Microphones 101 - a Brief Guide
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A GUIDE to USING FETS for SENSOR APPLICATIONS by Ron Quan
Three Decades of Quality Through Innovation A GUIDE TO USING FETS FOR SENSOR APPLICATIONS By Ron Quan Linear Integrated Systems • 4042 Clipper Court • Fremont, CA 94538 • Tel: 510 490-9160 • Fax: 510 353-0261 • Email: [email protected] A GUIDE TO USING FETS FOR SENSOR APPLICATIONS many discrete FETs have input capacitances of less than 5 pF. Also, there are few low noise FET input op amps Linear Systems that have equivalent input noise voltages density of less provides a variety of FETs (Field Effect Transistors) than 4 nV/ 퐻푧. However, there are a number of suitable for use in low noise amplifier applications for discrete FETs rated at ≤ 2 nV/ 퐻푧 in terms of equivalent photo diodes, accelerometers, transducers, and other Input noise voltage density. types of sensors. For those op amps that are rated as low noise, normally In particular, low noise JFETs exhibit low input gate the input stages use bipolar transistors that generate currents that are desirable when working with high much greater noise currents at the input terminals than impedance devices at the input or with high value FETs. These noise currents flowing into high impedances feedback resistors (e.g., ≥1MΩ). Operational amplifiers form added (random) noise voltages that are often (op amps) with bipolar transistor input stages have much greater than the equivalent input noise. much higher input noise currents than FETs. One advantage of using discrete FETs is that an op amp In general, many op amps have a combination of higher that is not rated as low noise in terms of input current noise and input capacitance when compared to some can be converted into an amplifier with low input discrete FETs. -
Introduction to Electrets: Principles, Equations, Experimental Techniques
Introduction to electrets: Principles, equations, experimental techniques Gerhard M. Sessler Darmstadt University of Technology Institute for Telecommunications Merckstrasse 25, 64283 Darmstadt, Germany [email protected] Darmstadt University of Technology • Institute for Telecommunications Overview Principles Charges Materials Electret classes Equations Fields Forces Currents Charge transport Experimental techniques Charging Surface potential Thermally-stimulated discharge Dielectric measurements Charge distribution (surface) Charge distribution (volume) Darmstadt University of Technology • Institute for Telecommunications Electret charges Darmstadt University of Technology • Institute for Telecommunications Energy diagram and density of states for a polymer Darmstadt University of Technology • Institute for Telecommunications Electret materials Polymers Anorganic materials Fluoropolymers (PTFE, FEP) Silicon oxide (SiO 2) Polyethylene (HDPE, LDPE, XLPE) Silicon nitride (Si 3N4) Polypropylene (PP) Aluminum oxide (Al 2O3) Polyethylene terephtalate (PET) Glas (SiO 2 + Na, S, Se, B, ...) Polyimid (PI) Photorefractive materials Polymethylmethacrylate (PMMA) • Polyvinylidenefluoride (PVDF) • Ethylene vinyl acetate (EVA) • • • Cellular and porous polymers Cellular PP Porous PTFE Darmstadt University of Technology • Institute for Telecommunications Charged or polarized dielectrics Category Materials Charge or polarization Properties Applications Density Geometry [mC/m2 ] Real-charge External electric FEP, SiO electrets 2 0.1 - 1 field -
Transducers and Sensors
3/7/2017 TRANSDUCERS AND SENSORS Dr. Ibrahim Al-Naimi Closed‐loop Control System 1 3/7/2017 CHAPTER ONE Introduction Functional Elements of a Measurement System • Basic Functional Elements 1‐Transducer Element 2‐ Signal Conditioning Element 3‐ Data Presentation Element • Auxiliary Functional Elements A‐ Calibration Element B‐ External Power supply 2 3/7/2017 Functional Elements of a Measurement System Transducer and Signal Conditioning 3 3/7/2017 Transducer Element • The Transducer is defined as a device, which when actuated by one form of energy, is capable of converting it to another form of energy. The transduction may be from mechanical, electrical, or optical to any other related form. • The term transducer is used to describe any item which changes information from one form to another. Transducer Element • The Transducer element normally senses the desired input in one physical form and convert it to an output in another physical form. For example, the input variable to the transducer could be pressure, acceleration, or temperature and the output of transducer may be disp lacemen t, voltage, or resitistance change depending on the type of transducer element. 4 3/7/2017 Transducer Element • Single stage • Double stage Single Stage Transducer 5 3/7/2017 Double Stage Transducer Typical Examples of Transducer Elements 6 3/7/2017 Typical Examples of Transducer Elements Typical Examples of Transducer Elements 7 3/7/2017 Transducers classification • Based on power type classification ‐ Active transducer (Diaphragms, Bourdon Tubes, tachometers, piezoelectric, etc…) ‐ Passive transducer (Capacitive, inductive, photo, LVDT, etc…) Transducers classification • Based on the type of output signal ‐ Analogue Transducers (stain gauges, LVDT, etc…) ‐ Digital Transducers (Absolute and incremental encoders) 8 3/7/2017 Transducers classification • Based on the electrical phenomenon or parameter tha t may be chdhanged due to the whole process. -
