Measruement range for Amps for portable Multimeters

[Hans Gebert]

Hey all,
most Multimeters out there have different inputs for uA-measurements and measuremet above (10A).
I just wondered if the 10A option is really needed. 70mA can kill within milliseconds..So when I know that there will be currents above serveral mA I usually use my Clamp-Meter. How about you? Do you use the 10A option or is it just there but never used?

Sincerely,
Hans

[rr100]

Take a look around you, many things use 1-10A.
What kills you doesn't matter, you can use real probes (with wires) not your fingers.

[Hans Gebert]

examples? I know that there are a lot of things using 1-10A..but nevertheless..nearly always its possible to measure with a clamp..perhaps i just haven't encountered the applications where current measurement in row is a must

[Harvs]

Dc current. It doesn't have to be mains voltage to use a dmm... I rarely use my meter for anything above 50v, just because that's not what I work with. In fact I use external shunts to get higher currents often.

[Achilles]

Well, split in two parts here I guess . If you're just into some electronics you're fine with an mA Range. I often needed the 10A range to check solar powered setups, so I don't want to miss that one.
Otherwise, you could use a transducer clamp for Amps (like the Metrahit Base) does, but that means more investment and something else to carry around. A meter without an 10A mode won't wander into my toolbag.....

EDIT:
My work is set-up and maintenance of research equipment in Meteorology/Climatology and remote sensing. So partly R&D and Electrician

[Hans Gebert]

Could you guys write down in which field you are working?

Examples R&D, HVAC, Electrician...that would help to understand if I miss anything..

[jnd]

For most of my measurements in low voltage electronics I need mA and A up to few amps. We got two the Agilent U1232A at work and when I compared them to the Fluke 117s which we have I was initially amazed by the number of features and noticed even the uA range. However there is no mA range! Microamps or amps, nothing in between... Fo some hobby project uA can be nice but I don't need it at work and what I was really missing from the Fluke 117 was the milliamps. I mean, even the cheapest meters have mA ranges, why not these? Are they trying to justify their higher models with this?

I agree that clamp meters are nice for fast current measurement however they're not that precise. We have one good PROVA model which can measure down to 400 mA DC range but these aren't cheap. One good thing is they don't have burden voltage. Which is another bad thing on the U1232A, you get about 300 mV per 100 uA which means nearly 2 V on full scale of 600 uA

[ejeffrey]

Hey all,
most Multimeters out there have different inputs for uA-measurements and measuremet above (10A).
I just wondered if the 10A option is really needed. 70mA can kill within milliseconds..So when I know that there will be currents above serveral mA I usually use my Clamp-Meter. How about you? Do you use the 10A option or is it just there but never used?

70 milliamps at 120 volts can kill.  Not so much at 10 volts that many of us prefer to work.  The current is there, but there simply isn't enough voltage to push it through your body.

Likewise, a 5 milliamp circuit at 120 volt is not something you should consider safe by any means.  Just because it only consumes 5 milliamp doesn't mean that the power supply can't drive 100 milliamp through your body.

[SeanB]

Measuring AC current I almost never use the 10a range on a meter, I use a clamp meter, mostly because in my case most of the measurements are over 10A, up to 200A. Mostly I use it on motors and to balance phase loads.

For Dc I will use the built in meter, as I do not currently have an AC/DC current probe ( but have not missed it too much for DC) and am looking for one cheap.

[rr100]

examples? I know that there are a lot of things using 1-10A..but nevertheless..nearly always its possible to measure with a clamp..perhaps i just haven't encountered the applications where current measurement in row is a must

Laptop, desktop, a few phones, most/all tablets, a decent torch or battery charger, some digital cameras. And probably many more.

Sometimes you can use a clamp meter for such things but more often than not you just don't get the precision you need. And I'm talking about VERY rough estimates. A crap 10 or 20A multimeter even with 2000 counts can read (if it has autoranging on that scale, most do): 15 mA or 147 mA or 1135 mA or 5.15 A or 15.24 A. When you read 2.1A on a good clamp meter you get at least a rough estimate, but how about when the device goes to sleep and you read 0.1A on the clamp meter? It can be in fact 15mA or 200mA. Or even zero! You can't just go with a multimeter on 200mA scale and see what's going on; apart from being inconvenient the device might wake up and go 1.5A and blow your fuse. And you also get a much higher voltage drop on the miliampermeter.

[Hans Gebert]

that sounds for me like..we need a multimeter that has the 10A Range + protection but can measure everything on this range..from uA, mA to A...

does something like this exist?

[Achilles]

I think the Metrix MTX-328x Series has just one Amps socket which is used for all.
Martin reviewed it once and is pretty happy with that fellow. The only thing I dislike is the clamshell design, otherwise it has really interesting features (one Amps socket, simultaneous A and V measurement, Math functions, graphical display, logging with timestamp, RTD temperature measurement)

[Hans Gebert]

The Mextrix device you mentioned seems pretty decent. It's pretty much what I searched for..you just can't misplace your probes in die A, uA, mA or V jacks. Thats an huge advantage..nevertheless the design is really ugly..

Edit: Votes without comments are half the fun

[Hans Gebert]

One more question that came just up to me:
Is there a meter with a good battery concept? Means the battery recharges when measuring voltage? Does something like this exist or can it even be realised?

[Harvs]

One more question that came just up to me:
Is there a meter with a good battery concept? Means the battery recharges when measuring voltage? Does something like this exist or can it even be realised?

The answer depends on what you mean.  If you're talking about recharging its own batteries off a voltage source it's measuring, then no.  The ideal multimeter has an infinite input impedance on the voltage ranges and an input imp of zero on current, so as not to effect whatever it's measuring.  What that means is you have zero input power to harvest.

