SENSORS, 2002 IEEE

The basic principles of a new surface acoustic wave (SAW) gas sensor are described. Being essentially a sensor of the mass-sensitive type, the proposed device possesses certain features of the thermometric SAW sensors and is not only sensitive to the vapors of volatile substances, but capable of detecting gases by their thermal properties as well. This principles consists of making a certain delay of heat fluxes between the substrate of sensitive SAW element (SAW delay line or SAW resonator) and working surface of the sensor's temperature stabilization system. In contrast to the known thermometric SAW sensors, the proposed sensor is characterized by high temperature stability and fast response. A variant of the sensor based on a LiNbO/sub 3/ is described and some results on detecting propane-butane mixtures are presented, glass spacers being a means providing heat flux delay between LiNbO/sub 3/ substrate and working surface of the sensor's temperature stabilization system.

Trong nghiên cứu này, các điện trở nhiệt dựa trên cấu trúc hình chữ nhật đơn giản được chế tạo trên ba loại nền phim mỏng (0,1 /spl mu/m) silicon trên cách điện (SOI), phim dày (10 /spl mu/m) SOI và silicon khối, và các đặc tính của chúng được điều tra. Các phép đo xác nhận rằng SOI thực sự có thể cung cấp thêm tự do để tăng nhiệt độ tối đa hoạt động (T/sub max/). Quan trọng hơn, điện trở nhiệt SOI phim mỏng không chỉ đạt được T/sub max/ lên đến 420/spl deg/C, mà còn có dòng hoạt động thấp chỉ 1 /spl mu/A, nhỏ hơn khoảng 1.000 lần so với điện trở nhiệt SOI phim dày tương đương tại cùng một T/sub max/. Kết luận, điện trở silicon trên SOI là một cảm biến nhiệt có chi phí thấp đầy hứa hẹn cho một loạt các ứng dụng nhiệt độ cao yêu cầu công suất thấp.

Trace level detection of H/sub 2/S is of immense interest in diverse fields ranging from gas and oil exploration to dentistry. In the present work 0.12 /spl mu/m thick sputtered SnO/sub 2/ films, and a novel SnO/sub 2/-CuO bilayer structure consisting of ultra thin (/spl sim/10 nm) CuO dotted islands (0.6 mm diameter) are investigated for H/sub 2/S gas sensing. With the SnO/sub 2/-CuO-dotted sensor, a high sensitivity of 7.3/spl times/10/sup 3/ at a low operating temperature of 150/spl deg/C is obtained with a fast response time of 14 seconds for 20 ppm of H/sub 2/S gas and a recovery time of 118 seconds under flowing air have been measured. The electronic and chemical interactions of the CuO catalyst layer on SnO/sub 2/ in the presence of H/sub 2/S have been analyzed in the light of space charge regions formed due to distributed p-type CuO islands on the n-type SnO/sub 2/ thin film surface. Dissociated hydrogen available from the CuO-H/sub 2/S interaction spills over and is found to be primarily responsible for the observed fast response characteristics.

Reports recent work on thick film permalloy (NiFe) and NiCo alloy anisotropic magnetoresistive sensors made by thermal spray. Various sensor layouts have been fabricated and characterized. The AMR effect of 2.45% and 2.68% is obtained in as-sprayed permalloy and NiCo alloy sensors. Resistivity of thermal sprayed thick film is 40-60 /spl mu//spl Omega/-cm, which is higher than bulk material. A maximum /spl Delta/R/R value of 5.2% is achieved after thermal annealing. A high /spl Delta/R/R value and low saturation fields are the important features of thermal spray sensors. The very promising results demonstrate the potential applications of thermal spray sensors.

This paper presents a novel ultrasonic sensing system for autonomous mobile systems. We describe how wide-angled ultrasonic transducers can be used to obtain substantial information on the environment. This can be achieved by exploiting the overlapping of the detection cones from neighboring sensors. The ultrasonic sensing system also allows the detection of multiple echoes from different echo paths for each sensor. In this way a significantly higher number of echoes can be obtained in comparison to conventional ultrasonic sensing systems for mobile robots. In order to benefit from the increased sensor information, adequate data post-processing is required. In this context we describe how an environment model can be created from real ultrasonic sensor data.

In this paper, we present the first sensor ever built using films grown by supersonic beam of cluster oxides as sensing material. Supersonic cluster beams, produced by a pulsed micro-plasma cluster source have successfully used to prepare nanocrystalline thin films of TiO/sub 2/. The sensors, prepared by using different deposition parameters, were suitable for use in a gas sensor array for electronic nose. Sensors showed a quite good response to ethanol, methanol and propanol. Principal component analysis was used as method for testing the array capability in discrimination and recognition of the volatile compounds.

Micro-electromechanical systems or MEMS are typically used for the measurement of physical phenomena associated with gun launched projectiles and other smart munitions. These devices generally experience not only the harsh environment encountered during initial shock and vibration at gun launch, but also the extremes of high temperature, high pressure and in some cases large electromagnetic fields associated with the launching mechanisms. This paper describes the various types of sensor requirements and characteristics for modern smart weapons, especially those of MEMS and in particular recent experimental results with silicon carbide MEMS pressure sensors.

In this paper, the frequency interference between two quartz crystal microbalances (QCMs) is investigated. Based on Mindlin's theory, the influence of design parameters on the frequency behavior of the QCM structure is studied.

Programmable mixed signal microcontrollers offer opportunities for the design of very low cost smart sensors.. A number of examples are shown which illustrate the performance and flexibility of the PSoC microcontroller in sensor applications.

Describes the current effort of creating cooperative analog/digital signal processing (CADSP) systems towards auditory sensor and signal processing applications. We address resolution issues that affect the choice of signal processing algorithms arriving from an analog sensor. We discuss current analog circuit approaches towards the front-end signal processing. We discuss our current IC approaches using this technology for noise suppression, as well as our current analog signal processing front-end system for speech recognition. Experimental data is presented from circuits fabricated using a 0.5 /spl mu/m n-well CMOS process available through MOSIS.