Physics
Sensors
Sensors are devices that detect and measure physical properties such as temperature, pressure, light, and motion. They convert these measurements into electrical signals that can be processed and analyzed. In physics, sensors play a crucial role in collecting data for experiments, monitoring environmental conditions, and controlling various systems.
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10 Key excerpts on "Sensors"
eBook - PDFArtificial Human Sensors
Science and Applications
- Peter Wide(Author)
- 2012(Publication Date)
- Jenny Stanford Publishing(Publisher)
Nevertheless, it is of importance to have enough knowledge of the sensor behaviours before considering the measure-ment specification – what do we want to achieve? This chapter is intended to be an initial insight to sensor technologies before moving on to the artificial perceptual sensor and its applications. There will be an overview of the classical sensor operational principles that extensively offer an introduction to the importance of artificial Sensors as an information source. A sensing unit can, in general terms, be defined as a; “device that is receptive to external stimuli and transforms it to communicable data ”. This definition is very broad and covers everything from human senses, for example the human eye, to gas Sensors used in a fire detection system and Sensors used to track the speed of a car. Artificial Human Sensors — Science and Applications by P. Wide Copyright c 2012 by Pan Stanford Publishing Pte Ltd www.panstanford.com 978-981-4241-58-8 76 Sensor Technologies However, to further restrict this definition to the principle of a sensor device, one definition can be found in Britannia, Merriam-Webster Dictionary on the word “sensor”; “a device that responds to a physical stimulus (as heat, light, sound, pressure, magnetism, or a particular motion) and transmits a resulting impulse (as for measurement or operating a control)”. This means that a sensor device can be described as an artificial device with physical properties. The sensor measures a specific local range of measurement interest, with indirect or direct operational principle and provides the foremost task of collecting specific information from that specific part of environment. However, to be correct in including all types of sensor principles, the refined version of the above definition may be as follows; “a device that responds to a physical, biological or chemical stimulus and transforms it to communicable data ”.
- Patrick F. Dunn(Author)
- 2011(Publication Date)
- CRC Press(Publisher)
2 Sensors in Engineering and Science CONTENTS 2.1 Chapter Overview ......................................................... 23 2.2 Physical Principles of Sensors ............................................. 23 2.3 Electric .................................................................... 24 2.3.1 Resistive ........................................................... 26 2.3.2 Capacitive ......................................................... 35 2.3.3 Inductive .......................................................... 39 2.4 Piezoelectric ............................................................... 41 2.5 Fluid Mechanic ............................................................ 45 2.6 Optic ...................................................................... 48 2.7 Photoelastic ............................................................... 63 2.8 Thermoelectric ............................................................ 65 2.9 Electrochemical ........................................................... 66 2.10 Problems .................................................................. 69 2.1 Chapter Overview Sensors can be understood best by examining the basic physical principles upon which they are designed. In this chapter, some Sensors involved in the measurement of length, relative displacement, force, pressure, acceleration, sound pressure, velocity, volumetric and mass flow rates, temperature, heat flux, relative humidity, circular frequency, particle diameter, void fraction, density, density gradient, gas concentration, and pH are presented. The fun-damental equations that relate what is sensed to its measurable output are given for each sensor described. 2.2 Physical Principles of Sensors The first step in choosing a sensor is to gain a thorough understanding of the basic physical principle behind its design and operation. The principles of Sensors [1] do not change. However, their designs change almost daily.
eBook - PDF- Owen Bishop(Author)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
11 Sensors and transducers Although the words 'sensor' and 'transducer' are often used as if they have the same meaning, their purpose is entirely different. A sensor is a device intended for detecting or measuring a physical quantity such as light, sound, pressure, temperature or magnetic field strength. It has an electrical output (often a varying potential or a current) which varies according to variations in the quantity it is detecting. A transducer is simply a device for converting one form of energy into another form of energy. Some Sensors are also transducers. For example, a crystal microphone (p. 107) converts the energy of sound waves into electrical potentials. It con-veniently converts the sound energy into a form that can be handled by an electronic circuit. But some other Sensors are not transducers. For example, a platinum resistance thermometer detects change in temperature as a change in the electrical resistance of its sensing element. Resistance is not a form of energy. Conversely, there are many transducers that are not Sensors; examples include electric lamps (convert electrical energy to light energy), electric motors (convert electrical energy to motion), cells (convert chemical energy to electri-cal energy). Descriptions of transducers begin on p. 115. Light Sensors and transducers are dealt with separately in Chapter 12. Temperature Sensors The resistance of metallic conductors increases with increasing temperature. If we measure the resistance of a length of wire, of known length, diameter and composition, we can determine its temperature. A platinum resistance thermo-meter consists of a coil of platinum wire wound on a ceramic former. One of its advantages is that it can be used over a very wide range of temperatures, from -100°C to several hundred degrees Celsius. Unfortunately, the resistance of platinum, like that of all metals is very low, so that a long wire is needed for the coil, which is bulky.
