Three sentences:
Sound waves are mechanical waves that propagate through a medium as variations in pressure. Acoustic sensors convert these pressure variations into electrical signals using various transduction mechanisms like piezoelectricity, capacitance changes, or fiber optic interferometry. Common acoustic sensors include microphones, hydrophones, and surface acoustic wave sensors which propagate mechanical waves along the surface of piezoelectric materials to enable highly sensitive measurement.
Surface acoustic wave sensors rely on modulating and transducing surface acoustic waves to sense physical phenomena. They have advantages including compact size, high sensitivity, fast response, and ability to operate wirelessly in harsh environments. A basic SAW sensor consists of a piezoelectric substrate with input and output interdigital transducers to launch and receive surface acoustic waves. The transducers convert between electrical and mechanical surface waves, allowing remote sensing by analyzing signal changes induced by external factors interacting with the waves.
How can variables be measured in environments that are too hot, too cold, or moving too fast for traditional circuit-based sensors? A new technology for obtaining multiple, real-time measurements under extreme environmental conditions is being developed under Phase 1 and 2 funding contracts from NASA's Kennedy Space Center’s Small Business Technology Transfer (STTR) program. Opportunities for early deployment licensing and Phase 3 STTR contracts are now being accepted.
Passive, remote measuring systems can be created using new Orthogonal Frequency Code (OFC) multiplexing techniques and specially developed, next-generation SAW sensors. As a result, very cost-effective applications such as spaceflight sensing (for instance, temperature, pressure, or acceleration monitoring), remote cryogenic fluid level sensing, or an almost limitless number of other rigorous monitoring applications are possible.
Proximity sensors detect objects without physical contact using various technologies like inductive, capacitive, ultrasonic and optical. Inductive sensors detect metallic objects using a coil and oscillator to create a magnetic field. Capacitive sensors detect metallic and nonmetallic objects by measuring capacitance changes between the sensor and object. Ultrasonic sensors use sound waves above human hearing range, while optical sensors use light beams reflected off objects. Key features of good sensors include precision, accuracy, response speed, operating range, reliability, easy calibration and low cost.
A sensor is a device that detects and responds to some type of input from the physical environment.
The specific input could be light, heat, motion, moisture, pressure, or any one of a great number of other environmental phenomena.
The output is generally a signal that is converted to human-readable display at the sensor location or transmitted electronically over a network for reading or further processing.
Micro machining involves removing material at the micro/nano scale to create small features and high precision surfaces. Key techniques include photolithography, which uses light passing through masks to pattern photoresist, and various etching methods like wet, dry, and plasma etching to remove material. Other important microfabrication processes are bulk micromachining, which etches the silicon substrate, surface micromachining which builds structures in layers, and LIGA which uses X-rays to create high aspect ratio metal parts through electroplating. These micro machining techniques enable manufacturing of complex micro-scale parts for applications like MEMS devices and biomedical tools.
Static and dynamic characteristics of instrumentsfreddyuae
Static characteristics describe an instrument's performance when measuring quantities that remain constant or vary slowly. They include properties like linearity, sensitivity, resolution, repeatability, hysteresis, and environmental effects. Dynamic characteristics describe how the instrument responds when the measured quantity varies rapidly over time. Instruments can be modeled as a series of blocks, each with their own static and dynamic transfer functions. The overall static and dynamic responses are obtained by multiplying the individual block transfer functions. Characterizing both the static and dynamic behavior is important for understanding an instrument's performance.
The document discusses different types of sensors including resistive, capacitive, piezoelectric, magnetic, and strain gauge sensors. It provides details on resistive sensors and their major types like potentiometers, strain gauges, thermistors, and light dependent resistors. The document also describes capacitive sensors, piezoelectric transducers, magnetic sensors like Hall effect sensors, and variable reluctance sensors. Finally, it covers strain gauge sensors, their working, and applications.
Surface acoustic wave sensors rely on modulating and transducing surface acoustic waves to sense physical phenomena. They have advantages including compact size, high sensitivity, fast response, and ability to operate wirelessly in harsh environments. A basic SAW sensor consists of a piezoelectric substrate with input and output interdigital transducers to launch and receive surface acoustic waves. The transducers convert between electrical and mechanical surface waves, allowing remote sensing by analyzing signal changes induced by external factors interacting with the waves.
How can variables be measured in environments that are too hot, too cold, or moving too fast for traditional circuit-based sensors? A new technology for obtaining multiple, real-time measurements under extreme environmental conditions is being developed under Phase 1 and 2 funding contracts from NASA's Kennedy Space Center’s Small Business Technology Transfer (STTR) program. Opportunities for early deployment licensing and Phase 3 STTR contracts are now being accepted.
Passive, remote measuring systems can be created using new Orthogonal Frequency Code (OFC) multiplexing techniques and specially developed, next-generation SAW sensors. As a result, very cost-effective applications such as spaceflight sensing (for instance, temperature, pressure, or acceleration monitoring), remote cryogenic fluid level sensing, or an almost limitless number of other rigorous monitoring applications are possible.
Proximity sensors detect objects without physical contact using various technologies like inductive, capacitive, ultrasonic and optical. Inductive sensors detect metallic objects using a coil and oscillator to create a magnetic field. Capacitive sensors detect metallic and nonmetallic objects by measuring capacitance changes between the sensor and object. Ultrasonic sensors use sound waves above human hearing range, while optical sensors use light beams reflected off objects. Key features of good sensors include precision, accuracy, response speed, operating range, reliability, easy calibration and low cost.
