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Which are the guidelines for chose which cables should I twist as a pair? For example, suppose the case in which I have 3 cables. One of Vcc, one of GND and another of signal. Which ones should I twist? It would be better twisting signal+GND for better reference to signal (refereed to GND) or twisting GND+Vcc (for better decoupling)? Anyone may suggest good practices for twisting cables?

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With an unbalanced signal i.e. signal and ground rather than + & - signal wires, twisting the signal and ground will just couple more ground-wire current into your signal (by magnetic coupling). If this 0V current is power taken by some unspecified load then it will create interference.

At best it won't make a difference. At worse you could create a lot of noise on the signal and maybe even damage something. Best way with single-ended signals is to use coax.

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  • \$\begingroup\$ So, the best approach is, maybe, twist GND and Vcc and use a coaxial on signal? \$\endgroup\$ – Pedro Quadros Mar 11 '15 at 18:45
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    \$\begingroup\$ A good method is to use screened quad cable and drive the signal + & - and at the receiving end use a differential amp but you might get away with three wires twisted or untwisted. It's all about cable length, signal amplitude and frequency, potential interferers and possible ground fault currents from other equipment. It's actually quite a tricky subject. Quad cable has the four cores arranged in a diamond shape and power noise is equally induced on both cables but as you are trying to measure the differential, effectively there is zero noise theoretically. \$\endgroup\$ – Andy aka Mar 11 '15 at 18:50

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