2.?Wireless Corrosion Monitoring Sensor and NetworkCompared with the traditional corrosion monitoring approaches, wireless technology-based monitoring is very efficient in terms of cost, convenience, and human-operation overhead, and thus has attracted much attention in the past few years. In this work, we design a WSN to monitor the corrosion of RC structures. The advantages of our WSN-based test-beds are as follows. First, the designed corrosion-detecting device can be built using commercial off-the-shelf wireless motes, such as the Crossbow Mica mote and the Berkeley Telosb mote, so the hardware costs are very low, and the network is easily extended. Second, once the corrosion-detecting device is attached to the wireless mote, we can control the sampling rate by dynamically setting its parameters in an over-the-air fashion.
2.1. Corrosion-Detecting Sensor Mote DesignIn designing the corrosion sensing mote platform, we have to address the following three problems: (1) what sensing device will be used in corrosion signal detection, (2) which kind of wireless mote is appropriate for our objectives in terms of cost and extensibility, and (3) how to connect the corrosion-detecting device to the wireless mote. We will present the designed corrosion-detecting devices in the later sections. Next, we will introduce the MicaZ mote in use and the designed circuit connecting the corrosion-detecting device with the MicaZ mote.As a general wireless embedded platform, the MicaZ mote can not only measure 0�C3 V with 0.01 mV resolution, but also be extended to monitor diverse other signals (such as temperature, humidity and vibration, etc.
), so we used the MicaZ mote in our test-bed to support a closer monitoring of corrosion of RC structures. In our design, we consider mainly two issues related to the WSN platform: one is how to connect the corrosion-detection device to the MicaZ mote, and the other one is how to implement a wireless communication algorithm to effectively Batimastat collect the corrosion data. Figure 1 shows the architecture of our test-bed. The sensing layer consists of a set of sensor motes, which will self-organize into a wireless network. The laptop, data server, or other Internet-accessing devices belong to the gateway layer which is responsible for collecting all the data sent by the sensing layer.
The back-end application layer provides a visual interface for users as well as domain experts. As long as users can access the Internet, they can browse the data and the corresponding analysis results, or even download them.Figure 1.The architecture of the wireless corrosion monitoring system.Even though the MicaZ mote is fitted with a 51-pin connector for external sensing devices, it cannot directly read the signal output of our corrosion-detection devices. This is because MicaZ’s analog-to-digital conversion (ADC) interface (channel) cannot directly measure the current.