A sensor is a device that detects and responds to some type of input from the physical environment.
The specific input could be light, heat, motion, moisture, pressure, or any one of a great number of other environmental phenomena.
The output is generally a signal that is converted to human-readable display at the sensor location or transmitted electronically over a network for reading or further processing.
Micro machining involves removing material at the micro/nano scale to create small features and high precision surfaces. Key techniques include photolithography, which uses light passing through masks to pattern photoresist, and various etching methods like wet, dry, and plasma etching to remove material. Other important microfabrication processes are bulk micromachining, which etches the silicon substrate, surface micromachining which builds structures in layers, and LIGA which uses X-rays to create high aspect ratio metal parts through electroplating. These micro machining techniques enable manufacturing of complex micro-scale parts for applications like MEMS devices and biomedical tools.
Static and dynamic characteristics of instrumentsfreddyuae
Static characteristics describe an instrument's performance when measuring quantities that remain constant or vary slowly. They include properties like linearity, sensitivity, resolution, repeatability, hysteresis, and environmental effects. Dynamic characteristics describe how the instrument responds when the measured quantity varies rapidly over time. Instruments can be modeled as a series of blocks, each with their own static and dynamic transfer functions. The overall static and dynamic responses are obtained by multiplying the individual block transfer functions. Characterizing both the static and dynamic behavior is important for understanding an instrument's performance.
The document discusses different types of sensors including resistive, capacitive, piezoelectric, magnetic, and strain gauge sensors. It provides details on resistive sensors and their major types like potentiometers, strain gauges, thermistors, and light dependent resistors. The document also describes capacitive sensors, piezoelectric transducers, magnetic sensors like Hall effect sensors, and variable reluctance sensors. Finally, it covers strain gauge sensors, their working, and applications.
A piezoelectric sensor uses the piezoelectric effect to convert changes in pressure, acceleration, temperature, strain or force into an electrical charge. Piezoelectric sensors are versatile tools that are used for quality assurance, process control, and research and development across many industries. They have limitations for static measurements but are otherwise a mature and reliable sensing technology. Piezoresistive sensors undergo a change in electrical resistance when subjected to mechanical strain, and are commonly used in integrated circuits made from piezoresistive materials like silicon.
In this slide there is all about the digital transducer and its types.Its is very helpful in making short notes of transducer. There is a simple description.
Piezoelectric and piezoresistive sensors convert mechanical energy into electrical signals. Piezoelectric materials generate a voltage when pressure is applied due to internal crystal structure changes. Common piezoelectric materials include quartz and ceramics like lead zirconate titanate. Piezoresistive sensors use semiconductors whose resistance changes with applied pressure. Strain gauges also measure stress by detecting resistance changes in foil patterns attached to surfaces. Both sensor types are used in applications like accelerometers, pressure sensors, and medical devices due to their high sensitivity and small size.
This slide contains information about two type of accelerometer :- 1. Seismic Accelerometer 2 :- Displacement type accelerometer.
it contains working and construction.
MR3491 SENSORS AND INSTRUMENTATION (UNIT III - FORCE, MAGNETIC AND HEADING SE...A R SIVANESH M.E., (Ph.D)
MR3491 SENSORS AND INSTRUMENTATION
UNIT III - FORCE, MAGNETIC AND HEADING SENSORS
Strain Gage, Load Cell, Magnetic Sensors –types, principle, requirement and advantages: Magneto resistive – Hall Effect – Current sensor Heading Sensors – Compass, Gyroscope, Inclinometers
This document discusses different types of sensors and their characteristics. It covers the differences between active and passive instruments, as well as null-type and deflection-type instruments. It also discusses analogue versus digital instruments and some key sensor performance characteristics such as accuracy, precision, threshold, resolution, sensitivity, linearity, hysteresis and more. Key factors that influence sensor selection are resolution requirements, cost, accuracy needs, and application environment. Proper sensor selection depends on balancing these factors for each unique measurement scenario.
Sensors are devices that measure physical quantities and convert them into signals that can be read by observers or instruments. The document discusses several common sensors: infrared (IR) sensors, sound sensors, temperature sensors, and discusses their working principles and applications. It also provides details on using timers and integrated circuits like the 555 timer IC to process sensor output signals.
Microelectromechanical Systems (MEMS) are miniature devices comprising of integrated mechanical (levers, springs, deformable membranes, vibrating structures, etc.) and electrical (resistors, capacitors, inductors, etc.) components designed to work in concert to sense and report on the physical properties of their immediate or local environment, or, when signaled to do so, to perform some kind of controlled physical interaction or actuation with their immediate or local environment
The document describes the LIGA process for fabricating microdevices. It involves three main steps: (1) X-ray lithography to pattern thick photoresist layers, (2) electroplating of metal into the pattern, and (3) removal of the photoresist template to produce free-standing metal microstructures. Key aspects of the LIGA process include using synchrotron radiation for X-ray exposure due to its high intensity and tunability, as well as the ability to create high-aspect-ratio microstructures through thick-resist exposure and development.