Note PERFORMANCE of ELECTRET IONIZATION CHAMBERS IN
Note PERFORMANCE OF ELECTRET IONIZATION CHAMBERS IN MAGNETIC FIELD P. Kotrappa,* L. R. Stieff,* T. F. Mengers,† and R. D. Shull† The change in charge is measured using a portable charge Abstract—Electret ionization chambers are widely used for reader and is the measure of the integrated ionization measuring radon and radiation. The radiation measured in- cludes alpha, beta, and gamma radiation. These detectors do over the sampling period. These chambers are widely not have any electronics and as such can be introduced into used for measuring radon in air (Kotrappa et al. 1990) magnetic field regions. It is of interest to study the effect of and environmental gamma radiation (Fjeld et al. 1994; magnetic fields on the performance of these detectors. Relative Hobbs et al. 1996). These chambers are also used for responses are measured with and without magnetic fields present. Quantitative responses are measured as the magnetic measuring alpha and beta contamination levels (Kasper field is varied from 8 kA/m to 716 kA/m (100 to 9,000 gauss). 1999; Kotrappa et al. 1995). One feature of these No significant effect is observed for measuring alpha radiation detectors, which makes them unique, is that there are no and gamma radiation. However, a significant systematic effect electronic components or power supply associated with is observed while measuring beta radiation from a 90Sr-Y source. Depending upon the field orientation, the relative the detectors. Because of this property, these detectors response increased from 1.0 to 2.7 (vertical position) and can be used in areas with magnetic fields present without decreased from 1.0 to 0.60 (horizontal position). -
AEA-KU5A-Owners-Manual-Rev1.Pdf
AEA KU5A OWNER’S MANUAL ACTIVE CARDIOID END-ADDRESS RIBBON MIC WELCOME We congratulate you on your purchase of the AEA KU5A ribbon microphone and welcome you to the AEA family. Never before has a ribbon mic delivered such directionality and uncompromised tonality in a package so fit for both studio and live settings. The KU5A is ideal for studio and live applications where both superior rejection and classic ribbon tonality are paramount. Whether recording a vocal, guitar, or even a snare drum, the KU5A delivers brilliant, focused sound where other conventional ribbons can’t. From close range the KU5A retains the hefty low end and pronounced midrange one expects of AEA ribbons and with manageable proximity effect. Vocalists can sing directly into the grille of the KU5A because its interior components are the most protected of any in the AEA lineup. The rugged KU5A is equipped with active electronics, so it’s suited or any preamp in the studio and on the road. Your KU5A microphone is 100% handcrafted in Pasadena, CA. AEA is an independent, family owned company with a small crew of skilled technicians – many of whom are themselves, musicians. We manufacture all our ribbon microphones and preamps with locally sourced parts. We hope your microphone will capture many magical performances that touch the heart. This manual will help ensure that you get the best sound and longevity from your new microphone. Please become part of the AEA community by sharing your experiences via e-mail, phone or social media. Wes Dooley President of AEA 2 CONTENTS 2 WELCOME 4 INTRODUCTION 4 SUPPORT 5 GENERAL GUIDELINES 7 APPLICATION ADVICE 10 SPECIFICATIONS 3 INTRODUCTION The KU5A is an end-address, phantom-powered, supercardioid ribbon microphone. -
Transducers in Audio ● Transducer: Any Mechanism That Transforms One Form of Energy Into Another Form of Energy
Transducers in Audio ● Transducer: Any mechanism that transforms one form of energy into another form of energy. ○ Physical energy into mechanical energy ○ Physical energy into electrical energy ○ Mechanical energy into electrical energy ○ Vice versa Audio is primarily concerned with turning physical acoustic energy into electrical energy and back again. What are our two most basic audio transducers? scienceaid.net https://socratic.org/questions/what-part-of-the-ear-contains-the-sensory-receptors-for-hearing From Acoustic to Electric Energy First...a short trip into basic electrical theory... Michael Faraday http://www.rigb.org/our-history/michael-faraday Electro-magnetism Faraday’s Law of Induction: Basically, any change in the magnetic field of a coil of wire will cause a voltage to be induced in a wire. Conversely, any change in the voltage on a coil of wire will cause the magnetic field to change. This is called electromagnetism, and the field created is called an electro-magnetic field. Capacitance When two conductors are given an opposite charge, an electric or more specifically a capacitive field is generated around them. When the relationship between the two conductors (for example the distance between them) changes it causes measurable effects on the charges. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/imgele/cap.png Capacitance When two conductors are given an opposite charge, a electric or more specifically a capacitive field is generated around them. When the relationship between the two conductors, for example the distance between them, changes is causes measurable effects on the charges. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/imgele/cap.png ● Alternating Current (AC) vs Direct Current (DC) ○ AC charge changes from positive to negative across the zero axis. -
