A viewer asked this, and it's probably an interesting question.
Why is the "defacto" standard multimeter current range usually 10A and not say, 20A?
They used a 16A breaker as a practical example of usability.
Yes, many will go 20A or something for X seconds, and fuses won't just blow at 10A or 11A or whatever.
And yep, there is internal shunt heating, contact ratings and all sorts of things that play into this.
But why are most meters seemingly designed around 10A and not 20A for example?
Would have made sense in the days of early 3 1/2 digit 1999 count meters.
I don't think I've ever really thought about it...
I would guess it has something to do with the dissipation of the current shunt. On a usual 2000 count it would be 200mV x 20 A = 4 W. Seems to be pretty much in the confined space inside a handheld instrument.
I would guess it has something to do with the dissipation of the current shunt. On a usual 2000 count it would be 200mV x 20 A = 4 W. Seems to be pretty much in the confined space inside a handheld instrument.
Sure, but you design around that by halving your shunt value. These are specially manufactured 4 terminal wire shunts.
So why 10A instead of 20A when almost all digital meters started out as 2000 count?
Sure, the spec will change if you do that, but 10A isn't the greatest spec anyway, so why not 5A and get even better spec? Or 2A and use your full 2000 resolution?
Probably more to do with the leads than the meter. 20A leads would be much chunkier.
Shunt linearity?
When current shunts get hot, their resistance changes. It can be compensated for but it is not a simple linear equation. So it makes sense to try and limit the heating of the shunt rather than try and compensate for the heating.
That is my guess.
Probably more to do with the leads than the meter. 20A leads would be much chunkier.
Why would you let that dictate your meter design decisions? Sell pricer 20A probes to those that need them.
Shunt linearity?
When current shunts get hot, their resistance changes. It can be compensated for but it is not a simple linear equation. So it makes sense to try and limit the heating of the shunt rather than try and compensate for the heating.
That is my guess.
Halve the shunt value, it heats up the same.
Wouldn't you just hang a clamp meter to monitor current of an entire breaker circuit? I also don't know what 20A affords me over 10A beyond that. I've got 3 different clamps for different currents personally. Are there any real safety restrictions? Eventually the shunt needs to be shielded if you're looking at a couple hundred volts and 20A. Self heating is gonna be worse and the typical solution of smaller value shunt could be more susceptible to noise since you need to amp the signal more. Considering there are 20A meters though my real guess is tradition.
Wouldn't you just hang a clamp meter to monitor current of an entire breaker circuit? I also don't know what 20A affords me over 10A beyond that.
So why not 5A instead?
The point I'm trying to make here is why was 10A settled upon as a kind of defacto standards here?
If it's because it's a nice round value, and then everyone copied it, then so be it, but that's the devil in the question...
Considering there are 20A meters though my real guess is tradition.
Likely, but
why....
Who started it? Who copied it first and why etc etc
The point I'm trying to make here is why was 10A settled upon as a kind of defacto standards here?
It's a nice round number.
Who started it? Who copied it first and why etc etc
Probably comes from older analog meters, which usually went up to 10.
Back in the good old days, analog multimeters usually didn’t have current ranges beyond a couple amperes. This changed when affordable digital multimeters emerged in the eighties of last century. For instance, we got 20A ranges in the most popular Metex 36XX and 46XX meters (which were subsequently sold for many years also under various other brand names), but they were unfused. The internal shunt was nothing more than a piece of copper wire, several millimeters in diameter.
This has all changed at the end of last century, when it became fashionable to have the high-Amp socket fused. So it probably has something to do with the fuse and maybe the new safety requirements could not be met for currents that high.
EDIT: Apart from that, I for one don't care, as I hold the view that high currents are a task for external shunts or clamps anyway.
Hmm good question. There are some 20A meters out there but most are 10A.
I think its just going for a nice round number since most meters are also 1000V these days even tho the 1000V mark doesn't really have any special significance. Why not just 500V? its still enough for mains. Or if meters are commonly 2000 count why not have them go to 2000V?
