Lecture

Capacitive Microphones

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In course

MICRO-330: Sensors

Principes physiques et électronique utilisés dans les capteurs. Applications des capteurs. ...

Description

This lecture covers the construction and operation of capacitive microphones, focusing on the variation of capacitance as the relevant quantity for measurement. It explains the construction of a capacitive microphone, the concept of electret microphones, and the presence of electrets allowing quasi-permanent polarization. The lecture also discusses the special circuit for electret microphones, including the need for a power supply to recharge them, and the advantages and disadvantages of using electret microphones.

Instructors (3)

Philippe Renaud

Philippe Renaud is Professor at the Microsystem Laboratory (LMIS4) at EPFL. He is also the scientific director of the EPFL Center of MicroNanoTechnology (CMI). His main research area is related to micronano technologies in biomedical applications (BioMEMS) with emphasis on cell-chips, nanofluidics and bioelectronics. Ph. Renaud is invloved in many scientifics papers in his research area. He received his diploma in physics from the University of Neuchâtel (1983) and his Ph.D. degree from the University of Lausanne (1988). He was postdoctoral fellow at University of California, Berkeley (1988-89) and then at the IBM Zürich Research Laboratory in Switzerland (1990-91). In 1992, he joined the Sensors and Actuators group of the Swiss Center for Electronics and Microtechnology (CSEM) at Neuchâtel, Switzerland. He was appointed assistant professor at EPFL in 1994 and full professor in 1997. In summer 1996, he was visiting professor at the Tohoku University, Japan. Ph. Renaud is active in several scientific committee (scientific journals, international conferences, scientific advisory boards of companies, PhD thesis committee). He is also co-founder of the Nanotech-Montreux conference. Ph. Renaud is committed to valorization of basic research through his involvement in several high-tech start-up companies.

Giovanni Boero

Expertise Nuclear magnetic resonance (NMR), Electron spin resonance (ESR), Ferromagnetic resonance (FMR), RF/MW discrete and integrated electronics, Magnetic sensors, Noise phenomena. Mission Methods based on the magnetic resonance of nuclear spins (nuclear magnetic resonance (NMR)), unpaired electrons spins (electron spin resonance (ESR)), and coupled electron spins electrons (ferromagnetic resonance (FMR)) are very powerful radiofrequency/microwave spectroscopy tools used in many research and industrial a

Herbert Shea

Expertise soft robotics, wearable haptics, electrostatic actuators, EHD Mission My lab develops flexible polymer-based actuators for a wide range of applications including haptics and soft robotics. More info at https://www.epfl.ch/labs/lmts/ Links from EPFL-LMTS Lab webpage People Research ActivitiesPublications TeachingPublications and Conference papers Link to my lab Education PhD | Physics 1997 – 1997 Harvard University MA | Physics 1993 – 1993 Harvard University

Official source

Related concepts (24)

RL circuit

A resistor–inductor circuit (RL circuit), or RL filter or RL network, is an electric circuit composed of resistors and inductors driven by a voltage or current source. A first-order RL circuit is composed of one resistor and one inductor, either in series driven by a voltage source or in parallel driven by a current source. It is one of the simplest analogue infinite impulse response electronic filters. The fundamental passive linear circuit elements are the resistor (R), capacitor (C) and inductor (L).

RLC circuit

An RLC circuit is an electrical circuit consisting of a resistor (R), an inductor (L), and a capacitor (C), connected in series or in parallel. The name of the circuit is derived from the letters that are used to denote the constituent components of this circuit, where the sequence of the components may vary from RLC. The circuit forms a harmonic oscillator for current, and resonates in a manner similar to an LC circuit. Introducing the resistor increases the decay of these oscillations, which is also known as damping.

Construction

Construction is a general term meaning the art and science to form objects, systems, or organizations, and comes from Latin constructio (from com- "together" and struere "to pile up") and Old French construction. To construct is the verb: the act of building, and the noun is construction: how something is built, the nature of its structure. In its most widely used context, construction covers the processes involved in delivering buildings, infrastructure, industrial facilities, and associated activities through to the end of their life.

Polarization (physics)

Polarization (also polarisation) is a property of transverse waves which specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave. A simple example of a polarized transverse wave is vibrations traveling along a taut string (see image); for example, in a musical instrument like a guitar string. Depending on how the string is plucked, the vibrations can be in a vertical direction, horizontal direction, or at any angle perpendicular to the string.

RC circuit

A resistor–capacitor circuit (RC circuit), or RC filter or RC network, is an electric circuit composed of resistors and capacitors. It may be driven by a voltage or current source and these will produce different responses. A first order RC circuit is composed of one resistor and one capacitor and is the simplest type of RC circuit. RC circuits can be used to filter a signal by blocking certain frequencies and passing others.

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