Bachelor Thesis
BACHELOR THESIS Relationship Between Distance and Microphone Directivity in a Speaker Booth Björn Samuelsson 2015 Bachelor of Arts Audio Engineering Luleå University of Technology Department of Arts, Communication and Education Relationship between distance and microphone directivity in a speaker booth Abstract A study was made to investigate trained listeners preferences regarding a microphone's directivity and distance from a speaker when listening to a voice recorded in a speaker booth. Two directivities (omnidirectional and cardioid) and three distances (5, 25 and 52 cm) were tested on 19 subjects in a multiple comparison listening test regarding their preference and five other attributes taken from earlier studies. The result showed that an omnidirectional microphone placed close to a source might be preferable over a cardioid at the same distance or a cardioid placed a bit away from the source. The omnidirectional microphone however tends to perform more even at different distances compared to a cardioid, which makes it easier for a engineer to find a good microphone position for it. Table of Content Acknowledgements..........................................................................................................3 1. Introduction.....................................................................................................................4 1.1. Aim............................................................................................................................4 1.2. Research question....................................................................................................4 -
How to Make an Electret the Device That Permanently Maintains an Electric Charge by C
How to Make an Electret the Device That Permanently Maintains an Electric Charge by C. L. Strong Scientific America, November, 1960 Danger Level 4: (POSSIBLY LETHAL!!) Alternative Science Resources World Clock Synthesis Home --------------------- THE HISTORY OF SCIENCE IS A TREASURE house for the amateur experimenter. For example, many devices invented by early workers in electricity and magnetism attract little attention today because they have no practical application, yet these devices remain fascinating in themselves. Consider the so-called electret. This device is a small cake of specially prepared wax that has the property of permanently maintaining an electric field; it is the electrical analogue of a permanent magnet. No one knows in precise detail how an electret works, nor does it presently have a significant task to perform. George O. Smith, an electronics specialist of Rumson, N.J., points out, however, that this is no obstacle to the enjoyment of the electret by the amateur. Moreover, the amateur with access to a source of high-voltage current can make an electret at virtually no cost. "For more than 2,000 years," writes Smith, "it was suspected that the magnetic attraction of the lodestone and the electrostatic attraction of the electrophorus were different manifestations of the same phenomenon. This suspicion persisted from the time of Thales of Miletus (600 B.C.) to that of William Gilbert (A.D. 1600). After the publication of Gilbert's treatise De Magnete, the suspicion graduated into a theory that was supported by many experiments conducted to show that for every magnetic effect there was an electric analogue, and vice versa. -
Proximity Effect Detection for Directional Microphones
Audio Engineering Society Convention Paper 8475 Presented at the 131st Convention 2011 October 20–23 New York, USA This Convention paper was selected based on a submitted abstract and 750-word precis that have been peer reviewed by at least two qualified anonymous reviewers. The complete manuscript was not peer reviewed. This convention paper has been reproduced from the author’s advance manuscript without editing, corrections, or consideration by the Review Board. The AES takes no responsibility for the contents. Additional papers may be obtained by sending request and remittance to Audio Engineering Society, 60 East 42nd Street, New York, New York 10165-2520, USA; also see www.aes.org. All rights reserved. Reproduction of this paper, or any portion thereof, is not permitted without direct permission from the Journal of the Audio Engineering Society. Proximity effect detection for directional microphones Alice Clifford1 and Joshua D. Reiss1 1Queen Mary University of London, London, E1 4NS, UK Correspondence should be addressed to Alice Clifford ([email protected]) ABSTRACT The proximity effect in directional microphones is characterised by an undesired boost in low frequency energy as the source to microphone distance decreases. Traditional methods for reducing the proximity effect use a high pass filter to cut low frequencies which alter the tonal characteristics of the sound and are not dependent on the input source. This paper proposes an intelligent approach to detect the proximity effect in a single capsule directional microphone in real time. The low frequency boost is detected by analysing the spectral flux of the signal over a number of bands over time. -
