Hi Just a quick video about uh, multimeter fuses because uh, somebody on the Eev blog forum raised this and it's not the first time. and it is a legitimate Uh question. Why? on meters like the Bm-235 and a Bmr 786 here? 60 or 6000 count meter Or a 60 000 count meter? It's got a 600 milliamp range and it says it's fused. but the supplied fuse in it is not actually a 600 milliamps.

It's actually 400 milliamps. And I actually, um, sell spare fuses. uh for these meters and they're 400 milliamps. These are our Astm brand diffusers and I buy these in both.

They're very popular. I also sell uh, the bigger one for the 10 amp range. These are very nice. Uh.

fuses? The Astm ones anyway? Um, yeah, these are only Uh 400 milliamp fuses and that's actually what's supplied and that's actually what. Uh, Brymen recommend for these meters And this is not specific to Brian and it's for other Uh manufacturers as well. And you know there it is. Hv 620, 400 Milliamps, thousand Volts Ac Dc Ul listed of course by the way.

and by the way, uh, a thousand volts Ac Dc. Make sure if you're replacing the fuses on your multimeter, make sure you get the high thousand volt rated or at least you know like 600 volt uh rated ones because if you get like the like, the real cheap ass uh no name meters, they will have like only 250 volt mains rated fuses in them. and yeah, you don't want that, they can arc over and uh, ruin your day. So yeah, make sure you get like proper high voltage rating fuses if you're going to replace them anyway.

why do they have 400 milliamps in here if it's actually 600 milliamp range? So what happens if you actually put 600 milliamps through this meter? As you can see, I got 400 milliamps going through there at the moment and I've got one of these fuses hooked up and it's not blowing Because the rating of a fuse a 400 milliamp rating is not the rating that it actually trips at. That's actually the sustaining current rating. So in theory, we can leave 400 milliamps through this indefinitely and it will not break. It's only when it goes over 400 milliamps will it start to break.

And here's where it gets a bit loosey-goosey So let's take a look at the data sheet for the Astm fuse that we've got here, right? So we've got uh, the 400 milliamp job here, right? 1000 volt rated and a 400 milliamps is actually going to have quite a large voltage drop And I've done, you know, burden voltage videos about that. So yeah, putting a large amount of current through these, you can really get large burden voltage drops anyway. They don't actually give you an actual trip current on here, but that is its rated current is its implied hold in current. Now there is a mysterious uh figure here called typical pre-arcing and this is also known as uh, the melting thermal energy and it's given in uh, amp square or I squared T.

So it's a time unit. This is the thermal energy required in order to basically melt the fuse. and well, you can whack. You know, your 400 milliamps into that, but it's not really going to give you like the time taken to actually melt.

That's not really what it's uh for. So for practical purposes, it's more academic. For practical purposes, you really have to go to the characteristic curves. So you get these time versus current curves.

Any good. a fused manufacturer will give you these and you've got to look at the individual specific curve for the actual Uh fuse you've got. now. unfortunately, they don't have a curve for the specific 400 milliamp one.

But of course you know. Here's the 500. Here's the 315. let's just split it down the middle.

Well, let's look at 400 400. If we take 400 up, 400, up, 400, up, 400 up 400 Up Up At 400, it's going to be like it's practically off the scale. It's practically indefinite. I mean, it might blow eventually, especially if it, uh, is in a confined space and it's heating up.

uh, for example. So let's actually measure the temperature of this one because it is actually going to get fairly warm. So I've actually had this run in for I don't know, 10 15 minutes now or something like that. 37 degrees.

I'll set my air cons off so there's no airflow. But of course, if you put uh, one of these inside like a sealed fuse compartment inside a multimeter, then it's going to heat up more because it takes uh, you know, more effort for the heat to actually radiate out. But then again, the heat can actually go into it. Might also be lower because the heat can actually dissipate Our bloody thing.

The heat can actually battery. The heat can actually dissipate, of course, through the metal fuse contacts and into the Pcb traces and stuff like that. so they inherently have a bit of heat sinking on them. But anyway, you know this might eventually blow.

