Embedded Wideband Measurement System for Fast Impedance Spectroscopy Using Undersampling

Embedded impedance spectroscopy is gaining importance in the Internet of Things (IoT) era, where a new class of impedance spectroscopy devices is needed to fulfill a suitable frequency range, size, power consumption, and costs. In this paper, we investigate the feasibility of embedded impedance spectroscopy measurement systems with a focus on power-aware systems. We propose a novel embedded architecture based on a low-cost microcontroller and using a reduced number of electronic components. In order to enable the system for measuring higher frequencies up to 10 MHz, we use the undersampling technique on a relatively simple microcontroller with 12-bit inbuilt analog-to-digital converters and a sampling rate of 1 mega samples per seconds (MSPs). For the impedance calculation in the range of 100 Ω-1 MQ, the Discrete Fourier Transform (DFT) is implemented directly on the same microcontroller. The experimental validation shows a maximal standard deviation of 0.5% in amplitude measurement and a standard deviation of 0.55° in phase measurement, which are sufficient for various applications of wearable solutions. The system design provides an outstanding performance considering low-cost, small foot print, and low-power consumption.