Basic Physics of Ultrasonographic Imaging
BASIC PHYSICS OF ULTlVlSONOGRAPHIC IMAGING Diagnostic Imaging and Laboratory Technology Essential Health Technologies Health Technology and Pharmaceuticals WORLD HEALTH ORGANIZATION Geneva BASIC PHYSICS OF ULTRASONOGRAPHIC IMAGING Editor Harald Ostensen Author Nimrod M. Tole, Ph.D. Associate Professor of Medical Physics Department of Diagnostic Radiology University of Nairobi WORLD HEALTH ORGANIZATION WHO Library Cataloguing-in-Publication Data Tole, Nimrod M. Basic physics of ultrasonic imaging / by Nimrod M. Tole. 1. Ultrasonography I. Title. ISBN 92 41592990 (NLM classification: WN 208) © World Health Organization 2005 All rights reserved. Publications of the World Health Organization can be obtained from WHO Press, World Health Organization, 20 Avenue Appia, 1211 Geneva 27, Switzerland (tel: +41 22 791 2476; fax: +41 22791 4857; email: [email protected]). Requests for permission to reproduce or translate WHO publications - whether for sale or for noncommercial distribution - should be addressed to WHO Press, at the above address (fax: +41 22791 4806; email: [email protected]). The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dotted lines on maps represent approximate border lines for which there may not yet be full agreement. The mention of specific companies or of certain manufacturers' products does not imply that they are endorsed or recommended by the World Health Organization in preference to others of a similar nature that are not mentioned. -
Chapter 1 Introduction to Measurement Systems
4/3/2019 Advanced Measurement Systems and Sensors Dr. Ibrahim Al-Naimi Chapter one Introduction to Measurement Systems 1 4/3/2019 Outlines • Control and measurement systems • Transducer/sensor definition and classifications • Signal conditioning definition and classifications • Units of measurements • Types of errors • Transducer/sensor transfer function • Transducer characteristics • Statistical analysis Closed-loop Control System 2 4/3/2019 Measurement System Transducer and Signal Conditioning 3 4/3/2019 Transducer Element • The Transducer is defined as a device, which when actuated by one form of energy, is capable of converting it to another form of energy. The transduction may be from mechanical, electrical, or optical to any other related form. • The term transducer is used to describe any item which changes information from one form to another. Transducer and Sensor • Transducers are elements that respond to changes in the physical condition of a system and deliver output signals related to the measured, but of a different form and nature. • Sensor is the initial stage in any transducer. • The property of transducer element is affected by the variation of the external physical variable according to unique relationship. 4 4/3/2019 Transducers classification • Based on power type classification - Active transducer (Diaphragms, Bourdon Tubes, tachometers, piezoelectric, etc…) - Passive transducer (Capacitive, inductive, photo, LVDT, etc…) Transducers classification • Based on the type of output signal - Analogue Transducers (stain -
Maximizing Efficiency in Active Loudspeaker Systems
Maximizing Efficiency in Active Loudspeaker Systems Wolfgang Klippel, KLIPPEL GmbH, Dresden, Germany Increasing the efficiency of the electro-acoustical conversion is the key to modern audio devices generating the required sound output with minimum size, weight, cost and energy. There is unused potential for increasing the efficiency of the electro-dynamical transducer by using a nonlinear motor topology, a soft suspension and cultivating the modal resonances in the mechanical and acoustical system. However, transducers optimized for maximum efficiency are more prone to nonlinear and unstable behavior. Nonlinear adaptive control can compensate for the undesired signal distortion, protect the transducer against overload, stabilize the voice coil position and cope with time varying properties of the suspension. The paper discusses the design of modern active systems that combine the new opportunities provided by software algorithms with the optimization of the hardware components in the transducer and power amplifier. reducing power consumption in portable 1 Introduction applications with limited battery capacity. The user of loudspeakers, headphone and other For this discussion, the paper provides new audio devices expects that the audio signal can be definitions of the efficiency to consider the influence reproduced at sufficient amplitude and quality but of the spectral properties of the complex audio prefers products which are smaller, lighter, less cost signals (e.g. music). The paper explains the intensive and provide a longer stand-alone operation difference between efficiency and voltage in personal applications. sensitivity, which is a second important Creating such an audio product requires a characteristic of the transducer required to match the combination of hardware and software components transducer with the power amplifier.