This document discusses different types of proximity sensors, including inductive, capacitive, ultrasonic, and optical proximity sensors. It provides details on the working principles, components, advantages, and applications of each sensor type. Inductive proximity sensors detect metallic objects using a coil and oscillator. Capacitive sensors detect both metallic and non-metallic objects by measuring capacitance changes. Ultrasonic sensors use ultrasonic sound waves to detect objects, while optical sensors use infrared or visible light and can operate in a through-beam or reflective configuration. The document concludes by noting common applications of proximity sensors in machinery, automotive, and other industrial sectors.
This presentation provides an overview of optical sensors, including their introduction, working principles, classification, applications, and future trends. Optical sensors are classified as either extrinsic or intrinsic based on whether the light interacts with the measurand inside or outside of the optical fiber. They have a wide range of applications in areas such as temperature, chemical concentration, strain, biomedical, and more. The presentation concludes that optical sensor technology will continue to improve and be an important area of research going forward.
Vibration sensors detect vibrations and convert them into electrical signals. There are two main types: contact sensors that must mount directly to the object, and non-contact sensors that measure vibrations without direct contact. Common contact sensors include piezoelectric accelerometers, piezoresistive accelerometers, and strain gauges. Common non-contact sensors include microphones, laser displacement sensors, and eddy current sensors. Vibration data can be analyzed in both the time and frequency domains to diagnose machine problems.
This document provides an overview of transducers. It defines a transducer as a device that converts a non-electrical physical quantity into an electrical signal. Transducers contain a sensing element that produces a measurable response to physical changes and a transduction element that converts the sensor output into an electrical form. Transducers are classified based on their output signal type (analog or digital), application method (primary or secondary), energy conversion method (active or passive), and transduction principle used (resistive, capacitive, inductive, etc.). Examples of common transducers discussed include thermocouples, strain gauges, thermistors, and linear variable differential transformers. Selection factors and applications of transducers
This document discusses various types of mechanical sensors and their applications. It describes sensors that measure mechanical phenomena like pressure, force, torque, inertia, and flow. Pressure sensors are used in applications like manometers, barometers, microphones, and automotive parts. Force and torque sensors can be used in control systems, testing equipment, and for measuring power transmission. Inertial sensors like accelerometers have applications in industry, military, vibration monitoring, and safety systems. Flow sensors measure flow rates using principles of heat transfer and are used in microsensors and velocimetry applications. The document provides details on common sensing techniques like piezoresistivity, piezoelectricity, capacitive, inductive and resonant techniques.
Load cells are transducers that convert an applied force into an electrical signal. There are several types of load cells including resistive, capacitive, vibrating wire, piezoelectric, hydraulic, and pneumatic. Resistive load cells use strain gauges to measure deformation from applied forces. Capacitive load cells measure deformation capacitively. Vibrating wire load cells monitor loads in structural elements. Piezoelectric load cells generate voltage when force is applied to piezoelectric materials. Hydraulic load cells use fluid pressure from piston movement to measure force. Pneumatic load cells balance applied force with counteracting air pressure.
Longitudinal waves are waves where the medium oscillates in the direction of wave propagation. Sound is a longitudinal wave that travels through air by alternately compressing and rarefying the air. The speed of sound depends on the density and bulk modulus of the medium. Acoustic sensors like microphones convert pressure variations from sound waves into electrical signals. Common types include piezoelectric, capacitive, and resistive microphones. Surface acoustic wave sensors use interdigitated transducers on a piezoelectric substrate to generate and detect surface waves for sensing applications like pressure, strain, and temperature.
Ultrasound is produced by piezoelectric crystals in transducers that convert electrical pulses into sound waves and received echoes into electrical signals. Transducers operate in shock, burst, or continuous excitation modes. The piezoelectric crystals resonate at specific frequencies determined by their thickness and composition. Damping materials in transducers shorten pulse duration to improve image resolution by reducing echo overlap. Transducers use the pulse-echo principle to transmit sound pulses into the body and receive returning echoes to create ultrasound images.
A piezoelectric sensor uses the piezoelectric effect to convert changes in pressure, acceleration, temperature, strain or force into an electrical charge. Piezoelectric sensors are versatile tools that are used for quality assurance, process control, and research and development across many industries. They have limitations for static measurements but are otherwise a mature and reliable sensing technology. Piezoresistive sensors undergo a change in electrical resistance when subjected to mechanical strain, and are commonly used in integrated circuits made from piezoresistive materials like silicon.
In this slide there is all about the digital transducer and its types.Its is very helpful in making short notes of transducer. There is a simple description.
Piezoelectric and piezoresistive sensors convert mechanical energy into electrical signals. Piezoelectric materials generate a voltage when pressure is applied due to internal crystal structure changes. Common piezoelectric materials include quartz and ceramics like lead zirconate titanate. Piezoresistive sensors use semiconductors whose resistance changes with applied pressure. Strain gauges also measure stress by detecting resistance changes in foil patterns attached to surfaces. Both sensor types are used in applications like accelerometers, pressure sensors, and medical devices due to their high sensitivity and small size.
This slide contains information about two type of accelerometer :- 1. Seismic Accelerometer 2 :- Displacement type accelerometer.
it contains working and construction.
