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First off, please forgive me if this is the worst design ever. I am just learning with experience.

Here is a design for an AC current measurement

schematic

simulate this circuit – Schematic created using CircuitLab

I was following the article put forward by LT themselves. On LTSpice i get the same voltage as the input but i wanted a second opinion before i purchase the components. As a beginner to Opamps i can understand the article but not sure if my design is correct.

Thanks in advance.

George
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    R1 is 300uOhms, that so low, you'd need a super conductor and liquid nitrogen to get that low. Actually R1 is rather pointless, you might want to simply remove it. Use google to search for the free ebook "Opamps for everyone" to learn more about opamps. The design from LT looks fine to me. If you build it like that it should just work. – Bimpelrekkie Sep 26 '17 at 20:56
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    You're not thinking of connecting R1 to the mains, by any chance? (This would be the start of a bad day.) i.e., What is V1. Also note that R1 is pretty much a dead-short across V1. Add a bit more information to your post about your ultimate goal. – Transistor Sep 26 '17 at 21:00
  • the goal here is to measure how much current has been put out during a spot weld, the low resistance 300uOhm is the section of the weld cable which 3vac at open circuit. A discussion of the same is [here](https://forum.allaboutcircuits.com/threads/measure-high-ac-current-with-an-arduino.140337/page-3) – George Sep 26 '17 at 22:12
  • Just added fig 2 with another design. – George Sep 27 '17 at 07:03
  • It would be far more safe to measure current indirectly using a Hall sensor. See my answer to [measuring current](https://electronics.stackexchange.com/questions/247259/measuring-current-in-combination-circuit-with-a-shunt/247263#247263) for some ideas on this. – Transistor Sep 27 '17 at 07:24
  • Thank you Transistor. I understand the safety but for this project to measure 3000A would not be ideal, or would it be possible ? – George Sep 27 '17 at 10:04

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