eBook - PDFSensors, Nanoscience, Biomedical Engineering, and Instruments
Sensors Nanoscience Biomedical Engineering
- Richard C. Dorf(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
Sensor: A device that produces a usable output in response to a specified measurand. Stability: The ability of a sensor to retain its characteristics over a relatively long period of time. References ANSI, ‘‘Electrical transducer nomenclature and terminology,’’ ANSI Standard MC6.1–1975 (ISA S37.1), Research Triangle Park, NC: Instrument Society of America, 1975. D.S. Ballentine, Jr. et al., Acoustic Wave Sensors: Theory, Design, and Physico-Chemical Applications , San Diego, CA: Academic Press, 1997. A.J. Bard and L.R. Faulkner, Electrochemical Methods: Fundamentals and Applications , New York: John Wiley & Sons, 1980. R.S.C. Cobbold, Transducers for Biomedical Measurements: Principles and Applications , New York: John Wiley & Sons, 1974. W.Go ¨pel, J. Hesse, and J.N. Zemel, ‘‘Sensors: a comprehensive survey,’’ in Fundamentals and General Aspects , vol. 1, T. Grandke and W.H. Ko, Eds., Weinheim, Germany: VCH, 1989. J. Janata, Principles of Chemical Sensors , New York: Plenum Press, 1989. M. Madou, Fundamentals of Microfabrication , Boca Raton, FL: CRC Press, 1997. Further Information Sensors: W. Gopel, J. Hesse, and J.N. Zemel, Eds., A Comprehensive Survey , Weinheim, Germany: VCH, 1989–1994. Vol. 1: Fundamentals and General Aspects, T. Grandke and W.H. Ko, Eds. Vol. 2, 3, pt. 1–2: Chemical and Biochemical Sensors, W. Gopel et al., Eds. Vol. 4: Thermal Sensors, T. Ricolfi and J. Scholz, Eds. Vol. 5: Magnetic Sensors, R. Boll and K.J. Overshott, Eds. Vol. 6: Optical Sensors, E. Wagner, R. Dandliker, and K. Spenner, Eds. Vol. 7: Mechanical Sensors, H.H. Bau, N.F. deRooij, and B. Kloeck, Eds. J. Carr, Sensors and Circuits: Sensors, Transducers, and Supporting Circuits for Electronic Instrumentation, Measurement , and Control, Englewood Cliffs, NJ: Prentice-Hall, 1993. J.R. Carstens, Electrical Sensors and Transducers, Englewood Cliffs, NJ: Regents/Prentice-Hall, 1993.
eBook - PDFAnalog and Digital Circuits for Electronic Control System Applications
Using the TI MSP430 Microcontroller
- Jerry Luecke(Author)
- 2004(Publication Date)
- Newnes(Publisher)
18 Introduction In Chapter 1 , Figure 1-8 shows the basic functions needed when going from an analog quantity to a digital output. The first of these is sensing the analog quantity. The device used in the function to sense the input quantity and convert it to an electrical signal is called a sensor —the main subject of this chapter. A sensor is a device that detects and converts a natural physical quantity into outputs that humans can interpret. Examples of outputs are meter readings, light outputs, linear motions and temperature variations. Chapter 1 indicated that a majority of these physical quantities are analog quantities; i.e., they vary smoothly and continuously. Sensors, in their simplest form, are devices that contain only a single element that does the necessary transformation. Although today, more and more complicated Sensors are being manufactured; they cover more than the basic function, containing sensing, signal conditioning and converting all in one package. In this chapter, in order to clearly communicate the sensing function, the majority of Sensors will be single element Sensors that output electrical signals—voltage, current or resistance. But also, closely coupled to Sensors with electrical outputs, Sensors are included that use magnetic fields for their operation. Temperature Sensors Oral Temperature Everyone, sometime or another, has had the need to find out their body tempera-ture or the body temperature of a member of their family. An oral thermometer like the one shown in Figure 3-1 was probably used. Liquid mercury inside of a glass tube expands and pushes up the scale on the tube as temperature increases. The scale is calibrated in degrees (ºF—Fahrenheit in this case) of body tempera-ture; therefore, the oral thermometer converts the physical quantity of temperature into a scale value that humans can read. The oral thermometer is a temperature sensor with a mechanical scale readout.
