Modern Sensors Handbook E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 568

Veröffentlichungsjahr: 2013

Beschreibung

Modern sensors working on new principles and/or using new materials and technologies are more precise, faster, smaller, use less power and are cheaper. Given these advantages, it is vitally important for system developers, system integrators and decision makers to be familiar with the principles and properties of the new sensor types in order to make a qualified decision about which sensor type to use in which system and what behavior may be expected. This type of information is very difficult to acquire from existing sources, a situation this book aims to address by providing detailed coverage on this topic. In keeping with its practical theme, the discussion concentrates on sensor types used or having potential to be used in industrial applications.

Leseprobe

Table of Contents

Chapter 1. Pressure Sensors

1.1. Introduction

1.2. Pressure

1.3. Pressure ranges

1.4. Main physical principles

1.5. Calibration: pressure standards

1.6. Choosing a pressure sensor

1.7. References

1.8. Other pressure sensors manufacturers

1.9. Bibliography

Chapter 2. Optical Sensors

Introduction

2.1. Optical waveguides and fibers

2.2. Light sources and detectors

2.3. Sensors of position and movement

2.4. Optical sensors of dimensions

2.5. Optical sensors of pressure and force

2.6. Optical fiber sensors

2.7. Optical chemical sensors

2.8. Bibliography

Chapter 3. Flow Sensors

3.1. Introduction

3.2. Flow measurements based on the principle of difference in pressure

3.3. Flow measurements based on variable passage

3.4. Turbine flow meter

3.5. The mechanical flow meter (positive displacement)

3.6. Magnetic flow meter

3.7. The vortex flow meter

3.8. Ultrasonic flow meter

3.9. Coriolis mass-flow meters

3.10. Flow measurements for solid substances

3.11. Flow measurement for open channels with weirs

3.12. Choice and comparison of flow measurements

3.13. Bibliography

3.14. Website references

Chapter 4. Intelligent Sensors and Sensor Networks

4.1. Introduction

4.2. Intelligent sensors

4.3. Sensor networks and interfaces

Chapter 5. Accelerometers and Inclinometers

5.1. Introduction

5.2. Acceleration

5.3. Application ranges

5.4. Main models of accelerometers

5.5. The signal processing associated with accelerometers

5.6. Manufacturing process

5.7. The calibrations:

5.8. Examples of accelerometers and inclinometers

5.9. List of Manufacturers of Accelerometers

5.10. References

5.11. Bibliography

Chapter 6. Chemical Sensors and Biosensors

6.1. Introduction

6.2. What is involved in developing a sensor?

6.3. Electrochemical sensors

6.4. Optical sensors

6.5. Acoustic (mass) sensors

6.6. Biosensors

6.7. Future trends

6.8. Conclusions

6.9. References

Chapter 7. Level, Position and Distance

7.1. Introduction

7.2. Resistive LPD sensors

7.3. Inductive LPD sensors

7.4. Magnetic LPD sensors

7.5. Capacitive LPD sensors

7.6. Optical LPD sensors

7.7. Ultrasonic sensors

7.8. Microwave distance sensors (radar)

7.9. Level measurement

7.10. Conclusions and trends

7.11. References

7.12. Online references

Chapter 8. Temperature Sensors

8.1. Introduction

8.2. Thermal measuring techniques

8.3. Physical or direct temperature measurement

8.4. Thermoelectric measurements (thermocouples)

8.5. Resistance temperature detectors (RTDs)

8.6. Thermistors

8.7. Monolithic temperature sensors (IC sensor)

8.8. Pyrometers

8.9. References

8.10. Bibliography

Chapter 9. Solid State Gyroscopes and Navigation

9.1. Introduction

9.2. The angular rate

9.3. Different ranges of rate gyro

9.4. Main models of rate gyro

9.5. Calibration of rate sensors

9.6. General features of the gyrometers

9.7. The main manufacturers

9.8. References

9.9. Bibliography

Chapter 10. Magnetic Sensors

10.1. Introduction

10.2. Hall sensors

10.3. AMR sensors

10.4. GMR sensors

10.5. Induction and fluxgate sensors

10.6. Other magnetic field sensors

10.7. Magnetic position sensors

10.8. Contactless current sensors

10.9. References

Chapter 11. New Technologies and Materials

11.1. Introduction: MEMS

11.2. Materials

11.3. Silicon planar IC technology

11.4. Deposition technologies

11.5. Etching processes

11.6. 3-D microfabrication techniques

11.7. References

List of Authors

Index

First published in Great Britain and the United States in 2007 by ISTE Ltd

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

ISTE Ltd6 Fitzroy SquareLondon W1T 5DXUKwww.iste.co.ukISTE USA 4308 Patrice RoadNewport Beach, CA 92663USA

© ISTE Ltd, 2007

The rights of Pavel Ripka and Alois Tipek to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Cataloging-in-Publication Data

Modern sensors handbook/edited by Pavel Ripka, Alois Tipek.

p. cm.

