voltage measurement setting) the meter needs to be set at.
There are also relatively inexpensive Hall effect current sensor devices that are fairly robust against relatively high current (that could be used).
Radio Shack does not stock 10a, 250v fast acting fuses (the other fuse needed for the meter). It's another hour tracking down a pack of fuses from mouser and pay $9 to ship. Or I buy a pack of 100 from china from ebay for $.82 that will take 6 weeks to deliver and hopefully send the right ones.
This becomes a problem no longer once you've got the goods (and enough of them). You're certainly not going to blow 10 Amp fuses on a regular basis.
gpsmikey:
This reminds me of the old joke "the transistor will blow to save the expensive fuse" which was typical years ago with lots of stuff where the transistors were running close to their limits.
Well, actually if we consider a proper DMM fuse the joke can be sadly true in a lot of cases...
Ciao, Ale
DocStein99:
I was not getting a reading in 10a range either. Don't know how that fuse could have blown out since i'm just using usb power and maybe a 12v lithium battery pack.
Your "12v lithium battery pack" can easily generate a short-circuit current of hundreds of amps in a short burst, so that makes perfectly sence.
I just want to know - HOW are you measuring current? How is the meter connected - in series with the load or across? The latter is very incorrect and will not work. A typical newbie-fault.
// Per.