MR3491 SENSORS AND INSTRUMENTATION (UNIT III - FORCE, MAGNETIC AND HEADING SE...A R SIVANESH M.E., (Ph.D)
MR3491 SENSORS AND INSTRUMENTATION
UNIT III - FORCE, MAGNETIC AND HEADING SENSORS
Strain Gage, Load Cell, Magnetic Sensors –types, principle, requirement and advantages: Magneto resistive – Hall Effect – Current sensor Heading Sensors – Compass, Gyroscope, Inclinometers
This document discusses different types of sensors and their characteristics. It covers the differences between active and passive instruments, as well as null-type and deflection-type instruments. It also discusses analogue versus digital instruments and some key sensor performance characteristics such as accuracy, precision, threshold, resolution, sensitivity, linearity, hysteresis and more. Key factors that influence sensor selection are resolution requirements, cost, accuracy needs, and application environment. Proper sensor selection depends on balancing these factors for each unique measurement scenario.
Sensors are devices that measure physical quantities and convert them into signals that can be read by observers or instruments. The document discusses several common sensors: infrared (IR) sensors, sound sensors, temperature sensors, and discusses their working principles and applications. It also provides details on using timers and integrated circuits like the 555 timer IC to process sensor output signals.
Microelectromechanical Systems (MEMS) are miniature devices comprising of integrated mechanical (levers, springs, deformable membranes, vibrating structures, etc.) and electrical (resistors, capacitors, inductors, etc.) components designed to work in concert to sense and report on the physical properties of their immediate or local environment, or, when signaled to do so, to perform some kind of controlled physical interaction or actuation with their immediate or local environment
The document describes the LIGA process for fabricating microdevices. It involves three main steps: (1) X-ray lithography to pattern thick photoresist layers, (2) electroplating of metal into the pattern, and (3) removal of the photoresist template to produce free-standing metal microstructures. Key aspects of the LIGA process include using synchrotron radiation for X-ray exposure due to its high intensity and tunability, as well as the ability to create high-aspect-ratio microstructures through thick-resist exposure and development.
This document discusses different types of proximity sensors, including inductive, capacitive, ultrasonic, and optical proximity sensors. It provides details on the working principles, components, advantages, and applications of each sensor type. Inductive proximity sensors detect metallic objects using a coil and oscillator. Capacitive sensors detect both metallic and non-metallic objects by measuring capacitance changes. Ultrasonic sensors use ultrasonic sound waves to detect objects, while optical sensors use infrared or visible light and can operate in a through-beam or reflective configuration. The document concludes by noting common applications of proximity sensors in machinery, automotive, and other industrial sectors.
This presentation provides an overview of optical sensors, including their introduction, working principles, classification, applications, and future trends. Optical sensors are classified as either extrinsic or intrinsic based on whether the light interacts with the measurand inside or outside of the optical fiber. They have a wide range of applications in areas such as temperature, chemical concentration, strain, biomedical, and more. The presentation concludes that optical sensor technology will continue to improve and be an important area of research going forward.
Vibration sensors detect vibrations and convert them into electrical signals. There are two main types: contact sensors that must mount directly to the object, and non-contact sensors that measure vibrations without direct contact. Common contact sensors include piezoelectric accelerometers, piezoresistive accelerometers, and strain gauges. Common non-contact sensors include microphones, laser displacement sensors, and eddy current sensors. Vibration data can be analyzed in both the time and frequency domains to diagnose machine problems.
This document provides an overview of transducers. It defines a transducer as a device that converts a non-electrical physical quantity into an electrical signal. Transducers contain a sensing element that produces a measurable response to physical changes and a transduction element that converts the sensor output into an electrical form. Transducers are classified based on their output signal type (analog or digital), application method (primary or secondary), energy conversion method (active or passive), and transduction principle used (resistive, capacitive, inductive, etc.). Examples of common transducers discussed include thermocouples, strain gauges, thermistors, and linear variable differential transformers. Selection factors and applications of transducers
This document discusses various types of mechanical sensors and their applications. It describes sensors that measure mechanical phenomena like pressure, force, torque, inertia, and flow. Pressure sensors are used in applications like manometers, barometers, microphones, and automotive parts. Force and torque sensors can be used in control systems, testing equipment, and for measuring power transmission. Inertial sensors like accelerometers have applications in industry, military, vibration monitoring, and safety systems. Flow sensors measure flow rates using principles of heat transfer and are used in microsensors and velocimetry applications. The document provides details on common sensing techniques like piezoresistivity, piezoelectricity, capacitive, inductive and resonant techniques.
Load cells are transducers that convert an applied force into an electrical signal. There are several types of load cells including resistive, capacitive, vibrating wire, piezoelectric, hydraulic, and pneumatic. Resistive load cells use strain gauges to measure deformation from applied forces. Capacitive load cells measure deformation capacitively. Vibrating wire load cells monitor loads in structural elements. Piezoelectric load cells generate voltage when force is applied to piezoelectric materials. Hydraulic load cells use fluid pressure from piston movement to measure force. Pneumatic load cells balance applied force with counteracting air pressure.
Longitudinal waves are waves where the medium oscillates in the direction of wave propagation. Sound is a longitudinal wave that travels through air by alternately compressing and rarefying the air. The speed of sound depends on the density and bulk modulus of the medium. Acoustic sensors like microphones convert pressure variations from sound waves into electrical signals. Common types include piezoelectric, capacitive, and resistive microphones. Surface acoustic wave sensors use interdigitated transducers on a piezoelectric substrate to generate and detect surface waves for sensing applications like pressure, strain, and temperature.
Ultrasound is produced by piezoelectric crystals in transducers that convert electrical pulses into sound waves and received echoes into electrical signals. Transducers operate in shock, burst, or continuous excitation modes. The piezoelectric crystals resonate at specific frequencies determined by their thickness and composition. Damping materials in transducers shorten pulse duration to improve image resolution by reducing echo overlap. Transducers use the pulse-echo principle to transmit sound pulses into the body and receive returning echoes to create ultrasound images.
