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low cost high current sensing ?

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seyyah

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How can we measure a dc current of 20A accurute enough but costs low? I thought to use a conductor piece. I think brass conductors are used for this. But i don't know how to obtain this conductor's resistance. Can you suggest me something?
 

why not to use a resistor? you can take some low-ohmic resistor(smd or through hole), 0.01Ohm with Kelvin connection.
 

Hmm. I once asked for 0.01 resistors but they were expensive. I think made by aluminium. After that i didn't search for resistor and believed that below 0.1 ohm resistors are expensive :) I think there are proper resistors. By the way what did you mean by kelvin connection?
 

Hall current sensor is not so expensive. Of course the price is higher than a resistor
 

Kelvin connection - the rersistor has four terminals, two for the current path, two for the measurement circuit. By this you can eliminate voltage drop across the wires of the measurement circuit.
And the cost of such a resistor is not so high - 0.01Ohm, 1W, 5% SMD resitor costs $0.7
 

You can use a length of copper wire but temperature coeficiant will be more.
You can also use "manganin" wire
 

How can we measure a dc current of 20A accurute enough but costs low? I thought to use a conductor piece. I think brass conductors are used for this. But i don't know how to obtain this conductor's resistance. Can you suggest me something?
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Use iron, brass, or copper about 10cm, so measure with high precision ohmmmeter. if no have, you can measure it with high current and measure with voltmeter on end point. example with 20A, so if volt=2V the resistance is 2/20 = 0,1Ohm
 

Actually i used brass wire but it's difficult to shape it and it's dificult to find its resistance. Known resistor would be more practical and accurate. I think brass is more stable against temperature than iron and copper.
 

HI

Search Zetex site thay have app note on how to design sesing resistor on a PCB

www.zetex.com

All the best

Bobi
 

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