How to measure extra high current (more then 1000A)

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#1
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Hello all,

My clamp meter is limited up to 600A
My last attemp measure current stops on 1230A / 3V and it was analog current clamp meter.

( if you want to known what the hell I am trying to do - I am trying repair spot-welder and calibrate ranges on front pannel which was damaged)

My new clamp meter will arrive into my location in 6-8weeks.(I hate this waitting)

From this reason I wish to make tempovery current meter from discrete parts (they are available in local DIY store)

I am able measure current with shunt resistor but I never measured so high current as I need now.
Could anyone help with any idea howto measure this current? I dont need high accuracy only to known how much flow over my 10mm (diameter cables to eletrodes TIG/1.6mm Cu-prum is melting very fast)

Howto implement Peak&Hold function ?

Thanks

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A ballistic galvanometer gives you enough time to make a reading. Make from a magnetic compass at a suitable distance, and calibrate with a known charge.

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I've never worked with a TIG welder.

That said, while awaiting your new ammeter, would it be possible to measure the current on the INPUT to the power supply, instead of measuring the current on the output?

I don't know how TIG power supplies are designed, and hence their efficiency. But power into the system has to equal power output from the system.

JC

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Well I not explained good my situation and what I want to do.

I am using classic arc spot-welder method.

I am damaged cuprum eletrodes very fast so I exchanged it with tungsten rods (they are not melding so fast)

I need only to known how measure so high current without clamp meter.

Becouse I need make marks on meter scale.

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Quote:
My clamp meter is limited up to 600A

Then strip part of the wire and clamp on half of the threads.

No RSTDISBL, no fun!

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Quote:

Then strip part of the wire and clamp on half of the threads.

@Brutte> could you explain how you mean this?

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The wire is stranded so if 1000A runs through all tiny wires then 500A runs through half of them and 500A runs through the other half.

No RSTDISBL, no fun!

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Brilliant !

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tessa and Tina, You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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Another way is to use a large toroid core, one turn at 1000A, measure current on separate 2 turn winding, ends connected with clamp-on.

Brutte has a better solution, meter both strand pairs and sum.

It all starts with a mental vision.

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Brutte wrote:
The wire is stranded so if 1000A runs through all tiny wires then 500A runs through half of them and 500A runs through the other half.

Do you know if this is actually true?

It seems to me that the current flowing through a multi-strand wire--especially if it's been separated into two groups with an inductive load placed on one of those groups--is not necessarily this uniform. I have no idea how big a difference there is, but would hesitate to assume uniform current flow through the strands unless I knew it to be the case.

Michael

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With the relatively small inductances that show up and the relatively low frequency (AC power line), it should not be a problem.

Probably more significant is that the current probe will inject a small apparent series resistance into the part being tested, and that will shift some of the current to the other part. However, the effect should be small and something like a welder would likely continue to operate as it did.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Quote:
with an inductive load placed on one of those groups

Yes, each U/I metering device has some nonzero impedance. And any measurement influences the circuit some way. But usually the measuring device is made so that influence of a measurement is neglected (or at least known and the skewed result is corrected).

No RSTDISBL, no fun!

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Perhaps measure the voltage drop over 1 meter of the wire (or so).

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Quote:
Perhaps measure the voltage drop over 1 meter of the wire (or so).

Or force acting on those wires. Then you do not need to know what these are made of.

No RSTDISBL, no fun!

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ka7ehk wrote:
With the relatively small inductances that show up and the relatively low frequency (AC power line), it should not be a problem.

Maybe not an issue for the OP's spot welder, but modern AC TIG machines produce square waves at up to 400Hz. Whether the cumulative impedance of cables, electrode, arc, and workpiece leave the current waveform looking anything like a square wave I can't really say, but I would assume that there are still some higher-frequency components left in it.

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It's nice to see discussion continue.
I solved my problem with measuring current simple my clamp-meter came yesterday much earlier I think :)

I want to known if I have cheap clamp-meter without TrueRMS function if my measuremt will be much more different as measuring with TrueRMS feature? or other question when
is TrueRMS feature really valuable.

About spot welder project.
I found my eletrodes from Tungsten/Volfram with diameter 1.6mm was not the best choice.
It's holding fine they are not damaging as eletrodes before.
but conductivity is not good.

Cuprum       1.68e-8
Aluminium    2,82e-8
Tungsten     5.28e-8   (volfram)
Nickel       6.99e-8
Silver eletrodes are best but most expensive :lol:

but I need really cuprum eletrodes
I can weld with existing setup only razor blades but nothing else nothing fatter when 0.3mm to 0.5mm. Everything else is only burn. I hope I will find better thin electrodes and I will be able spot-weld battery tabs for my new accupack soon 8)

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Another method would be to use a Rowgoski coil. There is even a project here for one.

https://www.avrfreaks.net/index.p...

Cheers,

Ross

Ross McKenzie ValuSoft Melbourne Australia

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Quote:
I want to known if I have cheap clamp-meter without TrueRMS function if my measuremt will be much more different as measuring with TrueRMS feature? or other question when
is TrueRMS feature really valuable.

If you're measuring DC, trueRMS doesn't come into it. If you are measuring AC and especially non sinusoidal AC, then you really want trueRMS.

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Kartman wrote:
Quote:
TrueRMS function if my measuremt will be much more different as measuring with TrueRMS feature? or other question when
is TrueRMS feature really valuable.

If you're measuring DC, trueRMS doesn't come into it. If you are measuring AC and especially non sinusoidal AC, then you really want trueRMS.

Thank's for your reply.
So when I will measure only AC 220/50hz is not TrueRMS feature required. But DMMs with this feature can provide much more better results.

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Depends on the load. Anything other than an incandescent light bulb may give rise to measurement errors. You might want to Google rms to understand the implication.