But you know, like, according to the data sheet, it's going to take a long time. and it's going to be like manufacturing tolerances in the Uh fuse as well the fuse wire itself, and well, you know, these are just like typical curves. They're not like absolute guaranteed anyway. Or what do we expect to happen at 600 milliamps? So if we extrapolate this up here, it's going to be somewhere between here and here.

And I put that I my mark. One eyeball says it's around about there. so we're looking at 100 seconds, 200 seconds, 300 seconds. Somewhere between 300 and 400 seconds.

It should probably blow at 600 milliamps, so you can. Like, according to the data sheet, it actually does have a significant amount of time. Uh, to actually measure, that's more than enough time to measure your uh, the current, your 600 your maximum 600 milliamps. But it's enough to protect the meter that it will eventually blow.

Or certainly if it goes to an amp, it's going to blow a lot quicker. What do we get for an amp? Let's have a look. So if take it up to an amp yeah it could blow. It's going to blow in a couple of seconds there and that's what you want.

And if you're going to get like an over current fault, you know might get a couple of amps or something like that and you can see how it gets. You know pretty non-linear here at the higher end because it's all a bit. Yeah it's more to do with the thermals and how quickly they blow on it's it's really complicated stuff if you want to get into the physics of you know the real physics of how uh fuses blow but bit non-linear but like you know it's going to be blowing in like the up at a couple of amps going to be blowing in like tens of milliseconds or something like that. Okay so I'm going to increase this to 600 milliamps.

We'll see how long with the stopwatch it takes to blow. There you go 600 milliamps as you can see more than enough time to take your measurement and it's not blowing yet. Of course it's had already had time to heat up from you know, tens of minutes 47 degrees. You know it's getting significantly hotter.

So oh no, sh. She blew. It was somewhere in 50 seconds there. Okay, so let's do that again.

600 milliamps and I'll get some data on a couple of these. So what we had are like 50 odd seconds before. Which is, you know, as I said, it's gonna vary quite substantially. If it blew in a couple of seconds, I would be uh, concerned.

But it's not. It's there. you go. I've got some heat sink in here, uh, from the leads, but it might have more if it's like on a Pcb.

And there's big current tray. you know, big clamps right around it. Thermal transfers Not very good. They're like little spikes on them, so you might actually get them better results inside the meter.

But as you can see, look, we're going for a minute 20 now. Oh, there we go. Minute 57. let's do another one.

There is really going to be like a large tolerance difference between these. I think if we test the whole box. Ah, now, of course it's got to be said that, uh, this is this specific type of fuse. another brand 400 milliamp.

Even if it's a thousand volts, all the specs seem the same. They might have, uh, substantially different characteristic curves than these Astm brand ones. So wait, there we go. Three minutes 47 was it? This one's up to 53 and a half after a minute 46.

this one is about to crack 60. Yep, at 2 minutes 40.. Well, this one's a champ. 63.

Of course we don't know what the internal temperature is because it's all embedded inside that the, uh, ceramic or the sound. Well, there we go. Three minutes 22 At 63 degrees, we have our first four minute joby. look at this little ripper.

Really big tolerance range on these fuses, which is, uh, why, you know you don't necessarily want to over range, uh, like overrate them. It looks like they've chosen it right? Ah, go, you little beauty there. It lasted three times longer than that first one we tested. That's incredible.

And this is what you have to account for when you're designing fuses like this into a system. Especially if it's you know, critical. You don't don't want to oversize and don't undersize them for your task. it's you know, And be aware of our surge currents as well.

Uh, by the way, I'm not turning this on 600 milliamps straight. I'm turning on 400 milliamps first and then ramping up to 600 so that you know any like power supply, um, turn on spikes. Don't the output capacitor or whatever doesn't dump some extra uh, charge into it and make it. you know, surge blow or something like that.

So because these are quick blow fuses, these aren't slow blow jobs. 77 degrees after seven and a half minutes? Wow, this is crazy. This is going to last four times more than the first one we tested from exactly the same batch. Like the same box.

