Low-Frequency RFID Signal and Power Transfer Circuitry for Capacitive and Resistive Mixed Sensor Array

Abstract

This paper presents a contactless measurement system for a mixed array of resistive and capacitive sensors exploiting a low-frequency radio-frequency identification (RFID)-based approach. The system is composed of a reader unit which provides power to and exchanges measurement data with a battery-less sensor unit. The sensor unit is based on a transponder operating at 134.2 kHz and a microcontroller. The microcontroller sequentially measures the elements of the sensor array composed of n capacitive and m resistive sensors which share a common terminal. The adopted technique measures the charging time of a resistor–capacitor (RC) circuit, where the resistor or the capacitor can be either the sensing element or a reference component. With the proposed approach, the measured values of the resistive or capacitive elements of the sensor array are first-order independent from the supply voltage level. A prototype has been developed and experimentally tested with resistive elements in the range 400 kΩ–1.2 MΩ and capacitive elements in the range 200 pF–1.2 nF showing measurement resolution values of 1 kΩ and 5 pF, respectively. Operative distances up to 3 cm have been achieved, with readings taken faster than one element of the array per second.

A flexible pressure sensor with interference immunity capability

“…Flexible sensor arrays are increasingly being used for various applications involving wearable devices and reconfiguration of sensory functions. According to response principles, flexible sensor arrays can be mainly divided into resistive type (Gong et al, 2021;Ghosh et al, 2020;Yue and Moussa, 2018), piezoelectric type (Wang et al, 2021a(Wang et al, , 2021b(Wang et al, , 2021cTian et al, 2020;Lin et al, 2021), capacitive type (Marco et al, 2019;Sotgiu et al, 2020;Wang et al, 2022;Ye et al, 2018) and friction power generation type (Liu et al, 2017a(Liu et al, , 2017bWang et al, 2019;Shohag et al, 2018). It is worth noting that sensor arrays sharing the same substrate inevitably induce mutual influence.…”

Design of a low-frequency miniaturized piezoelectric antenna based on acoustically actuated principle

“…Low frequency (LF) antenna has been widely used in meteorological broadcast, radio navigation, radio frequency identification, and underwater communication because of its high penetrability and low attenuation rate. [1][2][3][4][5] The LF antenna has longer wavelength (1 km-10 km) than the high-frequency antenna, its transmission loss is not sensitive to water, nor rock, nor soil, and it has excellent penetrability and long-distance transmission performance. Therefore, the LF antenna is suitable for underwater communication and object detection in rocks and soil.…”

Experimental study on the power consumption of timers embedded into microcontrollers

“…an oscillator) that also provide a time-modulated output signal [4]. A particular case of that is the concept of direct sensor-to-MCU interface circuit, where the MCU excites the sensor and this provides a time-modulated signal with information about the resistance [5], [6], capacitance [7], [8], or inductance [9], [10] of the sensor, as represented in Fig. 1(b).…”