- Wolfgang Altmann(Author)
- 2005(Publication Date)
- Newnes(Publisher)
2 Process measurement and transducers 2.1 Objectives At the conclusion of this chapter, the student should: • Be able to explain the meaning of the terms accuracy, precision, sensitivity, resolution, repeatability, rangeability, span and hysteresis • Be able to make an appropriate selection of sensing devices for a particular process • Describe the Sensors used for measurement of temperature, pressure, flow and liquid level • List the methods of minimizing the interference effects of noise on our instrumentation system. 2.2 The definition of transducers and Sensors A transducer is a device that obtains information in the form of one or more physical quantities and converts this into an electrical output signal. Transducers consist of two principle parts, a primary measuring element referred to as a sensor, and a transmitter unit responsible for producing an electrical output that has some known relationship to the physical measurement as the basic components. In more sophisticated units, a third element may be introduced which is quite often microprocessor based. This is introduced between the sensor and the transmitter part of the unit and has amongst other things, the function of linearizing and ranging the transducer to the required operational parameters. 2.3 Listing of common measured variables In descending order of frequency of occurrence, the principal controlled variables in process control systems comprise: • Temperature • Pressure • Flow rate • Composition • Liquid level. Process measurement and transducers 19 Sections 2.4 through to 2.6 of this chapter list and describe these different types of transducers, ending with a methodology of selecting sensing devices. 2.4 The common characteristics of transducers All transducers, irrespective of their measurement requirements, exhibit the same characteristics such as range, span, etc. This section explains and demonstrates the interpretation of the most common of these characteristics.
eBook - PDFBioinspired Photonics
Optical Structures and Systems Inspired by Nature
- Viktoria Greanya(Author)
- 2015(Publication Date)
- CRC Press(Publisher)
265 7 S ENSORS 7.1 Introduction All creatures interact with the world in some manner. Our senses enable us to capture vast amounts of information to which we are constantly exposed. These complex, sophisticated systems help us take in information about our environment. Along with the signal process-ing units in our peripheral and central nervous system, we manage the data that drive our behavior, growth, and survival as individuals and as a species. Humans have significantly more than five senses. Beyond sight, taste, smell, pressure (touch), and sound, we have senses of time, pain, proprioception, temperature, hunger, and more. Animals have many variations on the senses we share, and some have sensing capabilities humans do not. Their senses operate at different wavelengths, different sensitivities, and via different structures with different transduction principles. Squid, spiders, and many insects can sense the polarization of light, as has been discussed earlier in Chapters 4 and 5. 1,2 Some birds, insects, and mammals are able to sense magnetic field directions via specific biological magnetorecep-tors, which are used for navigation. 3,4 In each organism, evolutionary pressure has driven our bodies to prioritize certain sensing modalities (certain types of information capture) over others. Sensors are our technological attempt to mimic senses and expand our ability to monitor and adjust to our environment. Man-made sen-sors have become critical and pervasive in modern human life with an ever-increasing number and variety, particularly in the last decades. We monitor our buildings and roadways for structural safety, we monitor our population for security, and we monitor ourselves for health and well-being. Sensors are everywhere from our gardens to our cars; our cell phones to our bodies; and the market for Sensors continues to grow. In the United States alone, sales of Sensors are in the tens of billions of dollars. 5 One of the fastest growing segments
eBook - PDF- Joseph D. Bronzino, Donald R. Peterson, Joseph D. Bronzino, Donald R. Peterson(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
In this chapter, we will attempt to review various examples of Sensors used for physical measurement in biological systems. Although it would be beyond the scope of this chapter to cover all of these in detail, the principal Sensors applied for biological measurement will be described. Each section will include a brief description of the principle of operation of the sensor and the underlying physical principles, examples of some of the more common forms of these Sensors for application in living systems, methods of signal processing for these Sensors where appropriate, and important considerations for when the sen-sor is applied. 2 Physical Sensors Michael R. Neuman Michigan Technological University 2.1 Introduction ...................................................................................... 2 -1 2.2 Description of Sensors ..................................................................... 2 -2 Linear and Angular Displacement Sensors • Velocity Measurement • Accelerometers • Force Measurement • Measurement of Fluid Dynamic Variables • Temperature Measurement 2.3 Biomedical Applications of Physical Sensors ............................. 2 -17 References .................................................................................................... 2 -19 Further Information ................................................................................... 2 -20 2 -2 Biomedical Sensors 2.2 Description of Sensors 2.2.1 Linear and Angular Displacement Sensors A comparison of various characteristics of displacement Sensors described in detail here is outlined in Table 2.2. 2.2.1.1 Variable Resistance Sensor One of the simplest Sensors for measuring linear or angular displacement is a variable resistor similar to the volume control on an audio electronic device [1].