Ultrasonography uses high frequency sound waves to produce images of internal organs and structures. Sound waves are transmitted into the body using a transducer, which converts electrical signals to sound and vice versa. Reflections from tissues are detected and used to construct images showing anatomical structures. Key physics principles include velocity, frequency, wavelength, and reflection based on acoustic impedance differences between tissues. Proper transducer design and focused beams are important for optimizing image quality and resolution.
This document discusses different types of sound sensors and transducers. It describes various audio to electrical sensors including moving coil microphones, moving iron microphones, and capacitor microphones. It explains how these different microphones work by converting sound wave vibrations into electrical signals using mechanisms like a vibrating diaphragm and magnets. The document also covers ultrasonic and infrasound sensors. It provides details on electrical to audio transducers and how speakers convert electrical signals back into sound waves.
1) The document is a lesson on acoustics that discusses sound fundamentals like frequency, wavelength, decibels and the human range of hearing.
2) It then covers acoustic concepts such as power, intensity, impedance and how they relate to a vibrating surface like a panel.
3) The document focuses on calculating the radiated acoustic power from a panel using Rayleigh's integral formulation and defines terms like transmission loss and radiation efficiency.
Ultrasound physics and image optimization1 (1)Prajwith Rai
This document discusses ultrasound physics and image optimization. It begins with an overview of basic principles, instrumentation, and image optimization techniques. It then describes how ultrasound works, including the generation of sound waves, their interaction with tissues through reflection, refraction, interference and absorption. This determines image quality. Instrumentation components like the transducer, transmitter, receiver and display are explained. Factors affecting the ultrasound beam like frequency, aperture, pulse length and coupling medium are also covered.
This document discusses ultrasound transducers and resolution. It begins by describing how ultrasound is produced and detected using a transducer composed of piezoelectric elements. Over time, transducers have evolved from single elements to arrays with hundreds of individual elements. The key components of a basic transducer are then outlined. The remainder of the document provides detailed explanations of piezoelectric materials, resonance transducers, damping blocks, matching layers, and the properties of transducer arrays including linear arrays and phased arrays. Beam properties such as the near field and far field are also defined.
Measurement and generation_of_underwater_soundsBharat Sharma
This document discusses electroacoustic transducers and their measurement and generation of underwater sounds. It begins by explaining that transducers convert electrical energy to acoustic energy and vice versa using piezoelectric, magnetostrictive, or electrodynamic principles. It then discusses the sensitivity and frequency response of piezoelectric elements, explaining that their response depends on factors like element size, material properties, and resonance frequency. Charts are provided showing examples of transducer sensitivity curves.
The document discusses ultrasonic testing techniques. It describes how ultrasonic pulses are transmitted into a material and reflections from internal imperfections or surfaces are detected. The time interval between pulse transmission and reception provides clues about the material's internal structure. Common techniques include pulse-echo testing and using transducers to generate and detect longitudinal or shear waves. Reflected signals are visualized on an oscilloscope as A-scans, B-scans, or C-scans to evaluate material features.
This document provides information on key audio concepts including:
- Wavelength and frequency describe properties of sound waves. Wavelength is the distance between wave cycles, and frequency is the number of cycles per second.
- Microphones convert sound waves to electrical signals. Different types and polar patterns have varying sensitivity and directionality.
- Audio signals have different levels from mic to line to speaker. Gain and attenuation adjust levels between devices.
- Equalizers, filters, compressors and other processors manipulate audio signals. Amplifiers power passive speakers to reproduce sound.
Ultrasound is produced by passing an electrical current through a piezoelectric crystal, causing it to expand and contract and generate sound waves above the human hearing range. The piezoelectric crystals in an ultrasound transducer convert electrical pulses into ultrasound pulses to image the body and then convert returning sound wave echoes back into electrical signals for processing. The frequency of the ultrasound determines the resolution and depth of penetration, with higher frequencies providing better resolution but shallower penetration.
This document discusses key topics in wireless transmission and mobile communications. It covers frequencies used for communication, signal propagation, antennas, modulation techniques, and multiplexing methods. The key topics are:
- Frequencies used for mobile communication range from VHF to EHF. Regulations assign different frequency bands for cellular networks, wireless LANs, and other technologies in different regions.
- Signals propagate through reflection, scattering, diffraction and other effects. This causes multipath propagation where the signal reaches the receiver along multiple paths. Mobility further influences signal propagation through short-term and long-term fading.
- Antennas used for mobile devices include simple dipoles and more directed antennas. Diversity combining uses multiple antennas
Ultrasonics uses elastic waves with frequencies above 20 kHz. Common applications include non-destructive testing in materials and medical diagnosis. Piezoelectric materials are often used to generate and detect ultrasonic waves due to the piezoelectric effect. Parameters like frequency, bandwidth, and transducer size must be selected appropriately for the application and material being tested.
Ultrasound uses sound waves to produce images of internal organs and tissues. Sound waves are transmitted into the body and the echoes produced by reflections from structures and tissues are detected. Three key points:
1) Ultrasound transducers convert electrical pulses into sound waves which penetrate the body and receive the echoes. Piezoelectric crystals in the transducer perform this function.
2) Reflected sound waves are displayed as images on screen to visualize internal structures. The brightness of each pixel depends on the strength of reflection.