Tho i do agree that if you want to measure above 10A in mains then using a current clamp is a better idea anyway. Such currents would cause a good deal arcing on probes.
Tho i do agree that if you want to measure above 10A in mains then using a current clamp is a better idea anyway. Such currents would cause a good deal arcing on probes.
>10A is pretty common on low voltage DC supplies and products. Meters aren't just for AC.
Back in the good old days, analog multimeters usually didn’t have current ranges beyond a couple amperes. This changed when affordable digital multimeters emerged in the eighties of last century. For instance, we got 20A ranges in the most popular Metex 36XX and 46XX meters (which were subsequently sold for many years also under various other brand names), but they were unfused. The internal shunt was nothing more than a piece of copper wire, several millimeters in diameter.
This has all changed at the end of last century, when it became fashionable to have the high-Amp socket fused. So it probably has something to do with the fuse and maybe the new safety requirements could not be met for currents that high.
Yep, now we are getting somewhere were I think the real answer(s) lies.
Everyone copied the early Flukes for example, in specs in features, and many other ways. So I'm half expecting the answer to be "it's because Fluke used 10A first".
The Fluke 8020A and 8060A were only 2A, so they seemed to be following the "1999 full resolution" thing with those.
But then the first Fluke 77 had 10A instead of 20A... what was the limitation or reason there?
Probably comes from older analog meters, which usually went up to 10.
I don't recall a tradition with analog meters having 10A?
AVO, 12A top range:
https://en.wikipedia.org/wiki/AvometerNo explicit explanation may be possible to find when it goes back that far. Fluke stuck at 10A but the 8000 series which started DMMs as a product segment were only 2A requiring an (optional) external shunt for 10A continuous, 20A peak just as their current models. The 10A figure probably entered some large contract specification and has just sat there, a competitor hasn't convinced the customer for the important need to increase this specification so its obviously of niche use.
Tho i do agree that if you want to measure above 10A in mains then using a current clamp is a better idea anyway. Such currents would cause a good deal arcing on probes.
>10A is pretty common on low voltage DC supplies and products. Meters aren't just for AC.
That was mostly in response to the reasoning of 16A breakers being common (In the EU they are indeed everywhere).
But DMMs usually have way too much burden voltage to be used on a 5V 20A supply rail anyway. Maybe we need a high current model of the µCurrent ?
Probably comes from older analog meters, which usually went up to 10.
I don't recall a tradition with analog meters having 10A?
No, but they had 3 and 10 at full scale for voltage, so it makes sense to use the same for Amps.
Thinking about automotive stuff, breaking the circuit isn't usually useful. You don't want to need to take connectors apart and have all sorts of pigtails. You just throw a clamp on the right wire and read it on your meter. That's for any motor really, battery monitoring you can't break the circuit because you could be changing something by doing that, starters, battery charge rate. Even when I was at an electronics manufacturing company when doing repairs you don't always know what's there. Schematics and service manuals just aren't around. Wave soldering machines, lead cutters, washers, electric forklifts... Even 20A you don't want to risk a fuse for nothing and with the added effort of manually passing current through the meter. I know there are edge cases but it really seems to me to be a feature looking for a niche.
Probably comes from older analog meters, which usually went up to 10.
I don't recall a tradition with analog meters having 10A?
Not 10A, but the scales generally went to "10".
I'm just guessing though. There might be some really popular old meter that went to 10 and everybody simply copied it.
You could ask Brymen and UEI why both your meters are 10A and see what they come back with just out of curiosity Dave. There may be an answer none of us have thought of or it may just be tradition like you say. It will for sure be interesting to find out.
6000 counts is quite common, too. Why aren't 6000 count meters rated to 60A?
Back in the early days most of my weekend work involved automotive and marine fitouts so the higher 20 amp current range on my Metex M-3650CR was handy for testing things like headlights, spotlights, winches, relays and a stack of other stuff. Nowadays I use clamp meters for those high current applications but back then there wasn't much to choose from nor the availability that we have today.