Hi guys, long time no see :-D
So, after a long while I have finally finished one of my projects - a new method for measuring lots of resistors ( N*(N-1)/2 ) using only N wires! This means that with 8 wires you can measure up to 28 resistors/resistive sensors. With 16 wires this could be 120 resistors... minus a few reference resistors :-) The application range is a very niche area, where you are extremely constrained by the physical size or cost of extra cabling, such as a microscopic probe with thermistors along its length, or similar.
In summary, the method uses a mesh of resistors, connected between N nodes where every node is connected to every other node with a maximum of one resistor - topologically, a complete graph, as shown in the attachment. The measurement system connects the nodes to either one of the at least two excitation voltages (the simplest being GND and VCC) or floats that node. This limits the scope of any one measurement, allowing the creation of a single linear equation describing that particular situation. With enough of the measured combinations (I call them situations), and an addition of special equations describing the reference resistors, an overdetermined system of linear equations can be formed, and solved iteratively. And that's that :-)
The method works, has been tried both in simulation and on a real device. And that device is of course an AVR ATMega32 :-)
For more details, see the write up on my page:
Theory start: http://www.daqq.eu/?p=1333
Theory continuation: http://www.daqq.eu/?p=1412
Practical implementation: http://www.daqq.eu/?p=1676
Coming soon: Software, firmware descriptions and detailed results.