Check it out. 83 degrees. So I actually, um, spoke to Brymen quite a few years ago. Now about, um, because somebody asked this exact same question.

so I thought I'd get Breiman's opinion on it. And they said, um, yeah, like exactly This is that. You know it holds up, uh, for long enough, but you don't want to oversize it, but then you can get potential temperature issues and that can damage other stuff in your meter or whatever. so you don't.

You know you don't necessarily want these things to, um, heat up too badly, but you want to protect them. It's a trade. but you want to protect your meter of course, so you don't make it too high, so it's a trade-off This is a super fuse. Oh yeah, yeah.

Bernie, Ernie, Bernie, Ernie Bernie don't touch these things, but that's that's a crit yet. 90 degrees? Wow. Oh there we go. It blew.

I missed it. walked away for a little bit, got our shortest one at uh, 45 second. Okay, what I'm doing is measuring the voltage drop across there and as you can see, it is sort of ramping up, isn't it? Oh, you wonder if there's I don't think I've ever experimented with this. I wonder if there's like a really rapid ramp up right near the point of failure.

You can really see what happens when these things really. Um, you know, heat it up because, well, it's changing the resistance of the filament and it's just going uppity, up and up so there. Yeah, that's probably like at 80 degrees or something. Now more.

Oh, and blow your bastard. By the way, I had what previous I went that I didn't shoot? Um, 45 seconds? Oh, we're gonna crack three volts. It's a massive drop. You really have to take all this into account when you're using your meter.

Burn voltage can be a real bugger, and, uh, changing your fuse from one brand to another can make a very large impact. And at high values like this, at, uh, really high temperatures? Yeah, I mean, it will go to that maximum of, uh, you know you'd be able to measure your 600 milliamps, but uh, at the huge cost of burden voltage? Wow, will this one crack the other one? I think we might have a new winner here. There's a huge difference in, uh, it's not like I'm adding. you know, really, any extra major heat sink in there by adding those two extra clips on? This is why when you're measuring these sort of currents, you want to use your amps range instead of your milliamp range.

You know, sure, you lose a digit, lose a digital resolution, but well worth it. I want to get this video done and edit the thing I came back to the lab. It's now. Uh, it's now 20 past nine Pm.

Wish the meter had a feature when it beep when it drops to zero. That'd be neat. Yes, a hundred. A hundred.

A hundred and 203 degrees. Oh, we just lost a digit of resolution on our floor there. Wow. this is actually this is turning into a bit of a valuable lesson.

Video here is that these things can get insanely hot. And you know, hot enough to damage your product in some way. Perhaps damage surrounding components or affect its performance or whatever. We've gone from like the shortest one 45 seconds to 12 minutes.

Like I could be here all night. Who knows what the upper bound on this is. All it takes is for the wire to come out. However, they stretch the filament wires in the machine that extrudes them or whatever.

However, it does it. I don't know how they actually manufacture that. That would be a fascinating video wouldn't it? Tour of a fuse factory? Um, yeah, it can't exactly travel at the moment, so it's not going to have any fuse factories here in Australia 111. It just ain't stopping so you can imagine if you had that like inside a sealed case.

I mean, I don't have my aircon here. Isn't there really no airflow in here? But still. we do have like it's just sitting there flapping around in the breeze, right? We'll just flap around in no breeze. It's a bit different to being cooked up in a uh, little fuse compartment.

sealed fuse compartment. Glad I was almost going to stop my testing at Five after the 45 second one I went. Oh yeah, did another couple and we're glad I did. Look at this.

14 minutes. I mean, what was the upper bound of that? A thousand seconds 1000 divided by 60? Um, you know that's 16.6 minutes. So you know that's like and that's just like eyeballing it and guesstimating that the characteristic curve is going to be in there somewhere. But you can see when you've got huge vertical lines like this and not much differentiation.

it's you know, the the more that these lines get vertical, the more they get vertical, the more uncertainty you have. That's how it works. If it's more sloppy like that, then you're going to get a more a narrow and narrower band of uncertainty for any given fuse. But they don't even give you uncertainty characteristics.

