SENSORS, 2002 IEEE

A local sensor bus for transmitting data from several digital smart sensors to an Internet interface was tested. The master/slave type bus is based on the three-wire SPI (serial peripheral interface) bus, which is built into most microcontrollers. At the sensor end, after A/D conversion of the analog sensor signals and further processing of the digitized data, the data is formatted into standard 8-byte ASCII code, which can be read directly by any computer. A header indicates the type of sensor data, for example, TC123.45 for a temperature sensor reading 123.45/spl deg/C. The data is in the form of an email so the following Internet interface (TCP/IP) only retransmits the data to the requesting browser where it is displayed in the same format as any email The Esbus format consists of an 8-byte request from the master followed by 32-byte response from the selected slave. The response is subdivided into an 8-byte header, which identifies the sensor and channel number, and three sets of 8-byte sensor data, as described above. In order to adapt the SPI an addressable network, the data output driver is converted to open collector. The paper will describe the I/O circuits, waveform/timing, and data formats for a specific smart sensor (temperature, humidity, illumination).

Many methods for fabricating structures for microfluidic-based sensors have been developed in recent years. However, little has been reported on effective methods for integrating these structures into electronic systems for analysis and fluidic delivery. This paper describes a straightforward and versatile fabrication platform for polymer microfluidics that readily accommodates integration with silicon-based sensors, printed circuit, and surface mount technologies. In particular, we have demonstrated a novel system for distributed fluid delivery to a flexural plate wave (FPW) chemical/biological sensor where micromachined fluidic components are combined in a single package with silicon die, multilayer printed circuit board, and surface mount electronics. In the same fabrication platform, we have demonstrated temperature control of the sensor with 0.1/spl deg/C precision using integrated metal thin-film heater and sensor elements. This is an important capability for FPW sensors to compensate for temperature-induced drift. We present results for the on-board microfluidic system where the sensor is used to detect changes in the composition of the supplied fluid.

A fractal analysis which takes into account the effect of surface heterogeneity brought about by ligand immobilization on the reaction kinetics is presented. The binding and dissociation of estrogen receptors ER/spl alpha/ and ER/spl beta/ to different ligands is analyzed within the fractal framework. The heterogeneity on the biosensor surface is made quantitative by using a single number, the fractal dimension, D/sub f/. The analysis provides physical insights into the binding of these receptors to different ligands and compounds, particularly the EDCs (endocrine disrupting compounds), which can have deleterious affects on humans and wildlife. Single- and dual-fractal models were employed to fit the ER binding data obtained from literature. Values of the binding and dissociation rate coefficient and fractal dimensions were obtained from a regression analysis provided by Corel Quattro Pro 8.0 (1997). In some cases both a single- and dual-fractal model was required to completely and adequately describe the kinetics involved. Values for the affinity, K/sub D/ (=k/sub d//k/sub a/) were also calculated. This provides us with some extra flexibility in designing biomolecular assays.

A gas sensor based on off-null ellipsometric readout is presented. It includes miniaturization of a null ellipsometer facilitating multisensing. and small optical components are used. Some experimental results on low concentration alcoholic gases (methanol, ethanol and 2-propanol) with porous silicon and chemically modified porous silicon as sensing layers are shown. Currently, the lower detection limit for these gases is about 1 ppm. Optimization of the sensor system and improvement of sensitivity or alteration of selectivity by modification of the sensing layer is also discussed.

We demonstrate a novel and simple sensor interrogation scheme for fiber Bragg grating (FBG) based sensing systems. In this scheme, a chirped FBG based Sagnac loop is used as a wavelength-dependent receiver, and a stable and linear readout response is realised. It is a significant advantage of this scheme that the sensitivity and the measurement wavelength range can be easily adjusted by controlling the chirp of the FBG or using an optical delay line in the Sagnac loop.

In this paper, we present an integrated AC current sensor based on sensitivity-optimised horizontal Hall effect devices (HHDs) and a differential readout chain. It has been designed for 5A nominal AC current measurement with 5 kV galvanic isolation and 0.5% accuracy over 1.5 kHz bandwidth, which allows up to 30/sup th/ (25 th) harmonic detection in 50 Hz (60 Hz) applications. From the sensing element to the instrumental chain's output the signal conditioning is exclusively performed by low-noise standard CMOS analog blocks. Moreover the whole microsystem features a mixed signal structure dedicated to auto-balancing.

Measuring distances, position and travel using the inductive proximity sensors (IPS) based on contactless target-approach detection is a widely used technique. In comparison to optical and capacitive technologies the biggest advantage of inductive sensors in industrial applications is the immunity against oil, water and dirt. In addition, current developments and trends in the industrial fields, especially micro-system and micromechanical applications like robotics and manipulator applications, require small, and fully integrated displacement and position sensors. The new series of Balluff sensors featuring new techniques and technologies, with single sensor calibration, improved accuracy and linearity; in addition excellent temperature stability is "the state of the art" in inductive sensors with complete integrated electronics. The paper includes the latest theoretical considerations and practical realizations about the miniaturized analog and binary inductive sensors for industrial applications, which at the same time show excellent electrical, mechanical and EMC-parameters.

A smart transducer network consists of a set of transducer nodes interconnected with a digital bus. Smart transducer technology implicates the development of systems supporting the timely exchange of real-time data. Additional requirements are support for system integration, mechanisms for dynamic reconfiguration, and diagnostic interfaces. Such systems should be composable and ease controlling system complexity, i.e. support the system engineer in understanding the system behavior Furthermore, developers expect diagnostic services, which are deterministic, reproducible, and do not interfere with real-time services. This paper describes three interfaces for smart transducer networks, which provide the required services while yielding the mentioned properties. We describe a case study demonstrating the effectiveness of the three interfaces for the proclaimed purpose.

The vacuum packaged differential resonant accelerometer (DRXL) using gap sensitive electrostatic change effect is proposed by using the reverse surface micromachining (RSM) process based on the single crystal silicon. The differential frequency output is achieved by subtracting the resonant frequency between the two independent resonators, which has advantages with the wide input range and the good linearity. But the resonant accelerometer is fabricated using the epi-polysilicon surface micromachining process in the previous work. The residual and shear stress of the polysilicon result in the mismatch of the mechanical resonant frequency. The mismatch of the resonant frequency may demolish the advantages of the differential scheme because of the mechanical resonance characteristics. So, the single-crystal silicon was chosen for the accelerometer structure material because it has better mechanical properties than the polysilicon. The fabricated resonant accelerometer shows the nominal frequency of 6928 Hz and the sensitivity is about 10Hz in the /spl plusmn/10 G range. The bandwidth is more than 100 Hz.

A micro integrated gas sensor array has been designed and fabricated with surface micro-machining technology. The sensor array consists of four elements integrated on a chip. Two different kinds of SnO/sub 2/ film were sputtered on the four sensors. Au and Pt were deposited on the surface of SnO/sub 2/ film as catalysts. The four sensors can be independently controlled by separate heater and temperature sensor. When implementing the function of electronic nose, the array can differentiate CO, NO/sub 2/ and H/sub 2/S and measure the concentration of each gas without the analysis of artificial neural network.