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High Current measurement using Arduino?

I need to measure Current from a welding machine to make a alarm if it goes down below some level for ensuring better quality.The current normally set is of the order of 200A max with around 100V DC.Not sure if i could use some clamp-on meters and decode the values. Shunt resistors may be a better option. But to make a signal conditioner to convert the ma output will be a problem i guess..is there something i can do with Arduino.. any ideas guys....?

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There are clamp on meter accessories for use with DMMs for about $50 that can measure hundreds of amps. The output is usually something like 1mV or 10mV per amp. The one I have can measure low frequency AC (less than 400Hz) and DC.

The clamp output could then be fed to an op amp for extra gain (if needed), followed by a comparator that would drive an output high or low when the current is out of the desired range.

Thats the most simple arrangement I can think of. If you can program any kind of micro then you could add a lot more smarts to it, otherwise the alarm would be going off every time the arc extinguishes.

rickharris5 years ago
You can buy clip on amper meters that have an external output to feed data to other things such as your micro.
What kind of welder is it ? If its an inverter type, you might be able to tap the information inside it anyway.

For 200A, I'd be inclined to use a hall-effect sensor.

Steve
Use a shunt resistor and a voltage meter. A 1 ohm shunt will read 1mV for every amp going through the shunt. You can get a simple panel meter and mod it into the face of the welder.
...and will dissipate 40kW !!!!

A 1 ohm resistor will read 1 volt for every amp. Perhaps you meant a 1mOhm resistor ?