Abstract: A device for protecting a microphone sensing surface, such as a diaphragm, from the detrimental effects of the ambient environment. The device incorporates a perforated surface to protect the microphone and in conjunction with a chamber volume creates an acoustic resonance in the 1 kHz to 20 kHz spectrum, which improves the microphone signal-to-noise ratio performance. The microphone is acoustically coupled to the chamber volume for sensing pressure of the ambient environment. There is no line of sight to the microphone sensing surface from the ambient environment, so that rain, wind and sand have no direct path to the microphone sensing surface. The perforations of the outer surface are small to prevent objects from contacting the microphone sensing surface via a direct path. Water drains from the chamber volume and does not become trapped if an embodiment of the invention is temporarily submerged so that the microphone returns to normal operation quickly.

Abstract: A MEMS microphone has a backplate with a given backplate aperture, and a diaphragm having a diaphragm aperture. The given backplate aperture is substantially aligned with the diaphragm aperture.

Abstract: A MEMS microphone has a stationary portion with a backplate having a plurality of apertures, and a diaphragm spaced from the backplate and having an outer periphery. As a condenser microphone, the diaphragm and backplate form a variable capacitor. The microphone also has a post extending between, and substantially permanently connected with, both the backplate and the diaphragm, and a set of springs securing the diaphragm to at least one of the post and the stationary portion. The post is positioned to be radially inward of the outer periphery of the diaphragm.

Abstract: A gas sensor having a micro-package structure includes a light-emitting unit, a light-receiving unit, and a signal-processing unit all deposited on a substrate, and a package body fixed to the substrate and having a chamber and a through hole. The chamber accommodates all the units and the through hole is over the substrate. Gas enters the chamber through the through hole. The light-emitting unit emits an optical signal that passes through the gas and then is received by the light-receiving unit. Then a signal-processing unit electrically connected to the light-receiving unit performs spectral analysis. Thereby, the gas sensor is advantageous for requiring low packaging costs and being compact.

Abstract: The invention relates to a miniaturized electrical component comprising an MEMS chip and an ASIC chip. The MEMS chip and the ASIC chip are disposed on top of each other; an internal mounting of MEMS chip and ASIC chip is connected to external electrical terminals of the electrical component by means of vias through the MEMS chip or the ASIC chip.

Abstract: Measures for improving the acoustic properties of a microphone component produced in sacrificial layer technology. The micromechanical microphone structure of such a component is implemented in a layered structure, and includes at least one diaphragm, which is deflectable by sound pressure and which is implemented in a diaphragm layer, and a stationary acoustically permeable counterelement for the diaphragm which is implemented in a thick functional layer above the diaphragm layer and which is provided with through openings for introducing sound. The through openings for introducing sound are situated above the middle region of the diaphragm, while perforation openings which are largely acoustically passive are provided in the counterelement, above the edge region of the diaphragm.

Abstract: A dual-diaphragm acoustic transducer includes a substrate defining an opening, an inner diaphragm and an outer diaphragm concentrically mounted at one same side of the substrate corresponding to the opening of the substrate, and a plurality of elastic supporting members connected between the outer perimeter of the inner diaphragm and the inner perimeter of the outer diaphragm. Thus, when a sound wave enters the opening of the substrate, the sound wave pressure forces the outer diaphragm to displace and to carry the inner diaphragm to move, and the inner diaphragm itself will also be forced by the sound wave pressure to have a larger displacement than the outer diaphragm, enhancing the sensitivity. Further, using the inner and outer diaphragms to respond to different sound wave pressures can enhance the sound wave pressure sensing range.

Abstract: Described herein is a MEMS acoustic transducer device provided with a micromechanical detection structure that detects acoustic-pressure waves and supplies a transduced electrical quantity, and with an integrated circuit operatively coupled to the micromechanical detection structure and having a reading module that generates at output an audio signal as a function of the transduced electrical quantity. The integrated circuit is further provided with a recognition module, which recognizes a of sound activity event associated to the transduced electrical quantity. The MEMS acoustic transducer has an output that supplies at output a data signal that carries information regarding recognition of the sound activity event.

Abstract: A method for producing a MEMS device having improved charge elimination characteristics includes providing a substrate having one or more layers, and applying a first charge elimination layer onto at least one portion of one given layer of the substrate. The method may then (1) apply a sacrificial layer onto the first charge elimination layer, (2) apply a second charge elimination layer onto at least a portion of the sacrificial layer, and (3) deposit a movable layer onto at least a portion of the second charge elimination layer. To form a structure within the movable layer the method may etch the movable layer. The method may then etch the sacrificial layer to release the structure.

Abstract: An electrostatic loudspeaker comprises a membrane structure and an electrode structure. The membrane structure comprises a central membrane portion and a circumferential membrane portion. The electrode structure is configured to electrostatically interact with the membrane structure for causing a movement of the membrane structure along an axis of movement. The electrode structure comprises a circumferential electrode portion and an opening, the circumferential electrode portion being substantially aligned to the circumferential membrane portion and the opening being substantially aligned to the central membrane portion with respect to a direction parallel to the axis of movement. In an end position of the movement of the membrane structure, the central membrane portion is configured to extend at least partially through the opening. A method for operating an electrostatic loudspeaker and a method for manufacturing an electrostatic loudspeaker are also described.