eBook - PDFPractical Interfacing in the Laboratory
Using a PC for Instrumentation, Data Analysis and Control
- Stephen E. Derenzo(Author)
- 2003(Publication Date)
- Cambridge University Press(Publisher)
Laboratory Exercise 14 uses a silicon photodiode to measure light and the absorption of light by colored solutions. Laboratory Exercise 15 explores the thermoelectric heat pump and its ability to heat and cool a small system. Laboratory Exercise 16 measures the offset potential and frequency-dependent complex impedance for bare metal and Ag(AgCl) electrodes. Laboratory Exercise 17 measures the human electrocardiogram (ECG), phonocardiogram, and blood pressure. Laboratory Exercise 18 amplifies and processes the electromyogram (EMG) from the skin surface and relates it to the mechanical tension produced by the underlying muscles. Laboratory Exercise 19 measures the position of the eyes using the electrooculogram (EOG) to determine the maximum angular velocity of voluntary and involuntary eye motion. 226 227 4.1 Introduction Several important characteristics that are common to most Sensors are now de- scribed. 1. The transfer function (or response function) of a sensor is its output as a function of the quantity being sensed. It is usually expressed in terms of a curve or a formula. 2. The sensitivity of a sensor is defined as the change in output for a unit change in the quantity being sensed. This is the first derivative of the response curve and generally depends on the value of the quantity being measured. For example, the iron–constantan thermocouple has a sensitivity of 50 V ◦ C at 0 ◦ C. 3. The linearity error of a sensor is the difference between the sensor response and either a best-fit straight line or a straight line passing through the end points. In either case, the value of the linearity will depend on the range of measurements used. Generally, Sensors become more linear as the measurement range is restricted. For example, the thermocouple output depends almost linearly on temperature over a wide range.
eBook - ePubElectronic Portable Instruments
Design and Applications
- Halit Eren(Author)
- 2003(Publication Date)
- CRC Press(Publisher)
In microwave and Doppler radars, the Sensors contain Gunn diode oscillators (about 10-mW output) located in launching horns, and the receiving horns contain mixer diodes. The microwave beam, typically 10.7 GHz, is generated by the Gunn diode, and a low-frequency signal is generated when any object in the field of view moves. This signal is extracted suitably to work as a proximity detector of the moving object.2.16.2 Pressure Sensors
Pressure is defined as the normal force exerted on the unit surface area of an object. The SI unit of pressure is the Pascal (Pa), after Blaise Pascal (1623–1662), which is defined as newtons per square meter (Nm− 2 ). There are three types of pressure measurements that can be performed:- Absolute pressure—the pressure difference between the point of measurement and perfect vacuum where pressure is zero
- Gauge pressure—the pressure difference between the point of measurements and the ambient pressure
- Differential pressure—the pressure difference between two points
Some pressure Sensors involve large mechanical parts and permanent linkages that make them unsuitable for portable instruments. However, many electronic portable instruments are available, particularly for gas pressure measurements. The type of Sensors suitable for a particular application depends on characteristics of the object under investigation, such as gas, air, or liquid. Also, there are different types of Sensors for low-pressure, high-pressure, and differential pressure measurements.Most pressure Sensors operate on the principle of converting pressure to some form of physical displacement, such as compression of a spring or deformation of an object. If displacement is used, there are many options for converting displacement into electrical signals. However, because of the heavy reliance on the physical displacements, many pressure Sensors are sensitive to vibration and shock, which introduces a drawback to their use in portable instruments.Pressure can be sensed directly or indirectly. Indirect methods rely on the action of pressure to cause displacement of a diaphragm, a piston, or other device, so that the electronic sensing of displacement can be related to the pressure. The most commonly employed method is indirect pressure sensing. However, there are both direct and indirect pressure Sensors for atmospheric pressure sensing (about 101.3 kPa).
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