This is just like typical curves so like they don't even give you any notes for it. They just say here's the graph. You know we've measured it. I don't know, do they take averages? They don't say like so they don't really guarantee these things.

So I maybe say you know some other manufacturers might be different. You'd have to look at different, uh, data sheets and stuff. You've got to remember this graph. You know this axis.

The Y axis is log axes. Um, well, so is the uh X-axis as well. But come on, you got to give this video a thumbs up just for my perseverance here. Perseverance Rover just landed.

Fantastic. Did a video. I did a live stream of that. Come on, you've got to give this video a thumbs up just for me standing here wait for a bloody fuse to blow.

Ah, the glamorous life of Engineering. Video Blogging 118. Why is the current dropping? I've got a constant current power supply and unfortunately I can't show you what power supply I'm using because it hasn't been released yet. It's up there, hasn't been released yet.

There it is. 22 minutes. I actually know why the current drop though, because it we've reached the compliance voltage of the power supply. I had it set to 6 volts.

6.17 is the highest. So yeah, Unfortunately, I chose a six volt output power supply to do this test. Um, I. It didn't even occur to me that we can't that sort of compliance voltage.

That's just. that's nuts. Um, I might actually stop it because really, the only I did not put paper on top of that. It'll burn.

I've done that. That's not the first time I've actually, uh, burnt paper from my components. Uh, I've even put them in the report. I've even put the burnt piece of paper in the report to show the test report.

Anyway, long story. The only guaranteed spec they give you is up here in the uh, vague electrical characteristics and they just say, well, at one of its nominal current I nominal, um, it's it's gonna like. You know, it'll last at least four hours minimum. So in theory that 400 milliamp fuse can blow after four hours, but then they only specify like 120 seconds, absolute maximum 2.5 times the nominal current, and we're like nowhere near 2.5 times the nominal um current.

So yeah, I'm gonna take these curves with a grain of salt. I'm going to stop it and we'll um, I'll change my Uh supply and we'll try and wrap this thing up to say, 700 milliamps. see if it blows. All right.

So I'm back to 400 milliamps. We've got a compliance voltage of uh, 10 volts this time. So yeah, we're still at 3.6 volts. Anyway, let's uh, now, ramp this up to let's go 0.7 shall we? Let's try 700 milliamps.

So let's I'll reset that time. So that lasted, you know, at least 30 minutes. Here we go 0.7 Go. And whoa, Oh geez, no, we're Oh yeah, yeah, it, it blew, it blew straight away.

it just couldn't handle it. So yeah, so you can see that like any gross overload will blow these things, you know, or practically instantly. So it'll save your meter or save your circuit in a gross overload. And that's what fuses are designed to do.

They're designed for gross overloads. They're not designed for like, really, you know, discriminatory, Uh, current. Like, you can't really design a product for a fuse to blow within a specific region because look at the slope of these curves. You're just not going to get that.

When you have a slope like that. You might get other brands of fuses where you might get a more controlled characteristic. Uh, so to speak right? You know, a softer? I don't know what what would be the word for that. For you know, making the slope go.

You know, near vertical and having a big tolerance? You know, maybe a tighter tolerance for example? Um, something like that? You got a better word for that. Leave it in the comments. I'm sure it's a tip of my tongue if I actually thought about it. Anyway, yeah, you could.

you know different types. but then if the user goes and changes the fused, whatever like that can totally change your uh, product and change the safety of your product. It can, uh, change the characteristics, Um, based on burden, voltage, and other stuff. So yeah, you really have to take this stuff into account.

Anyway, that's fascinating. So I've got one. You know, 30 plus minutes. So there you go.

We went from 45 seconds at the lowest one. the first one was around about. that wasn't it. And then we went up to 30 plus minutes.

Massive tolerance in fuses like this. All right. What I've got here is the data sheet for a Seba brand. this is basically uh, the identical fuse to the Astm.

So uh, once again, fast blow fuse. 400 milliamps, a thousand volts. Uh, there's the actual uh part number there. Once again, you will, uh, list it.