Abstract: A condenser microphone includes a unit case that supports a condenser microphone unit, has an internal space in communication with a rear acoustic terminal of the microphone unit, and has an opening in a peripheral wall in communication with the internal space; a volume restrictor that reduces the volume of the internal space by partitioning the internal space; a circuit board disposed in the internal space and surrounded by the volume restrictor; and a rigid conductor that electrically connects a signal output terminal of the microphone unit and the circuit board. The circuit board intersects the center axis of the unit case. The rigid conductor is supported such that the rigid conductor slides along the volume restrictor. An elastic conductor is compressed between the rigid conductor and the circuit board or between the rigid conductor and the signal output terminal of the microphone unit.

Abstract: A microelectromechanical system (MEMS) microphone includes a base having a port extending there through. A MEMS die is coupled to the base, and the MEMS die includes a diaphragm and a back plate. An application specific integrated circuit (ASIC) is coupled to the base and the MEMS die. A cover is coupled to the base, and the cover includes customer pads. The customer pads on the cover are connected electrically to the ASIC, and the cover is arranged to form an air tight seal with the base and enclose the MEMS die and the ASIC. The microphone is connected to a customer board at the cover and arranged such that sound enters through the port in the base.

Abstract: A condenser microphone that provides a balanced output of audio signals from initial steps of a diaphragm and a fixed electrode is provided. The condenser microphone includes: a condenser microphone unit including a diaphragm being arranged opposite a fixed electrode; a first impedance converter being connected to the fixed electrode of the condenser microphone unit and outputting a first electric signal generated in the fixed electrode; and a second impedance converter being connected to the diaphragm of the condenser microphone unit and outputting a second electric signal generated in the diaphragm. By this structure, balanced outputs of the audio signals having phases reverse to each other are provided by the first and second impedance converters immediately after the condenser microphone unit.

Abstract: A capacitance sensor has a substrate, a vibration electrode plate formed over an upper side of the substrate, a back plate formed over the upper side of the substrate to cover the vibration electrode plate, and a fixed electrode plate arranged on the back plate facing the vibration electrode plate. At least one of the vibration electrode plate and the fixed electrode plate is divided into a plurality of regions. A sensing unit configured by the vibration electrode plate and the fixed electrode plate is formed in each of the divided regions. The plurality of sensing units output a plurality of signals having different sensitivities. At least some sensing units of the sensing units have vibration electrode plates having areas different from the areas of the vibration electrode plates in the other sensing units.

Abstract: A processing chip for a digital microphone and related input circuit and a digital microphone are described herein. In one aspect, the input circuit for a processing chip of a digital microphone includes: a PMOS transistor, a resistor, a current source, and a low-pass filter. The described processing chip possesses high anti high-frequency interference capabilities and the described input circuit possesses high high-frequency power supply rejection ratio.

Abstract: The present invention has: a condenser microphone unit which performs electroacoustic conversion according to a change in an electrostatic capacitance between a diaphragm and a fixed pole; a non-inverting amplifier which is connected to one of the diaphragm and the fixed pole, and which has an impedance converter which converts an output impedance of the microphone unit into a low impedance; an inverting amplifier which receives an input of an output signal of the non-inverting amplifier through an input resistance, and which has a feedback resistance; and a variable resistor which is connected between an output of the non-inverting amplifier and an output of the inverting amplifier, and in which a wiper is connected to the diaphragm or the fixed pole, whichever is not connected to the non-inverting amplifier, and the sensitivity changes according to the position of the wiper of the variable resistor.

Abstract: In an electrodynamic acoustic transducer which uses a surface potential of an electret dielectric film as a polarization voltage, prevention of partial suctional adhesion of a diaphragm caused by variation in surface potential across the electret dielectric film is ensured in a simple way. In an electrodynamic acoustic transducer including a diaphragm and a fixed pole which are arranged with a predetermined interval so as to face each other, a facing surface of either one of the diaphragm and the fixed pole having an electret dielectric film, a surface of the electret dielectric film is divided into a plurality of segment regions, and a predetermined surface potential is given to each of the segment regions by a polarization processing unit.

Abstract: A MEMS structure includes a backplate, a membrane, and an adjustable ventilation opening configured to reduce a pressure difference between a first space contacting the membrane and a second space contacting an opposite side of the membrane. The adjustable ventilation opening is passively actuated as a function of the pressure difference between the first space and the second space.

Abstract: A microphone package is described that includes a plastic lid, a substrate base, and two electrical components. The plastic lid includes a first conductive lid trace and the substrate base includes a first conductive substrate trace. The plastic lid is sealably coupled to the substrate base to form a sealed cavity. The substrate trace and the lid trace are arranged such that, when the cavity is sealed, an electrical connection is formed between the substrate trace and the lid trace. The first component is mounted on the substrate base and electrically coupled to the substrate trace. The second component is mounted on the lid and is electrically coupled to the lid trace. The electrical connection between the substrate trace and the lid trace provides electrical coupling between the first component and the second component. At least one of the first component and the second component includes a MEMS microphone die.

