Self-calibrating closed-loop circuit for configurable constant voltage thermal anemometers

A new circuit is described which applies a configurable voltage across an RTD while the current flowing through it is measured with a current mirror. The circuit also allows working with voltages above the IC supply voltage to cope with the high power RTD dissipation normally required in thermal anemometers. The circuit is periodically calibrated to cancel the errors and amplifier offset and therefore improves measurement accuracy. Experimental measurements of the circuit fabricated using 0.35 mu m AMS technology show the functionality and improved power efficiency.Postprint (published version

CMOS-Integrated Single-Element Thermal Flow Sensors

Flow rate sensors for in situ gas or liquid monitoring typically comprise multiple transducer elements, including a heater and one or more temperature sensors to measure the rate of heat energy removal by the flowing fluid. The need for multiple transducer elements limits feasibility of shrinking these sensors to microfluidic flow channels and their integration into standard CMOS processes. In this work, a thermal flow sensor architecture is presented, which is integrated into a CMOS IC without additional post-processing. The architecture uses a single, resistive transducer element to measure fluid flow with a two-phase control and measurement algorithm. Experimental results demonstrate feasibility of the flow sensor architecture using a discrete micron-scale resistor structure, and using an integrated resistor structure for measuring air flow. By separating heating and temperature measurement in time, instead of in space, this method significantly decreases required transducer area and allows for the architecture to be scaled down to an integrated CMOS thermal flow sensor

Scanning Thermal Microscopy Methodology for Accurate and Reliable Thermal Measurement

Ph.DDOCTOR OF PHILOSOPH

Survey of environmental parameter sensors for a personal heat stress monitor

"This report summarizes the results of a directed survey and review of environmental parameter sensors for use in a personal heat stress monitor unit. A discussion of sensing techniques is given with descriptive details on the sensor's physical characteristics, theoretical basis of sensor operation, and suitability for use in a personal monitor unit. The parameters of interest in this survey are air velocity, dry bulb temperature, wet bulb temperature, natural wet bulb temperature and 1-inch globe temperature or mean radiant temperature. The sensors and measurement techniques found to be useable or adaptable through modification for use in a heat stress monitor are identified and a preliminary design is given which will permit the construction and testing of a complete system. With reference to the 6-inch globe temperature, two options are given with each requiring additional development effort for implementation. The objective of this survey did not include data recording methods or data processing. However, a short discussion is included discussing current techniques which are applicable to the system requirements." - NIOSHTIC-2NIOSHTIC no. 2004657976-182.pdf?id=10.26616/NIOSHPUB761821976Contract No. 210-75-00361117

DESIGN OF SMART SENSORS FOR DETECTION OF PHYSICAL QUANTITIES

Microsystems and integrated smart sensors represent a flourishing business thanks to the manifold benefits of these devices with respect to their respective macroscopic counterparts. Miniaturization to micrometric scale is a turning point to obtain high sensitive and reliable devices with enhanced spatial and temporal resolution. Power consumption compatible with battery operated systems, and reduced cost per device are also pivotal for their success. All these characteristics make investigation on this filed very active nowadays. This thesis work is focused on two main themes: (i) design and development of a single chip smart flow-meter; (ii) design and development of readout interfaces for capacitive micro-electro-mechanical-systems (MEMS) based on capacitance to pulse width modulation conversion. High sensitivity integrated smart sensors for detecting very small flow rates of both gases and liquids aiming to fulfil emerging demands for this kind of devices in the industrial to environmental and medical applications. On the other hand, the prototyping of such sensor is a multidisciplinary activity involving the study of thermal and fluid dynamic phenomenon that have to be considered to obtain a correct design. Design, assisted by finite elements CAD tools, and fabrication of the sensing structures using features of a standard CMOS process is discussed in the first chapter. The packaging of fluidic sensors issue is also illustrated as it has a great importance on the overall sensor performances. The package is charged to allow optimal interaction between fluids and the sensors and protecting the latter from the external environment. As miniaturized structures allows a great spatial resolution, it is extremely challenging to fabricate low cost packages for multiple flow rate measurements on the same chip. As a final point, a compact anemometer prototype, usable for wireless sensor network nodes, is described. The design of the full custom circuitry for signal extraction and conditioning is coped in the second chapter, where insights into the design methods are given for analog basic building blocks such as amplifiers, transconductors, filters, multipliers, current drivers. A big effort has been put to find reusable design guidelines and trade-offs applicable to different design cases. This kind of rational design enabled the implementation of complex and flexible functionalities making the interface circuits able to interact both with on chip sensors and external sensors. In the third chapter, the chip floor-plan designed in the STMicroelectronics BCD6s process of the entire smart flow sensor formed by the sensing structures and the readout electronics is presented. Some preliminary tests are also covered here. Finally design and implementation of very low power interfaces for typical MEMS capacitive sensors (accelerometers, gyroscopes, pressure sensors, angular displacement and chemical species sensors) is discussed. Very original circuital topologies, based on chopper modulation technique, will be illustrated. A prototype, designed within a joint research activity is presented. Measured performances spurred the investigation of new techniques to enhance precision and accuracy capabilities of the interface. A brief introduction to the design of active pixel sensors interface for hybrid CMOS imagers is sketched in the appendix as a preliminary study done during an internship in the CNM-IMB institute of Barcelona

Integral sensor telemetry, phase a report

Application of integral sensor transmitters to factory stage checkout of Saturn type vehicl

MEMS Accelerometers

Micro-electro-mechanical system (MEMS) devices are widely used for inertia, pressure, and ultrasound sensing applications. Research on integrated MEMS technology has undergone extensive development driven by the requirements of a compact footprint, low cost, and increased functionality. Accelerometers are among the most widely used sensors implemented in MEMS technology. MEMS accelerometers are showing a growing presence in almost all industries ranging from automotive to medical. A traditional MEMS accelerometer employs a proof mass suspended to springs, which displaces in response to an external acceleration. A single proof mass can be used for one- or multi-axis sensing. A variety of transduction mechanisms have been used to detect the displacement. They include capacitive, piezoelectric, thermal, tunneling, and optical mechanisms. Capacitive accelerometers are widely used due to their DC measurement interface, thermal stability, reliability, and low cost. However, they are sensitive to electromagnetic field interferences and have poor performance for high-end applications (e.g., precise attitude control for the satellite). Over the past three decades, steady progress has been made in the area of optical accelerometers for high-performance and high-sensitivity applications but several challenges are still to be tackled by researchers and engineers to fully realize opto-mechanical accelerometers, such as chip-scale integration, scaling, low bandwidth, etc

Data Acquisition Applications

Data acquisition systems have numerous applications. This book has a total of 13 chapters and is divided into three sections: Industrial applications, Medical applications and Scientific experiments. The chapters are written by experts from around the world, while the targeted audience for this book includes professionals who are designers or researchers in the field of data acquisition systems. Faculty members and graduate students could also benefit from the book

Bolometers

Infrared Detectors and technologies are very important for a wide range of applications, not only for Military but also for various civilian applications. Comparatively fast bolometers can provide large quantities of low cost devices opening up a new era in infrared technologies. This book deals with various aspects of bolometer developments. It covers bolometer material aspects, different types of bolometers, performance limitations, applications and future trends. The chapters in this book will be useful for senior researchers as well as beginning graduate students