So uh. The interesting thing is is that the characteristic curves are very different. A it only has one curve like there, so that actually has two for different current ranges. one for a hundred milliamps to 800 milliamps and one for one amp to two amps.

Now check this out for a hundred milliamps to 800 milliamps. They don't even give you a graph that extends down and this is uh, times the nominal current times. I n so they don't actually, so you have to multiply. So this is um, so this will be 400 milliamps.

They don't give you any separate characteristic curves for all the different currents. it's the one curve for all of them. So once again, like, it's totally different to the Astm fuse. Uh, which seems more comprehensive in terms of the characteristic occurs.

but interestingly look, it's the unfilled triangle. There it. the curve stops at four times the nominal current. So four fours, that's 1.6 amps beyond that, we just don't know.

I mean, you could you know kind of like say oh, it's going to be a similar curve to that, but they don't actually give you the data. so we have no idea. because we ours would be at 600 milliamps, it would be 1.5 times 400 milliamps. So it'd be this.

this is our seconds, but we just don't know the value. So anyway, I'm just going to whack this in and test it and see what we get. Okay, this is the Seba at 400 Milliamps. There you go.

Um, a little bit lower drop, but you know it's neither here nor there. It's heating up a little bit so let's choose 0.6 There we go. It's jumped up to 1.1 and let's see how long it takes. Okay, we're at four minutes now, only 1.2 volts drop and we're looking at 65 degrees there.

So it just goes to show that. Uh, really in. Well, in this particular case, um, if you were designing a product, these are Seba fuses. They're less predictable than.

I mean, you don't even have the data, You don't even have the data. You don't know what this code like. You can assume the Ker is going to do something. but at least the Astm fuses had all the multiple characteristics.

At least you could you know get a Um indication. You don't get that with the Seba fuses. So really, the Astm effusers are like more tightly spec. They're a better control.

They're better to design into your product than the Seba fuses in this particular case, because we have no idea. this could like just last forever. and well, if that's what you want and that's fine. But you know, if you're trying to protect your product or do whatever, the lack of data like this could be a real problem, you would have to like do your own testing and then continue to do testing to ensure that they haven't changed their manufacturing process, etc.

over time. Because you can't, uh, design this Seba fuse into your product and then measure them and they're all fine. You know you've done all your due diligence and everything's hunky-dory and then year or two later out in the field, you know all your fuses start blowing or they don't start blowing or whatever and you go back to them say hey, what's changed, what are you doing and they'll go oh sorry, we don't provide any data below. um, four times the nominal current.

So if you did your own testing, well, that's on you. That ain't our problem. Okay, we're getting towards 20 minutes now. 1.2 volts, uh, drop and 65 degrees there.

Uh, like yeah, this, this sucker is just not gonna blow. so I'll ramp it up to 700 milliamps. Okay, 700 milliamps go? Yeah, significantly higher. But yeah, it's going to take longer.

Much longer to blow than the uh Astm did this. Could this could last minutes at 700 milliamps. So this is a 400 milliamp fuse. No wonder they were a bit Mccoy with their curves over here because well, yeah, they just.

Well, they don't want to tell you no, I just don't think it's got the balls to do it. Not at 1.6 volts. I don't think the temperature is going to be high enough, but you know they've all got this secret. Saw their metallurgical, uh, secret sauce and everything.

But I? yeah, no. Should I take it 800? Yeah, why not? Okay, Eight amps, go. Two volts. drop.

This is double. It's rated Current: 400 milliamp fuse. Yeah, it's It's still only creeping up though. I I think it's going to last a significant amount of time.

double the current. It's A and after a minute, we're probably going to crack 100 degrees shortly. Okay, no, this is getting ridiculous. Five minutes at twice the current, and if you attempt to extrapolate the curve here, you're probably going to come a gutzer because look, this is.

uh, one second here. at basically, uh, two, two times the nominal current, which is what we're at. It should last that one second. But dude.

Nope. So obviously you know something. It's it's really ramping up when it gets past here. it's just going nuts.

