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

Year: 2019

Authors: Demori M., Bau M., Dalola S., Ferrari M., Ferrari V.

Autors Affiliation: Univ Brescia, Dept Informat Engn, Via Branze 38, I-25123 Brescia, Italy; CNR, Natl Inst Opt, INO CNR, Via Branze 45, I-25123 Brescia, Italy.

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 k ohm-1.2 M ohm and capacitive elements in the range 200 pF-1.2 nF showing measurement resolution values of 1 k ohm 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.

Journal/Review: ELECTRONICS

Volume: 8 (6)      Pages from: 675-1  to: 675-15

KeyWords: low-frequency RFID; capacitive and resistive sensors; contactless interrogation; power transfer
DOI: 10.3390/electronics8060675

Citations: 8
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