A Hydrogen Concentration Monitoring System With Passive Tags

This article describes the design of a hydrogen concentration monitoring system based on ultrahigh-frequency radio-frequency identification (RFID) passive tags, which adopts ISO/IEC 18000-6 Type C standard. Tag devices have been designed by employing a microcontrol unit, making the proposed solution very suitable for low-cost hydrogen concentration measurement in wireless sensor networks. Furthermore, anti-collision capability has been realized by implementing a new true random number generator based on the hydrogen concentration sensing circuit and analog-to-digital converter, 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 an 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%.