That's why they don't bother. and look how they actually reset this. I mean, what do you choose if you're designing your product? Let's say, at four times nominal current? in this particular case, uh, 1.6 amps for a 400 milliamp fuse? Which? which data point do you choose? Do you choose this one or this one? But this is like Schrodinger's data. So yeah, it's ridiculous.

But anyway, you are down in like the you know, the millisecond uh, you know, tens of milliseconds region. So I guess it doesn't matter too much. Okay, so we have the data. Let's say three times here.

Three times normal current 1.2 amps. You expect that to blow in like, well, a couple of hundred milliseconds here. This is one second. So uh, let's go.

let's give that a ball. All right, Here we go. I'm going to take it to 1.2 amps for a 400 milliamp fuse. Let's give it a go.

I've currently I've just had it for like a minute. I've sort of like blown up. Let it cool down for a little bit at 400 milliamps. So I'm going to ramp it up right to 1.2 Here we go.

Oh an amp. Oh what? Oh, that's right. Sorry. Oh no.

it blew it, blew up. Sorry, don't my power supply. Again, power supply was only capable of maximum of an amp. So anyway, when you take it up to an amp, yeah, it blew within what? The sub 10 seconds there or something like that.

So okay. But yeah, in any case, I think there's a good reason why they're not giving you the data below like four times. Nominal bastards. And there are various standards for these fuses.

By the way, there's an Iec Uh standard which is Uh 6127-2 I believe is the latest one and also the Ul 248 standard which it looks like these fuses might actually go by. And of course it's hard to get these standards. but I was able to get this page which is a six by Uh 32 quick acting, low braking capacity. It's not a high breaking high voltage capacity one, I don't know if that changes.

please leave it in the comments if you've actually got uh, the standards and stuff. but anyway, it does give you like a maximum voltage drops, maximum power dissipation 1.6 watts and stuff like that for like a you know, nominal 400 milliamps so you know and take this with a grain of salt. but it does actually give you down here. Look, it actually doesn't give you anything actually below uh, two times nominal current.

It just says look at two times nominal current a maximum for a hundred milliamps to a 10 amp fuse is uh 20 seconds. So yeah, what happens at 1.5 like But then it does have like uh as part of the endurance testing down here it says oh 1.15 times nominal uh current for an hour and things like that it must do must survive 100 cycles at 1.05 times the rated current and stuff like that. So yeah, you can actually heat these things up and cool them back down. And there are endurance standards for these, so yeah, but it that just like complicates the whole thing, but it certainly might explain why there's a difference between the Uh Seba one and the Uh Atsm one.

They might be working to different standards, and well, if you're serious about this sort of stuff, like you've got to take all this into consideration. I found uh, something on the Ul 248 standard anyway, and uh, there's all these different classes and things like that. and of course, um, there's ambient uh, like D rating at temperatures. so you know if your products being used from like 0 to 40 or something like that like that can like make a fairly big difference in uh, the rating capacity uh, and the effect on the blowing time, the effect on the carrying current, and stuff like that.

So yeah, it's all it's all up in the air. Hold on to your hat. I just found this from Little Fuse: the importance of fused low overload. Uh, performance.

A low overload is like a low grade fever. It doesn't cause immediate depth, but indicates that something is wrong. It can cause localized overheating, weaken the spring clips, or damage the plating on the fuse holders, and increase their contact resistance. It can melt the solder on the surface mount fuses can melt plastic housings, and make fuses impossible to remove.

Yeah, all a valid design points you've got to consider anyway. And they say currents between 110 and 135 percent of fuse ratings present a severe challenge to the designers. They can subject parts to high heat for extended periods of time, and because fused behavior at these currents can be difficult to predict, the fuse does not blow before damage occurs. There can be claims under warranty, etc.

etc. Fuses behave in predictable ways and subjected to substantial overloads or short circuits, but low overloads exist in a less predictable realm. For example, 110 of rating of a mini automotive fuse will open somewhere between 100 hours and never at 135 percent of rating, The fuse opening time is between 0.75 seconds and 10 minutes. Yeah, that's the kind of variability we've seen here.