3) Different transducer designs like linear arrays and curved arrays allow imaging of different body regions. Imaging modes like B-mode show anatomical structures while M-mode depicts motion.
Ultrasonic flow meters are commonly used in waste water treatment plants for the following reasons:
- They can measure flow in pipes carrying slurries and liquids with solids in suspension, which is common in waste water. Other meter types may clog or give inaccurate readings.
- Ultrasonic meters have no moving parts so they are not affected by abrasive particles in the flow which could damage mechanical meters.
- They can measure bi-directional or reverse flow which sometimes occurs in parts of the treatment process.
- Ultrasonic meters provide non-intrusive measurement without cutting into pipes. This avoids disruption to flow and prevents contamination.
- Many ultrasonic meters can operate using battery
Ultrasound uses high frequency sound waves to image internal structures. A transducer converts electrical pulses into ultrasound pulses and reflected sound waves back into electrical signals. Tissues reflect sound differently allowing visualization. Higher frequencies improve resolution but reduce penetration. Ultrasound has various medical uses like imaging fetuses, organs and detecting abnormalities by interpreting echo patterns. It provides real-time images without radiation unlike other modalities.
How to Add Chatter in the odoo 17 ERP ModuleCeline George
In Odoo, the chatter is like a chat tool that helps you work together on records. You can leave notes and track things, making it easier to talk with your team and partners. Inside chatter, all communication history, activity, and changes will be displayed.
How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
This document provides an overview of wound healing, its functions, stages, mechanisms, factors affecting it, and complications.
A wound is a break in the integrity of the skin or tissues, which may be associated with disruption of the structure and function.
Healing is the body’s response to injury in an attempt to restore normal structure and functions.
Healing can occur in two ways: Regeneration and Repair
There are 4 phases of wound healing: hemostasis, inflammation, proliferation, and remodeling. This document also describes the mechanism of wound healing. Factors that affect healing include infection, uncontrolled diabetes, poor nutrition, age, anemia, the presence of foreign bodies, etc.
Complications of wound healing like infection, hyperpigmentation of scar, contractures, and keloid formation.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
Leveraging Generative AI to Drive Nonprofit InnovationTechSoup
In this webinar, participants learned how to utilize Generative AI to streamline operations and elevate member engagement. Amazon Web Service experts provided a customer specific use cases and dived into low/no-code tools that are quick and easy to deploy through Amazon Web Service (AWS.)
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
How to Fix the Import Error in the Odoo 17Celine George
An import error occurs when a program fails to import a module or library, disrupting its execution. In languages like Python, this issue arises when the specified module cannot be found or accessed, hindering the program's functionality. Resolving import errors is crucial for maintaining smooth software operation and uninterrupted development processes.
Chapter wise All Notes of First year Basic Civil Engineering.pptxDenish Jangid
Chapter wise All Notes of First year Basic Civil Engineering
Syllabus
Chapter-1
Introduction to objective, scope and outcome the subject
Chapter 2
Introduction: Scope and Specialization of Civil Engineering, Role of civil Engineer in Society, Impact of infrastructural development on economy of country.
Chapter 3
Surveying: Object Principles & Types of Surveying; Site Plans, Plans & Maps; Scales & Unit of different Measurements.
Linear Measurements: Instruments used. Linear Measurement by Tape, Ranging out Survey Lines and overcoming Obstructions; Measurements on sloping ground; Tape corrections, conventional symbols. Angular Measurements: Instruments used; Introduction to Compass Surveying, Bearings and Longitude & Latitude of a Line, Introduction to total station.
Levelling: Instrument used Object of levelling, Methods of levelling in brief, and Contour maps.
Chapter 4
Buildings: Selection of site for Buildings, Layout of Building Plan, Types of buildings, Plinth area, carpet area, floor space index, Introduction to building byelaws, concept of sun light & ventilation. Components of Buildings & their functions, Basic concept of R.C.C., Introduction to types of foundation
Chapter 5
Transportation: Introduction to Transportation Engineering; Traffic and Road Safety: Types and Characteristics of Various Modes of Transportation; Various Road Traffic Signs, Causes of Accidents and Road Safety Measures.
Chapter 6
Environmental Engineering: Environmental Pollution, Environmental Acts and Regulations, Functional Concepts of Ecology, Basics of Species, Biodiversity, Ecosystem, Hydrological Cycle; Chemical Cycles: Carbon, Nitrogen & Phosphorus; Energy Flow in Ecosystems.
Water Pollution: Water Quality standards, Introduction to Treatment & Disposal of Waste Water. Reuse and Saving of Water, Rain Water Harvesting. Solid Waste Management: Classification of Solid Waste, Collection, Transportation and Disposal of Solid. Recycling of Solid Waste: Energy Recovery, Sanitary Landfill, On-Site Sanitation. Air & Noise Pollution: Primary and Secondary air pollutants, Harmful effects of Air Pollution, Control of Air Pollution. . Noise Pollution Harmful Effects of noise pollution, control of noise pollution, Global warming & Climate Change, Ozone depletion, Greenhouse effect
Text Books:
1. Palancharmy, Basic Civil Engineering, McGraw Hill publishers.
2. Satheesh Gopi, Basic Civil Engineering, Pearson Publishers.
3. Ketki Rangwala Dalal, Essentials of Civil Engineering, Charotar Publishing House.
4. BCP, Surveying volume 1
This presentation includes basic of PCOS their pathology and treatment and also Ayurveda correlation of PCOS and Ayurvedic line of treatment mentioned in classics.
