Sensors and Actuators B 102 (2004) 27–34 A miniaturized low-power wireless remote environmental monitoring system based on electrochemical analysis Kwang-Seok Yun a , Joonho Gil a , Jinbong Kim a , Hong-Jeong Kim b , Kyunghyun Kim a , Daesik Park a , Myeung su Kim a , Hyungcheol Shin a , Kwyro Lee a , Juhyoun Kwak b , Euisik Yoon a,∗ a Division of Electrical Engineering, Department of Electrical Engineering and Computer Science, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, South Korea b Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, South Korea Received 1 July 2003; received in revised form 4 November 2003; accepted 11 November 2003 Available online 21 January 2004 Abstract In this paper, we report a miniaturized low-power wireless remote environmental monitoring system. This system has been developed for on-site monitoring of water pollution by heavy-metal ions. The system is composed of three parts: an electrochemical sensor module using microfabricated electrodes for detecting heavy-metal contamination in sample water; a custom potentiostat module including readout circuitry, analog-to-digital converter and microcontroller; and a radio frequency (RF) module for sending detected signals to a base station through wireless communication. The electrochemical sensor module is implemented using microfabricated mercury working electrodes (WEs), solid-state reference electrode (SSRE), and platinum counter electrode (CE). For the low-power operation, direct frequency-shift keying (FSK) modulation and simple binary FSK demodulation methods are used for RF module which is realized using 0.18 m CMOS technology. All the modules are hybrid integrated in a printed circuit board (PCB) and low-power consumption below 1mW has been achieved. © 2003 Elsevier B.V. All rights reserved. Keywords: Environmental sensor; Heavy-metal ion; Low power; Microsensor; Sensor network; Wireless sensor 1. Introduction As the contamination of groundwater by heavy-metal ions is critically harmful to many organisms, including hu- mans, there have been various researches and reports on in situ and on-site detection of heavy-metal contaminants using electrochemical detection methods [1–5]. Electro- chemical detection can be easily realized in a simple and cheap implementation platform with high sensitivity and its implementation is quite compatible with conventional semiconductor processing technologies. The previous ap- proaches have used electrochemical sensor integrated with a custom designed potentiostat for simple on-site analysis system. However, they have used a laptop computer for data acquisition, signal processing, and system control, and this makes it difficult to achieve periodic on-site environmental monitoring in broad field areas. ∗ Corresponding author. Tel.: +82-42-869-3462; fax: +82-42-869-3410. E-mail address: esyoon@ee.kaist.ac.kr (E. Yoon). In this paper, we have proposed and implemented the miniaturized wireless remote environmental monitoring sys- tem. This system monitors water pollution of heavy-metal ions by using electrochemical detection and wirelessly trans- mits the detected signal to a base station. As for wireless communications, we have adopted a low-power distributed wireless network scheme [6–9]. The proposed environmental monitoring system includes sensing electrodes, potentiostat, and radio frequency (RF) communication module with an antenna and can be located in broad open fields such as river, coast, etc. When the analysis is requested by the base station, heavy-metal ions in the water are analyzed by the electro- chemical sensor with potentiostat and the detected signals are transferred to the base station through the RF module. There are some requirements for the proposed wireless monitoring system. In order to realize a miniaturized sys- tem, all the important components for the proposed sensor system should be integrated in a small form factor. Also, as a distributed portable system, the entire components must be optimally designed to reduce the power consumption. In 0925-4005/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2003.11.008