Multimeters with Easy to Change Fuses (Like Metrix MX 24B)

[tzonehunter]

I teach high school physics and electronics. My experience is that no amount of instruction prevents students from accidentally blowing fuses when they're first learning how to measure voltage and current in a circuit.

I would love to buy a classroom set of these:
http://www.industrial-needs.com/technical-data/images/multimeter-metrix-mx24b-fuse-box.jpg

but can't seem to find them anywhere. Does anyone know of something similar or where I can get these? Thanks!

 

[Vanadium 50]

I have a Fluke 77. Changing a fuse is about twice as hard as changing a battery. The biggest issue is that the fit is very snug. It helps to be able to push from the other end.

 

[Student100]

Extech makes meters that're probably sufficient for your needs as well, and cheaper than Flukes - although I like my Fluke more.

For the Extech model I have, it's remove the the protective cover, 4 screws, pop out the old fuse and put in new fuse. 5 Minute job.

If your students are blowing fuses regularly enough that you need some kind of quick fuse release system you're doing something wrong. Try to explain good tool use practices, and have them replace fuses themselves during the lab.

 

[f95toli]

May I ask what they are actually doing when they are blowing a fuse?
I have been using multimeters on a daily basis for well over 15 years and I've never had a fuse blow. Back when I was a TA I also spent 2-3 years supervising labs in courses in basic electronics; as far as I remember .I never had to replace a single fuse (although I did had to stop a few students from nearly killing themselves).
That said, these were all university students (mainly future science teachers) so maybe the type of experiments they were doing was different from what you would do in high school.

 

[Vanadium 50]

As an alternative, could you use cheap multimeters? They cost less than a fuse on a good one.

 

[tzonehunter]

For the Extech model I have, it's remove the the protective cover, 4 screws, pop out the old fuse and put in new fuse. 5 Minute job.

If your students are blowing fuses regularly enough that you need some kind of quick fuse release system you're doing something wrong. Try to explain good tool use practices, and have them replace fuses themselves during the lab.

Some ask how it is that high school students hook up multimeters incorrectly and have even overtly stated that "I'm doing something wrong." The latter comment is odd and comes across as arrogant.

In regards to the former, we explicitly teach, through a variety of techniques, how to hook up and use multimeters and breadboards. That being said, these are kids, and they make mistakes. Many have never turned a screw driver, swung a hammer, etc. We don't have the time to teach such things in our Physics classes, thus I do not feel comfortable making students change the fuses on traditional multimeters themselves. Simple things such as turning the dial on the multimeter to measure potential and pausing at the amp setting, learning what a parallel circuit actually looks like in a real circuit vs. a diagram, learning how the connections in a breadboard work, etc. result in fuses being blown. It's part of the learning process.

Some ask why the 5 minutes of time is a big deal. We have 40 minute class periods. If this happens to say, 2 or 3 out of 10 or 12 lab groups, then that's 10 - 15 minutes of time wasted that could be spent on instruction during the lab.

 

[Student100]

Some ask how it is that high school students hook up multimeters incorrectly and have even overtly stated that "I'm doing something wrong." The latter comment is odd and comes across as arrogant.

In regards to the former, we explicitly teach, through a variety of techniques, how to hook up and use multimeters and breadboards. That being said, these are kids, and they make mistakes. Many have never turned a screw driver, swung a hammer, etc. We don't have the time to teach such things in our Physics classes, thus I do not feel comfortable making students change the fuses on traditional multimeters themselves. Simple things such as turning the dial on the multimeter to measure potential and pausing at the amp setting, learning what a parallel circuit actually looks like in a real circuit vs. a diagram, learning how the connections in a breadboard work, etc. result in fuses being blown. It's part of the learning process.

Some ask why the 5 minutes of time is a big deal. We have 40 minute class periods. If this happens to say, 2 or 3 out of 10 or 12 lab groups, then that's 10 - 15 minutes of time wasted that could be spent on instruction during the lab.

It's neither odd nor is it arrogant..

Simply let them change the fuses themselves, using lab time. That should slow the rate of blown fuses as students now have an incentive not to do dumb things with their tools- i.e. spending all their time changing fuses.

Okay, so you don't trust them with screwdrivers, but somehow trust them around voltage sources? Kids have to learn these things eventually. If it were my class the first lab section would be about proper tool use. Screwdrivers, soldering irons, meters, etc., anything that they might need to use in the lab section. Kids need to learn how to (properly) use tools eventually.

It's not my class, however, it's your class. Good luck in your quick fuse replacement hunt.

 

[f95toli]

Some ask how it is that high school students hook up multimeters incorrectly and have even overtly stated that "I'm doing something wrong." The latter comment is odd and comes across as arrogant.

That was not the intention. The point I was making is that most multimeters are fused at something like 400-500 mA (and probably about10 A for the high current input) which is quite a lot of current; way more than you would ever use in a typical lab circuit (or even a "real" circuit). Hence. the reason why none of my students -as far as I can remember- ever blew a fuse is simply that I don't think they ever did a lab where it would even have been possible to get 400 mA somewhere in the circuit by making a simple mistake; and the only piece of kit that could even generate that amount of current would have been the benchtop DC supply (which could probably give something like 1A at most if shorted). Hence, there was very little chance of any student blowing a fuse by making a simple mistake, they would have had to do something way outside the lab instructions to actually blow a fuse.
The reason why I never blow fuses is the same: none of my (many) sources can generate more than 120mA (the exception being the magnet power supplies that can give 60-120A, not something you'd use a multimeter on).

Hence, I was simply curious about what type of experiments you are doing if the students a frequently blowing fuses?