Sensors: Materials and Applications
Faculdade de Ciências e Tecnologia
Departamento de Ciências dos Materiais
Teacher in charge
Rodrigo Ferrão de Paiva Martins, Rui Alberto Garção Barreira do Nascimento Igreja
To make available a broad revision of concepts behind the design and fabrication of sensors and the materials envolved in sensor fabrication. It is an objective of this course to introduce the students to the sensoric technologies associated to the physical measurements.
There are no disciplines required prior to enrollment in this course. However it is assumed that student have general knowledge of mathematics, physics and chemistry.
1. Sensors and signals. Brief Introduction to Metrology. Physical principes of measurement and materials properties.
2. Temperature sensors - Resistance temperature sensors (RTDs). Methods for resistance measurements; poteniometer circuit; Wheatstone bridge. Sensibility and nonlinearity of the Wheatstone bridge (constant voltage and constant current). The thermistor. The problem of self-heating on temperature measurements. Thermocouples; properties and materials for thermocouple construction; measurement methods; cold junction compensation. Temperature measurements with semiconductors and integrated circuits. Radiant sensors; pyroelectric detectors; pyroelectric effect; methods and materials; pyrometers. Dynamic response of temperature sensors.
3. Strain and stress sensors - Resistance-type strain gages. Materials for strain gages. Etched-foil strain gages; instalation; the wheatstone bridge for strain gage signal conditioning; calibration methods; Effects of lead wires, switches and slip rings; electrical noise; temperature compensated strain gages; cross sensitivity factor; modulation and syncronos demodulation for strain gages signal conditioning. The stress gage. Methods for evaluation of principal stresses on a general state of stress using strain gages. Linear variable diferential transformer (LVDT).
4. Force, torque and pressure measurements - Load cells; link-type load cell; beam-type load cell; ring-type load cell. Torque measurements; torque cells. Pressure measurements; displacement-type ; diaphragm-type; piezoelectric-type.
5. Displacement, velocity, and accelaration measurements - Optical measurements methods; LVDT; Seismic transducers. Accelerometer; piezoelectric-type accelerometers; piezoelectric sensor circuits; charge amplifier for piezoelectric sensors. Measurement of transient signals.
6. Fluid flow measurements - insertion-type transducers; pitot tube; Hot-wire and hot-film anenometers (constant current and constant temperature). Drag-force velocity transducers. Venturi meters.
7. Chemical Sensors and multisensors systems - Transducers for chemical sensing; capacitive; cristal quartz microbalance; figaro type sensors. Sensitive layer materials. Adsorption and absortion of organic volatile molecules on sensitive layers. Methods for choosing polymer sensitive layers. Multisensor systems; methods for signal treatment on multisensor systems; methods for data reduction and data evaluation in multisensor systems (principal component analysis; linear discriminant analysis and neural networks).
Slides used in the course available through the MOODLE system
Instrumentation for Engeneering Measurements, James Dally, Wiley.
Les Capteurs en Instrumentation Industrielle, Georges Asch, Dunod.
Measurement Systems Applications and Design, Ernest O. Doebelin, McGraw-Hill.
Instrumentação Industrial, Gustavo da Silva, Escola Superior de Tecnologia de Setúbal.
AIP Handbook of Modern Sensors, Jacob Fraden, AIP Series in Modern Instrumentation.
The Measurement, Instrumentation and Sensors Handbook, ed John g Webster, IEEE Press.
Sensors Update - Wiley – VCH. Journals: Sensors and Actuators A and B, Elsevier. Sensors (IEEE).
Theoretical classes with datashow. Problem solving classes with student participation.
Practicals include theory preparation, experimental procedure and production of a small report.
Availability of the study material in the internet.
ADMISSION TO THE EXAM: Three reports of the labs sessions are produced which, after discussion of the work, are given a overall mark of NP. To be admitted to examination students must have a positive information in this component.
PASS: to be exempted of examination the student can attend two tests whose average must be equal or greater than 10 and none of them be less than 8.
The final classification is,
where NE is the average of the tests or the marks of the exam.