4-wire resistance measurements

I think the resistance measurements would be much more accurate and useful if a Kelvin connection was employed to tap off the dV at the PPC side while under stimulus from one of the fixed current sources. This should allow for much more accurate resistance measurements up to 300kΩ without as much contribution from the cabling, muxing, and so on. The voltage could be tapped off at ADG0/ADG1 and measured differentially so that only the series R of the RATPxx mux (which is much smaller, more predictable, and has good flatness between channels) affects the measurement.