If you're talking about recharging off a plug-pack, well yes you could, just like the fluke 196B scopemeter.  However it adds a lot of complication (which translates to cost) because it all needs to be isolated.  The second thing is the typical DMM can last quite a long time on a few AAs, so it's not going to be worth it.

[alm]

That meter would draw current from the circuit. It would have a very low input impedance and influence the circuit. It would be a really bad idea in all but a very limited set of circumstances. To charge an AA cell at 0.01C, it would require about 40 mW. This number would probably have to be even higher, since the average meter only spends a small amount of its time being connected to a voltage source. At 5 V, this 40 mW draw would represent an impedance of about 600 ohm. Measuring in digital circuits might easily introduce a 10+% error. Measuring in high-impedance circuits (eg. audio amplifiers with ~10kOhm input impedance) will be impossible.

I can also see fun stuff happening in mains circuits. You measure between live and earth. The meter draws just enough current to trip the GFCI/ELCB. That might make for one unhappy customer.

The Agilent U1253 OLED meter has a battery that can be recharged via a special power supply connected to the input jacks.

[Achilles]

The Agilent U1253 OLED meter has a battery that can be recharged via a special power supply connected to the input jacks.

well, it's not special....just a 24V DC source. You can also charge it with your lab powersupply set at 24V and plugging in 4mm Bananas in the GND and mA Jack. That 24V supply from the U1253B is pretty bulky, so most times I don't use it as a normal powersupply is on the table anyway.
You can only charge it when it's turned off, otherwise you'll blow the fuse.
Gossen Metrawatt has some Metrahit meters which have a DC jack. I have the same jack on my GMC calibrator. The manual states it won't charge, but power the meter. The Metrahit E Extra and Metrahit Energy uses that supply as well.

[Hans Gebert]

Some times has passed and I had time to watch Martins review concerning the Mextrix MTX-328x-Series.
Well it's not exactly the ideal device in my opinion..why does it have two 3 jacks..common, A and V...Why is there no meheter with just two jacks so you can't put your probes into the false input. That woulde be really great..never change the inputs..just select the function and..measure..I know it has someting to do with the internal architecuture of today's multimeters but well..couldn't this be changed somehow?!

[SeanB]

More to do with the cost of the switches. A switch that can both handle 10A, 1000v and at the same time not add extra contact resistance while handling millivolt signals is expensive, as well as not something which will be available in a mutipole rotary configuration. 3 sockets are a lot cheaper.

[c4757p]

Also, and more importantly IMHO, is that with separate jacks, if you switch modes with the probes attached, you usually won't blow anything (everything but the current modes is usually pretty robust). One accidental brush past A or mA with a single input and you pop your fuse or worse.

[Hans Gebert]

Well haven't so much fear about this one..Nowadays there are power electronics which could reduce if not prevent such accidents/blow ups.
But I understand the cost thing..rotary switch could stay but only for the selection of the function..not like now to change the circuits...alibi switch for all the guys used to it :E

[rsjsouza]

I know that there are a lot of things using 1-10A..

Sure there are... Even a simple AA battery gives a lot of current if connected to a small load, therefore the best practice is always to start on the high current range and then reduce to smaller levels. This is good practice when the current is unknown or can reach higher levels unexpectedly - examples would be tracking defects on equipment or if a short occurs when debugging a new project.

that sounds for me like..we need a multimeter that has the 10A Range + protection but can measure everything on this range..from uA, mA to A...
does something like this exist?

If you look at several of the older DMMs (Fluke 8020, for example), everything was integrated into the same input: from 200uA to 2A (Fluke 8060 is 10A). However, more modern DMMs with auto-range have the current inputs split between mA and A ranges because it is easier and simpler to maintain accuracy at the lowest ranges.

[PA4TIM]

If I use a meter to measure current it is pA to uA. Most times things like leakage. I have a pA meter and a spotgalvanometer for this sort of things. Sondtimes I use my Keithley or prema for this,

I allmost never use a multimeter for measuring higher current. I have an old fluke 8000 with 20 A option. This one I used one time adjusting the ampmeter of a battery charger/tester/dynamic load i designed.
For the rest i measure the voltdrop over a resistor allready in a circuit or I use a Tek P6042 AC/DC currentprobe, a clampmeter or a seperate shunt.

I think mistakes made in current measurenent is multimeter dead cause number one. ( the cheap not protected that are not fused in 10A and let you switch to voltage while the bananas are still in current busses

[rr100]

Some times has passed and I had time to watch Martins review concerning the Mextrix MTX-328x-Series.
Well it's not exactly the ideal device in my opinion..why does it have two 3 jacks..common, A and V...

Some time has passed and I ordered the "beastie". With 3 wires you can do V and A at the same time (yes, that's power, usually). And you can also log it! Big selling point.

Also even without dual function still for protection is best to have different wires. If you use the same wires it's just too easy to mess up your circuit by changing something on the meter and grounding by mistake whatever point you want to measure.

Well haven't so much fear about this one..Nowadays there are power electronics which could reduce if not prevent such accidents/blow ups.
But I understand the cost thing..rotary switch could stay but only for the selection of the function..not like now to change the circuits...alibi switch for all the guys used to it :E

The electronics might protect your meter but not the circuit you try to measure.

[Hans Gebert]

if it would be such a big prob for security..how can it be that for example fluke 116 measures Voltage and uA with only two jacks...no switching needed :E
if it works for small currents there has to be a possbility to do the same for larger currents..