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In using ADC how to discriminate between 2 sine wave with equal amplitudes and different polarity ( I mean 0 and 180 phases) ?

There is a sine wave that it's apmlitude is changed over the time and i want to track it for further processing ( it is not the case) . Unfortunately for every amplitude there are 2 phase ; 0 and 180 which it means for example there are Asin(wt) and -Asin(wt) and I want to detect this to different cases.

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  • \$\begingroup\$ ADCs take in analog and convert to digital. Your title is backwards. Two equal amplitude out of phase sine waves will cancel out to give you zero volts continuous. You need to edit your title and your question or it will be closed as "unclear what you are asking". \$\endgroup\$ – Transistor Jan 3 '18 at 14:13
  • \$\begingroup\$ Assuming you mean 2 different wires with incoming signals then you could use 2 ADCs with a high sample rate, but there's more to it than that when choosing an ADC. It really depends on what your goal is. Why not use a single ADC since when sig A is high, we know sig B is low (180 deg phase diff). Could you elaborate with more details for what you want to accomplish. \$\endgroup\$ – Klik Jan 3 '18 at 14:13
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    \$\begingroup\$ To discriminate two separate sine waves on different wires you can measure both several times provided you ADC is fast enough.What ADC are you using, does it have at least two channels and what frequency sine wave are you trying to measure? \$\endgroup\$ – Warren Hill Jan 3 '18 at 17:32
  • \$\begingroup\$ There was another question asked very close to your question: How to calculate phase shift between two sine wavefroms \$\endgroup\$ – Akshay Nachankar Jan 4 '18 at 10:35
  • \$\begingroup\$ It almost sounds like you're trying to decode BPSK but who knows. Not enough details here. \$\endgroup\$ – pipe Jan 4 '18 at 15:03
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If you only have the two sine wave inputs and no other reference there is no way to distinguish one from the other if one is 180° offset from the other.

On the other hand, if the phase difference is (say) 90° as in two-phase (quadrature) signals, you can tell the difference by simply looking at the other voltage when one crosses zero in a given direction.

enter image description here

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A summation amplifier will give a +2x if both input waveforms are the same. If one of the inputs has a 180 degree phase shift,then the sum will be zero.
... A simulation will exhibit a characteristic difference when the two identical sinusoids are used as inputs to a summing amplifier. The 180 degree phase shift appears to cancel out the total sine wave. ... giving a constant voltage with no variation.

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  • \$\begingroup\$ Thanks for your quick answer. But as I edited my question there is just one signal that chages over the time. \$\endgroup\$ – Abolfazl N Jan 4 '18 at 14:59

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