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This is the cable coming from an SCT-013 current transformer current sensor. I don't understand the purpose of the bare wire strands that I have twisted and bent away from the rest of the two wires (they were previously all around the two wires).

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Are they important? If I need to connect this sensor to a microcontroller, what should I do with them?

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This is called the shield. It is designed to completely cover the other two wires. One end of the shield is connected to ground, and this effectively "shields" the other two wires from receiving RFI or EMI interference.

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  • \$\begingroup\$ Does the other end need to be connected somewhere as well? \$\endgroup\$ – Hassaan Mar 3 '16 at 13:30
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    \$\begingroup\$ It depends how the other end of the circuit gets its ground connection. If that's one of the other two wires or an entirely separate ground, you can (and may have to) leave the other end of the screen (shield) disconnected to prevent ground loops. But if there's no other ground connection, you can connect the screen and use it as your ground. \$\endgroup\$ – Brian Drummond Mar 3 '16 at 13:34
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    \$\begingroup\$ This screen is effective against electric fields, so it will attenuate capacitive coupling to voltage transitions. It is not effective against magnetic fields, so it will not stop electromagnetic induction. The effectiveness of the screen will reduce as the distance from the grounding point increases. This effect happens more quickly for higher frequency interference. For short cables, or for protection from low frequency coupling grounding at the processor end of the cable should be effective. \$\endgroup\$ – user1582568 Mar 3 '16 at 13:42

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