:56361186 About the right leg circuit, I remember the first article I read about the 10 lead ECG is based on the Einthoven Triangle - Wikipedia https://en.wikipedia.org/wiki/Einthoven%27s_triangle. The very clever guy invented this triangle the late 1800's, and got a Nobel prize in medicine. I remember I spent a couple of hours clarifying the basic things, and explain to a medi guy how the triangle works, and how to memorize the meaning of the names of the 10 leads. One thing I was very impressed is the following: The 12 leads are placed on the serface of the body, but what is interpreted is the heart inside the body. In other words, 2D measurement can be transformed to that of the 3D object surrounded by the cylinder surface. The mathematics is very involved, and I gave up reading to the middle of the proof, because I guess it might take me at least 3 hours to go through the lengthy maths proof. Now the OP using AD5933 is very roughly similar: wraps some 8 sensors around the forearm and get the cross section of the muscle operation. I am hoping to follow the CMU TOMO paper and doing something similar. So you see, I am kwilling two birds with one stone: AD5933 can sense forearm muscle cross section stuff, but can also measure the tunnel diode's resistance and inductance, ..