Remote moisture sensing utilizing ordinary RFID tags

Johan Sidén, Xuezhi Zeng, Tomas Unander, Andrey Koptyug, Hans Erik Nilsson

Research output: Chapter in Book/Report/Conference proceedingConference contribution

82 Citations (Scopus)


The paper presents a concept where pairs of ordinary RFID tags are exploited for use as remotely read moisture sensors. The pair of tags is incorporated into one label where one of the tags is embedded in a moisture absorbent material and the other is left open. In a humid environment the moisture concentration is higher in the absorbent material than the surrounding environment which causes degradation to the embedded tag's antenna in terms of dielectric losses and change of input impedance. The level of relative humidity or the amount of water in the absorbent material is determined for a passive RFID system by comparing the difference in RFID reader output power required to power up respectively the open and embedded tag. It is similarly shown how the backscattered signal strength of a semi-active RFID system is proportional to the relative humidity and amount of water in the absorbent material. Typical applications include moisture detection in buildings, especially from leaking water pipe connections hidden beyond walls. Presented solution has a cost comparable to ordinary RFID tags, and the passive system also has infinite life time since no internal power supply is needed. The concept is characterized for two commercial RFID systems, one passive operating at 868 MHz and one semi-active operating at 2.45 GHz.

Original languageEnglish
Title of host publicationThe 6th IEEE Conference on SENSORS, IEEE SENSORS 2007
Number of pages4
Publication statusPublished - 2007
Externally publishedYes
Event6th IEEE Conference on SENSORS, IEEE SENSORS 2007 - Atlanta, GA, United States
Duration: 28 Oct 200731 Oct 2007

Publication series

NameProceedings of IEEE Sensors


Conference6th IEEE Conference on SENSORS, IEEE SENSORS 2007
CountryUnited States
CityAtlanta, GA

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

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