Impedius: A Signal-Space Multiplexing Technique Using Individual Elements of Impedance for Chained Passive Sensors

Commercial touch input devices sense changes in capacitance (C), resistance (R), and inductance (L), but aggregate these into a single, complex quantity: impedance. Commercially available LCR meters, however, can report the individual elements of impedance. We use this capability to introduce Impedius, a signal-space multiplexing technique. With Impedius, we create and sense multiple static values and continuous changes in the R and C values within a single circuit by manipulating capacitance and resistance individually. Further, we explore 3D printing as a method to create predictable resistance and capacitance values via geometric and printer setting manipulation, and offer a software tool that generates components with desired R and C values. Based on 96 samples, our printed passive components have error μ = 4.63 pF, ο = 1.68 PF (capacitors) and μ = 13.85 kΩ, ο = 5.59 kΩ (resistors). We demonstrate multiple interactive example applications with our components, highlighting the opportunities for signal-space multiplexing.