ISBN 978-1-905209-66-8

1. Detectors--Handbooks, manuals, etc. I. Ripka, Pavel. II. Tipek, Alois.

TA165.M585 2007

681'.2--dc22

2007003344

British Library Cataloguing-in-Publication Data

A CIP record for this book is available from the British Library

ISBN 13: 978-1-905209-66-8

Chapter 1

Pressure Sensors1

1.1. Introduction

Together with temperature, pressure is one of the most important physical quantities in our environment. Pressure is a significant parameter in such varied disciplines as thermodynamics, aerodynamics, acoustics, fluid mechanics, soil mechanics and biophysics. As an example of important industrial applications of pressure measurement we may consider power engineering. Hydroelectric, thermal, nuclear, wind and other plants generating mechanical, thermal or electrical energy require the constant monitoring and control of pressures: overpressure could cause the deterioration of enclosures or drains and cause very significant damage.

As a significant parameter, pressure enters into the control and operation of manufacturing units that are automated or operated by human operators. Pressure measurement is also used in robotics, either directly in controls or indirectly as a substitute for touch (artificial skin for example), for pattern recognition or for determining strength of grip. All these activities require instrument chains in which the first element is the pressure sensor, delivering data relating to the pressure of compressed air, gas, vapor, oil or other fluids, determining the correct operation of machines or systems.

The variety of mentioned applications demands a great diversity of sensors. This diversity also derives from the fact that pressure covers a very wide range from ultra-high vacuums to ultra-high pressures. It can be expressed as an absolute value (compared to vacuum) or as a relative value (compared to atmospheric pressure); it can also represent a difference between two pressures or relate to various media and fluids whose physical characteristics (e.g. temperature) or chemical characteristics (e.g. risk of corrosion) are very varied. Pressure units are summarized in Table 1.1.

1.2. Pressure

In what follows, we will consider the different physical characteristics necessary to understand pressure sensors: pressure as a physical quantity, and various sensor models with absolute, relative or differential pressure sensors. We will take a brief look at the physical properties of fluids.

1.2.1. Pressure as a physical quantity

1.2.1.1. Static pressure

From a phenomenological point of view, pressure, p, as a macroscopic parameter is defined starting with element of force , exerted perpendicularly on an element of surface of the wall, by the fluid contained in the container:

(1.1) 

The element of force caused by pressure p is perpendicular to the element of surface .

For pressure p inside the fluid with free surface we may write:

(1.2) 

p0: atmospheric pressure

ρgh: hydrostatic pressure

ρ: density

g: acceleration of gravity at the place of measurement

h: distance from the free surface

1.2.1.2. Units

Table 1.1.Units of pressure

1.2.2. Absolute, relative and differential sensors

An absolute pressure sensor measures static, dynamic or total pressure with reference to a vacuum (see Figure 1.1).

Figure 1.1.Absolute pressure sensor

A relative pressure sensor measures static, dynamic or total pressure with reference to ambient atmospheric pressure (Figure 1.2).

Figure 1.2.Relative pressure sensor

A sealed relative pressure sensor measures static, dynamic or total pressure with reference to ambient atmospheric pressure, sealed at the time of manufacture of the sensor (see Figure 1.3).

Figure 1.3.Sealed Relative pressure sensor

A differential pressure sensor measures a static, dynamic or total pressure with reference to an unspecified variable pressure p2 (Figure 1.4).

Figure 1.4.Differential pressure sensor

1.2.3. Fluid physical properties

In static fluids, the pressure force F is exerted on the surface originates only from the random kinetic energy of molecules. In dynamic fluids force F originates from the random and directed kinetic energy of the molecules.

We generally distinguish between two main fluid families: gases and liquids.

1.2.3.1. Liquids

The total pressure is the sum of the static pressure, the pressure due to external forces and the dynamic pressure. This has the same value in all points for a fluid moving horizontally (incompressible, negligible viscosity, like liquids), following Bernoulli’s theorem:

(1.3) 

with:

pt: total pressure

ps: static pressure

pd: dynamic pressure

v: local velocity

ρ: density

1.2.3.2. Gases

The pressure of a gas in a tank is the force exerted by gas on the walls of the tank per unit of area. When a tank contains a mixture of gases, we can define a partial pressure for each of them. The sum of the partial pressures is equal to the total pressure. The equation of an ideal gas is:

(1.4) 

p: pressure

n: number of molecules

T: temperature

V: volume

kB: Boltzmann constant

According to the kinetic theory, the molecules of a gas are driven in a continual and random manner and bump into each other. The trajectory of a molecule between two shocks is a right-hand side segment traversed at constant speed and the direction of a segment after a shock has no correlation with the direction of the segment before the shock. The trajectory of a molecule is therefore a broken line, the average value l of the length of its segments being the free mean course.

When the gas is contained in an enclosure, the molecules also have collisions with the walls and the pressure that they exert on them results from the average effect of these collisions.