Sampling question in PI design

[scrungy_doolittle]

Are you referring to the max usable res of 13bit? I have read this, which would imply making sure you use A10 and A110 diferentially to achieve 16bit.

My personal choice would be PIC24FJ128GC010. It has a 16 bit adc with a 66K sample rate, and a 12 bit 10 MEGASAMPLES per second, with hardware oversampling, and dma. Plus some built in co
mparators and opamps. The other one, and one I more or less chose for a PI detector project that I had to drop for now, is a ST32F411 That one has a 2 mega samples 12 bit. and DMA. And a 98 mhz cortex. There are ways to achieve more resolution, and
the pic auto-oversample is nice. My idea is to sample 360 times per cycle, and then your phase angles are just indexes into the buffer. So you can do standard ground balance, and relationship computations. Basically, you sample the transmit wave form, (or generate it and make a copy), and sample the recieve waveform at the same time. i.e. interleave samples. then it becomes trivial to
extract phase shifts, to select a portion of the received form based on the transmit etc. Instead of generating sample windows, with phase shifters like the analog whites detectors, and generating a sample
at the peak of the recieve signal, one just can add up the data. so for example, if you know where the top of the sine wave is, you can determine the phase shift of the received signal sinewave. you can
also pick any sample point, and grab data around it. For example, if you have 360 samples per cycle, then buffer[180] is the zero point, etc. You might want to google DC42 on github for an arduino project. There is a nice expired whites patent that describes ground balancing with smaller samples, and this, and a current patent that explains it quite clearly But this is old prior art as well. Basically you can ground balance any given point, by taking two other points. 486890 is the patent that covered the Eagle also has lots of information. I'm trying to remember the details, but one patent explains how, given 3 samples P1,P2 and P3, you can compute a ground balance by adding two of them and dividing by the negative reciprical of the third or something similar. Large gain preamps, and fast sampling will give you digitized transmit and receive waveforms, and then you can apply any sampling you want to. Want phase angle 45? add points 41-48 and divide 8 and you will get the "voltage" level that a sampling window of 8 degrees wide would give you. Other useful patents are. 514815 US 5523690 57291489 (which is a 1998 patent that should just be expiring after 17 years).O