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1. Sensing and Sensors: Acoustic Sensors
version 1.1
MediaRobotics Lab, January 2008
Background: sound waves
Sound waves are created by alternate compression and expansion of solids, liquids or
gases at certain frequencies.
Longitudinal mechanical waves: oscillation in the direction of wave propagation
'Sound' are longitudinal mechanical waves between 20 and 20khz, based only on our
own hearing abilities / limitations... Mechanical waves below 20hz. Are perceived by
dogs and called Infrasound by humans.
Check your hearing and your audio equipment here:
http://www.audiocheck.net/audiotests_frequencychecklow.php
References:
Fraden: Handbook of Modern Sensors
Drafts, Acoustic Wave Sensors
Buff, SAW Sensors
Cady. Piezoelectricity: An Introduction to the Theory and Applications
of Electromechanical Phenomena in Crystals.
2. The Speed of Sound
The speed of sound depends on the medium through which the waves are passing, and
is often quoted as a fundamental property of the material. In general, the speed of sound
is proportional to the square root of the ratio of the elastic modulus (stiffness) of the
medium to its density. Those physical properties and the speed of sound change with
ambient conditions.
For example, the speed of sound in gases depends on temperature. In air at sea level,
the speed of sound is approximately 343 m/s, in water 1482 m/s, and in steel about
5960 m/s (at 20 °C). The speed of sound is also slightly sensitive (a second-order effect)
to the sound amplitude, which means that there are nonlinear propagation effects, such
as the production of harmonics and mixed tones not present in the original sound.
http://en.wikipedia.org/wiki/Sound
3. Sound as an waveform can be described in terms of its energy and the
frequencies it can be decomposed into
sound wave of a human voice
in the time domain
4. Signals are converted from time or space domain to the frequency domain usually
through the Fourier transform. The Fourier transform(s) describe a decomposition of a
function in terms of a sum of sinusoidal functions (basis functions) of different
frequencies that can be recombined to obtain the original function.
The Fourier transform and its various derivatives form an important part of the art and
science of digital signal processing (more on this later in the course).
S(t) =
50mV . sin (2 pi 1000 t + pi/2) +
100mV . sin (2 pi 2000 t + 0 ) +
100mV . sin (2 pi 3000 t + 0 ) + ..... + ....
http://www.4p8.com/eric.brasseur/fouren.html
5. Human voice signal (5 seconds) and the corresponding frequency componets
http://en.wikipedia.org/wiki/Frequency_spectrum
7. Sound as a qualitative measure is often described as having the following components
"Music components":
* Pitch
* Timbre
* Harmonics
* Loudness
* Rhythm
"Sound envelope components":
* Attack
* Sustain
* Decay
8. The pitch of a sound is determined by the frequency of the sound.
* low (bass) - sounds of thunder and gunshots
* midrange - a telephone ringing
* high (treble) - small bells and cymbals
Timbre is that unique combination of fundamental frequency, harmonics, and overtones
that gives each voice, musical instrument, and sound effect its unique coloring and
character.
The harmonic of a wave is a component frequency of the signal that is an integer multiple
of the fundamental frequency.
1f
2f
3f
4f
440 Hz
880 Hz
1320 Hz
1760 Hz
fundamental frequency
first overtone
second overtone
third overtone
first harmonic
second harmonic
third harmonic
fourth harmonic
Rhythm is a recurring sound that alternates between strong and weak elements
9. Envelope of a sound
peak
loudness
[dB]
time [seconds]
attack
sustain
decay
10. Loudness, a subjective measure, is not equivalent to objective measures of sound
pressure such as decibels or intensity. Research suggests that the human auditory system
integrates intensity over a 600-1000 ms window.
The abstraction of loudness is sound intensity. Like several other physical properties (light
and noise) sound intensity is measured in decibel, a logarithmic scaling. The decibel scale
linearizes a physical value in which exponential changes of magnitude are perceived by
humans as being more or less linearly related; a doubling of actual intensity causes
perceived intensity to always increase by roughly the same amount, irrespective of the
original intensity level.
sound intensity is described by convention in Decibels : β=10 log10 P1/ P0
where the unit of β is the decibel (dB) and p0=10−12 W / m2 , the 'sound threshold'
Example: 30dB is the ratio between a base sound and a sound 1000 times more intensive
10 log10 1000W /1 W =30dB
Here some notable sound levels
Threshold of hearing
heavy traffic
Niagara Falls
threshold of pain
hydraulic press at 1m
0dB (β = 0)
80 dB
85 dB
120dB
130dB
11. Microphones
Microphone: acoustic sensors for air waves in the audible range
Hydrophone: acoustic sensor for liquid waves
microphone / hydrophone are pressure sensors with a wide dynamic range...
A microphone / hydrophone is a pressure transducer, adapted for the transduction of sound /
liquid waves.
All microphones / hydrophones have a moving diaphragm and a displacement tranducer that
converts this motion into an electric signal.
Microphones / hydrophones differ by :
sensitivity, direction characteristics, frequency bandwidth, dynamic range
12. condensor microphones / capacitive microphones
background: capacitance, charge and voltage across two conducting plates a distance d apart
area A
+
+
+
+
+
+
+
+
+
+
+
+
voltage V
-
distance d
+q
-q
V = q∗d /em∗e0∗A
em: material constant
e0: permitivity constant
−12C2
8.8542∗10
/ Nm
2
13. A capacitive microphone linearly converts a distance between plates into an electric voltage.
The device requires a source of electric charge (q) whose magnitude directly determines the
microphone sensitivity.
