A Hydrogen Concentration Monitoring System with Passive Tags

This paper describes the design of a hydrogen concentration monitoring system based on ultra-high frequency (UHF) radio frequency identification (RFID) passive tags which adopts ISO/IEC 18000-6 Type C standard. Tag devices have been designed by employing a micro-control unit (MCU), making the proposed solution very suitable for low-cost hydrogen concentration measurement in wireless sensor networks (WSNs). Furthermore, anti-collision capability has been realized by implementing a new true random number generator (TRNG) based on hydrogen concentration sensing circuit and analog-to-digital converter (ADC), without employing any additional device. The correctness of all operations of the RFID system has been experimentally verified in a multiple-tag environment, as well as the hydrogen concentration monitoring capability. Particularly, measurement on a RFID tag prototype developed for the bandwidth 920-925 MHz has revealed that when the ambient temperature is 25 ∘C and humidity 80%, a maximum error of 9.8% is found within a hydrogen concentration range from 0.24% to 2.4%.