Stanislav Ivanov

A miniature, low cost CTD system for coastal salinity measurements

In this work we describe a small, low cost conductivity, temperature and depth (CTD) system for measurements of salinity in coastal waters. The system incorporates three low cost expendable sensors, a novel planar four-electrode conductivity cell, a planar resistive temperature device and a piezoelectric pressure sensor. The conductivity cell and the resistive temperature device were fabricated using novel printed circuit board (PCB) microelectromechanical (MEMS) techniques combined with a new thin-film material, liquid crystal polymer (LCP). Printed circuit board techniques allow for mass production of the sensors, thereby lowering the cost of the system. The three sensors are packaged so that they are independent of one another and can be quickly replaced if bio-fouled or damaged. Deployments in Bayboro Harbor, St Petersburg, FL demonstrate that the novel CTD systems are capable of obtaining highly resolved in situ salinity measurements comparable to measurements obtained using commercially available instruments. The estimated accuracies for the conductivity, temperature and pressure sensors are ±1.47%, ±0.546 °C and ±0.02 bar, respectively. This work indicates that a small, low cost CTD system with expendable/replaceable sensors can be used to provide accurate, precise and highly resolved conductivity, temperature and pressure measurements in a coastal environment.

Distributed Enviromental Sensor Network: Design and Experiments

Algorithms for sensor deployment and adaptive sampling form the basis for multisensor fusion of spatio-temporal data from a wireless environmental network of deployed sensors. Derivation of sampling algorithms based on parametric methods are described. These algorithms form the basis for deployment of an array of wireless CTD (conductivity, temperature, depth) sensors to observe basic oceanographic data in Tampa Bay, Florida, USA. This distributed sensor network communicates using RF wireless 802.11b systems, and provides data in real-time to a shore observation station. In the experiments described here, five CTD sensors recorded reliable data over 25 hours. These data have been analyzed using multisensor fusion algorithms to characterize the temporal and spatial patterns. The resulting data analysis is available for integration with other observations made during these experiments, including biological and chemical variables. The approach demonstrates the ability to design and deploy a distributed sensor network that monitors real-time spatio-temporal oceanographic data, and supports further deployments that will incorporate mobile nodes capable of adaptive reconfiguration

PCB-MEMS Environmental Sensors in the Field

Sensor networks for in-water measurements using Organic MEMS are progressing in our research effort. PCBMEMS enabled systems, primarily in Liquid Crystal Polymer material (LCP) have emerged from the laboratory and are operational in the field. The latest progress in sensor development has yielded PCBMEMS sensors operating in the field for extended periods. In addition, we have developed the multisensor system that measures conductivity, temperature, and pressure, and combined it with a 3D system-in-package wireless module based on the 802.11b protocol to create a salinity network node and an environmental network system. The power consumption, reliability and fouling of the fieldable sensors have been evaluated. Our results indicate that biofouling has become the limiting factor for sustained performance of the multisensor system within the environment.