Products > Test Equipment
Multimeter fuses
Mikke:
--- Quote from: Berni on July 13, 2016, 05:23:52 am ---If you work with only low power things then there is no real danger of using a cheap meter with the cheap fuse it comes with. And if you work with large industrial switch panels designed to carry 1000s of amps in normal operations you obviously shouldn't even come close with anything other than a proper high quality meter with proper fuses.
--- End quote ---
You don't have to work with switch panels or power sockets to get big short circuit currents. A normal car battery has a very low internal resistance and short circuiting one can result in more than 1000 amps. Luckily the test leads have also some resistance. So in case of measuring battery voltage with meter set to "amps", the actual current through your multimeter will be somewhat less.
Being careful helps, but mistakes do happen and then you need the proper fuse.
joeqsmith:
--- Quote from: Mikke on January 29, 2017, 08:25:07 am ---
--- Quote from: Berni on July 13, 2016, 05:23:52 am ---If you work with only low power things then there is no real danger of using a cheap meter with the cheap fuse it comes with. And if you work with large industrial switch panels designed to carry 1000s of amps in normal operations you obviously shouldn't even come close with anything other than a proper high quality meter with proper fuses.
--- End quote ---
You don't have to work with switch panels or power sockets to get big short circuit currents. A normal car battery has a very low internal resistance and short circuiting one can result in more than 1000 amps. Luckily the test leads have also some resistance. So in case of measuring battery voltage with meter set to "amps", the actual current through your multimeter will be somewhat less.
Being careful helps, but mistakes do happen and then you need the proper fuse.
--- End quote ---
Most automotive will be 24V or less. Do you feel a 250V glass fuse will rupture with a direct connection to the batteries?
joeqsmith:
My first few cars used glass fuses. A quick search on eBay...
http://www.ebay.com/itm/Vintage-9-Boxes-Fuses-Bowes-Littlefuse-Buss-Automobile-Garage-Gas-Station-Sign-/190878236552
I have some 9A 32V automotive fuses from Bowes and Little Fuse. They are a 1/4 X 7/8. You can see them next to the fuses from the UT61E and a 1000V Little Fuse. I would guess these would rupture before a 250V glass part.
vk6zgo:
--- Quote from: Berni on July 13, 2016, 12:50:22 pm ---Yes the fuse is there only for the time when you stupidly forget you are plugged in to amps and try to measure the voltage of a supply. Just when the said supply is a 12V wall wart all you get is a bit of a spark and the wallwart getting warm. When you do this on a giant 3 phase bus bar the result is a huge arc flash and the chard remains of the electrician that did the stupid mistake.
Voltage overloads in multimeters are usually not as concerning since you rarely encounter more than 1000V at home and if you do it tends to be low current. So as long as you don't try to measure the output of a microwave oven transformer you should be safe.
The question is if a DIYer does the same amps jack mistake in his home mains distribution panel. Could a cheep meter and fuse become more dangerous in such a situation versus a HRC fuse?
I personally never have taken care of using only good quality meters on regular household 230/400V mains. I picked up whatever meter was handy, be it my good Agilent or the cheap 20€ rebadger.
--- End quote ---
Such accidents which do happen are newsworthy,& are tragedies to those concerned & their families, but are really statistically insignificant.
I have (& I am sure many others have) measured phase -to- phase on a (then) 254/440v system,using AVO 8,early Beckman DMMs,Fluke 77,& a few other multimeters.
When people set out to do such measurements,they approach them differently to "quick checks"on lower voltage circuits.
You don't just "grab the nearest meter", prance up to the 3 phase board like a Smurf and poke the probes in higgledy-piggledy.
The correct approach is to make sure that the test leads are NOT in the current sockets,or if the connections are switched,the meter isn't on a current range.
With the leads correctly configured for voltage readings,check that the meter is switched to the appropriate AC voltage range.
Check the condition of the leads.
Be like Santa & "check it twice".
To be really sure,with the multimeter set up correctly,connect it across a known source of AC voltage ( normally in Oz,the nearest single phase 230v GPO).
This shows your meter actually works---a dead meter would be more dangerous than anything else.
Now,if you can possibly do so,rest the meter on the floor,or some other support,not handheld.
If at all possible,connect the probes before applying power to the circuit to be tested.
In many cases,you don't need to test "Phase to Phase" & can just measure the lower voltage "Phase to Neutral",or cheat even more & go "Phase to Earth".
MacMeter:
--- Quote from: nanofrog on January 29, 2017, 01:49:45 am ---
--- Quote from: MacMeter on January 29, 2017, 12:42:20 am ---FROM THE ONLINE EEVBlob BM235 USER MANUAL:
Fuse F1 for uAmA current input: 0.4A/1000V DC/AC, IR 30kA FAST fuse or better; Dimension: 6 x 32 mm
SIBA 70-172-40 FF400mA
Fuse F2 for A current input: 11A/1000V DC/AC, IR 20kA F fuse or better; Dimension: 10 x 38mm?Bussman DMM-B-11A?Littelfuse FLU011
--- End quote ---
The uA/mA fuse (F1) isn't all that expensive (Galco carries the Siba 70-172-40 for $7.43).
They also carry the Littlefuse FLU011 for $32.10 (best price I've seen, but still on the expensive side IMHO).
The SIBA equivalent P/N = 5019906.11, and it's a LOT cheaper @ $8.13 from TME (they're located in Poland, but they do ship to the US). :-+
--- End quote ---
Forget GALCO, unless you want to buy (10) fuses. I just called them, not in stock, won't be stocked, a 10 fuse order limit. This for the 400m/A fuse. So the search for a reputable USA site where I can buy 3 of these fuses continues!
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