Many capacitive / condenser microphones are fabricated of silicon diaphragms that convert
the acoustic pressure of the sound wave into a (distance) displacement
Mechanical feedback:
improves the frequency
range of the microphone,
but reduces deflection ->
lower sensitivity
14. fiber-optic microphones
Preferable where capacitive measurements are impossible (inside a rocket engine)
Design: a single-mode temperature insensitive interferometer + reflective plate diaphragm.
The interferometer emits a laser beam that is used to detect the plate deflection which is
directly related to the acoustic pressure. The phase of the reflected light will vary and differ
from that of the (reflected reference light). Since both sensing and reference light travel in
the same light guide, they interfere resulting in light intensity modulation.
Such microphones can detect diaphragm movement in the order of 10−10 m
15. piezoelectric microphones
background: the piezoelectric effect
A piezoelectric crystal is a direct converter of mechanical stress to electric charge.
When compressed or pulled, a piezoelectric crystal will build up alternate charges on
opposite faces, thus acting like a capacitor with an applied voltage. A current
(piezoelectricity) can then be generated between the faces.
When subjected to an external voltage, the crystal will expand or contract accordingly.
1880 - 1882
The first experimental demonstration of a connection between macroscopic
piezoelectric phenomena and crystallographic structure was published in 1880 by
Pierre and Jacques Curie.
Their experiment consisted of a conclusive measurement of surface charges
appearing on specially prepared crystals (tourmaline, quartz, topaz, cane sugar {sic}
and Rochelle salt) subjected to mechanical stress. These results were obtained using
tinfoil, glue, wire, magnets and a jeweler's saw.
Other areas of scientific phenomenological experience that were noted around the
same time:
"contact electricity" (friction from static electricity)
"pyroelectricity" (electricity from crystals via heating)
http://www.designinfo.com/kistler/ref/tech_theory_text.htm
http://www.piezo.com/tech4history.html
19. Today piezoceramics are preferred as there specifications can be more
tightly controlled (and synthesized). Also, piezoceramics can operate up
to higher frequencies.
Typically, a piezoelectric disk with two electrodes serves as the input to a
high impedance amplifier. Incoming acoustic waves generate
mechanical stress in the disk and a corresponding piezoelectric current.
20. Electret microphones
An electret microphone is a permanently electrically polarized crystalline dielectric material. It
is an electrostatic transducer consisting of metalized electret and a backplate separated from
the diaphragm by an air gap.
21. Because the electret is permanently electrically polarized, there is an electric
field in the air gap. When an acoustic wave hits the device, the air gap is altered
(reduced):
V =s∗ds/e0 se∗s1
Fraden states (after a few derivations) that the sensitivity does not depend on the area
of the dielectric.
fr=1/ 2pi∗ po/ so∗M
M: mass of membrane
po: atmospheric pressure
so: effective thickness of membrane
This frequency should be set such that it is larger than the highest frequency to
which the microphone is expected to properly respond.
Electret microphones do not require a DC bias voltage for operation.
22. Acoustic wave sensors
Acoustic wave sensors are so named because their detection mechanism is a
mechanical, or acoustic, wave. As the acoustic wave propagates through or on
the surface of the material, any changes to the characteristics of the propagation
path affect the velocity and/or amplitude of the wave. Changes in velocity can be
monitored by measuring the frequency or phase characteristics of the sensor and
can then be correlated to the corresponding physical quantity being measured.
Virtually all acoustic wave devices and sensors use a piezoelectric material to
generate the acoustic wave. Piezoelectricity refers to the production of electrical
charges by the imposition of mechanical stress. The phenomenon is reciprocal.
Applying an appropriate electrical field to a piezoelectric material creates a
mechanical stress. Piezoelectric acoustic wave sensors apply an oscillating
electric field to create a mechanical wave, which propagates through the
substrate and is then converted back to an electric field for measurement.
Among the piezoelectic substrate materials that can be used for acoustic wave
sensors and devices, the most common are quartz (SiO2), lithium tantalate
(LiTaO3), and, to a lesser degree, lithium niobate (LiNbO3). An interesting
property of quartz is that it is possible to select the temperature dependence of
the material by the cut angle and the wave propagation direction.
23. The advantage of using acoustic
waves (vs electromagnetic waves) is
the slow speed of propagation (5
orders of magnitude slower). For the
same frequency, therefore, the
wavelength of the elastic wave is
100,000 times shorter than the
corresponding
electromagnetic
shortwave.
This allows for the fabrication of very
small sensors with frequencies into
the gigahertz range with very fast
response times.
Solid state acoustic detectors have
the electric circuit coupled to the
mechanical structure where the
waves propagate.
The sensor generally has two
(piezoelectric) transducers at each
end. One at the transmitting end
(generator) and one at the receiving
end (receiver) where the wave is
converted into an electric signal.
24. A typical acoustic wave device consists of two sets of interdigital transducers. One
transducer converts electric field energy into mechanical wave energy; the other converts
the mechanical energy back into an electric field.
Influence on SAW sensors
SOURCE:
W. Buff, SAW SENSORS FOR DIRECT AND REMOTE MEASUREMENT