Published curves are available from the fuse manufacturer, However, typically they apply to overloads in excess of a hundred and fifty percent. Hence, why the Seba fused. While Cebu, they're just saying anything over anything under four times. Bugger it.

And they show uh, average characteristics. As I said, it's you know they're not guaranteed they only show averages. In fact, low value overloads are not generally considered part of fused specifications at all. Yeah, good luck.

Another source of difficulty is that different technical standards for fuses describe different behaviors at low overloads. For example, with one exception is impossible. It's impossible to refuse to satisfy both the Ul, Csa and the Iec rating standards, so pick one. Um calls for refuse to operate continuously at 100 of its rating.

A few is made to the Ul 248 and Op standard and operated at its rated current. Will eventually open for this reason. Url fuses are customarily operated at no more than 75. They're rated current.

That's interesting. And look at all these different Uh standards here. So there's various standards and at Uh, the 600 milliamps we're looking at here, or 150 of the rating? Well, these are the Sae and the Ul standards not even uh specified at all. This standard not specified like 60 minutes minimum.

for example. It's like it's all over the shop. Ah, but they say, look, there is a new R6127, Iec Uh-4 standard. Fuses must not open in less than one hour at 125 percent of the rated current, and must open within two minutes at 200 percent of the rate of current.

So I can still add twice the current. It can still last two minutes under this new Um Iec standard Nuts. And here's a table for different uh, little fews. uh, their different Uh types and what the applicable standards are.

and the opening time at 135 for example. And look, it's just it's all over the shop. Like 0.75 seconds to 30 minutes. Come on.

So basically one of the top manufacturers little fuse here. They're using like all the fluke meters and everything and they're just saying, throwing up their hands and just saying. you know it's complicated, it's like you're pretty much on your own and you know, leave it in the comments if you want me to do more detailed tests. but I'll leave it for now.

Um, because I've got no shortage of these. I've got many, many boxes. I sell these on the Evblog store. I bulk buy them like a thousand at a time, so it's not a problem.

If I want to do a huge number of tests, I'd have to automate this rig. There's no way I'd want to sit there. Maybe that's a it. Would that be a mini project anyone would want to see would be designing like a a little board that had like you know, like 20 fuse holders on it or something and 10 you measure 10 at a time.

You'd have like independent current generators for each one and then you'd have like a timer for each one and then you'd have like you could automate them. You would actually do that if you were a test engineer as I was donkey's years uh did test engineering and they they're the sort of jigs that you would actually uh design for stuff like this for measuring production. uh characteristic. Although you know, if you want the full characteristics and stuff like that, that's more complicated.

If you just wanted to like sample test fuses coming off the production line, you might actually have a jig. And they probably do have a jig and they might you know, uh, just uh. sample test. You know, a handful from each batch or something like that just to see that they're within the rather large tolerance that they actually, um, have here.

It's interesting because they sell like 315 millions, 400 milliamps, 500 milliamps. They don't even give you a curve for the 400 milliamp job, right? And the tolerance between, like, even the 315 milliamp and the half amp here. Like, you might find that the half amp might, uh, blow quicker than a particular 315 milliamp, just based on the tolerance and the massive slope of this line here. So yeah, Fuses? fascinating business.

Anyway, I think this video is probably fascinating enough to elevate to the main channel, so if you liked that video, please give it a big thumbs up. As always, comment down below: Do you work in a fuse factory? I'm sure somebody out there does. There's always a viewer out there that has worked in something or other that I mentioned doesn't matter how obscure it is, and uh, leave it in the comments down below, so I hope you found that fascinating. Yeah, Fuses.

anyway. So to answer the question, like is a 400 milliamp fuse suitable for a meter like this, and Brime is not the only one that sort of like underrates their fuses like this. and there's probably good reasons why you would actually want to do that. And yeah, sure, you can measure up to your 600 milliamps, but it could, uh, blow.

depending on what type of fuse you've got, it'll eventually blow. Could blow in seconds. Tens of seconds, Minutes. Tens of Minutes.

So huge variability. Anyway, fascinating stuff. Catch you next time you.