Abstract: A MEMS microphone has a base, a backplate, and a backplate spring suspending the backplate from the base. The microphone also has a diaphragm forming a variable capacitor with the backplate.

Abstract: A Microelectromechanical System (MEMS) microphone includes a printed circuit board, a MEMS die, and an integrated circuit. The MEMS die is disposed on a top surface of the printed circuit board. The integrated circuit is disposed at least partially within the printed circuit board and produces at least one output signal. The output signals of the integrated circuit are routed directly into at least one conductor to access pads at the printed circuit board and the access pads are disposed on a bottom surface of the printed circuit board that is opposite the top surface.

Abstract: A vacuum sealed directional microphone and methods for fabricating said vacuum sealed directional microphone. A vacuum sealed directional microphone includes a rocking structure coupled to two vacuum sealed diaphragms which are responsible for collecting incoming sound and deforming under sound pressure. The rocking structure's resistance to bending aids in reducing the deflection of each diaphragm under large atmospheric pressure. Furthermore, the rocking structure exhibits little resistance about its pivot thereby enabling it to freely rotate in response to small pressure gradients characteristic of sound. The backside cavities of such a device can be fabricated without the use of the deep reactive ion etch step thereby allowing such a microphone to be fabricated with a CMOS compatible process.

Abstract: A capacitance-type transducer has a substrate having a cavity, a vibrating electrode plate disposed above the substrate, a back plate disposed on the substrate, a fixed electrode plate disposed on the back plate opposite the vibrating electrode plate, a plurality of holes formed in the back plate and the fixed electrode plate, and a protrusion disposed on the back plate at a location opposing the vibrating electrode plate. In a view from a direction perpendicular to an upper surface of the substrate, a shortest distance from a cross-sectional center of the protrusion to an edge of a hole adjacent to the protrusion is larger than a shortest distance from a center of a region that is surrounded by the holes but not provided with the protrusion to an edge of a hole in the periphery.

Abstract: A MEMS structure and a method for operation a MEMS structure are disclosed. In accordance with an embodiment of the present invention, a MEMS structure comprises a substrate, a backplate, and a membrane comprising a first region and a second region, wherein the first region is configured to sense a signal and the second region is configured to adjust a threshold frequency from a first value to a second value, and wherein the backplate and the membrane are mechanically connected to the substrate.

Abstract: An electrostatic loudspeaker includes: a first electrode having acoustic transmission property; a second electrode having acoustic transmission property, and disposed so as to be opposed to the first electrode; a vibrating member having conductibility, and disposed between the first electrode and the second electrode; a first elastic member having elasticity, insulation property, and acoustic transmission property, and disposed between the vibrating member and the first electrode; a second elastic member having elasticity, insulation property, and acoustic transmission property, and disposed between the vibrating member and the second electrode; and a first separation member having insulation property and acoustic transmission property, and disposed on an opposite side of a face of the first electrode, which is opposed to the first elastic member.

Abstract: A silicon based capacitive microphone includes a printed circuit board, a shell mounted on the printed circuit board and forming a receiving space together with the printed board, a chamber support located on top of the printed circuit board and received in the receiving space, a transducer unit and a controlling chip respectively mounted on the chamber support, wherein the chamber support forms a first chamber together with the printed board, the chamber support includes an opening, the transducer unit is provided with a second chamber and covers the opening, the second chamber communicates with the first chamber via the opening.

Abstract: Provided is an acoustic sensor capable of improving an S/N ratio of a sensor without preventing reduction in size of the sensor. A diaphragm 43 as a movable electrode plate is formed on the top surface of a silicon substrate 42. The diaphragm 43 has a rectangular form, and four corners and midsections of long sides of the diaphragm 43 are supported by anchors 46. A displacement of the diaphragm 43 is minimal on a line D that connects between the anchors 46 at the midsections of the long sides. A displacement maximal point G, at which a displacement is maximal, is present on each side of the line D, and the line D extends in a direction intersecting with a line connecting between the displacement maximal points G.

Abstract: An implementation for an electret in a capacitive MEMS element including a pressure-sensitive diaphragm, which is produce-able using standard methods of semiconductor technology for easy integration into the manufacturing process of MEMS semiconductor elements. Such MEMS elements include at least one pressure-sensitive diaphragm including at least one deflectable diaphragm electrode of a capacitor system for signal detection and one fixed non-pressure-sensitive counter-element including at least one counter-electrode of this capacitor system, at least one electrode of the capacitor system being provided with an electrically charged electret, so that there is a potential difference between the two electrodes of the capacitor system. The electret includes at least two adjacent layers made from different dielectric materials, electrical charges being stored on their boundary surface.

Abstract: The invention is directed to echo cancellation for a microphone system. An exemplary microphone system comprises a first transistor, wherein a gate terminal of the first transistor is connected to a ground terminal via a microphone electret element, the microphone electret element being associated with a capacitance and a voltage, the microphone electret element reverse biasing the first transistor; and a second transistor in parallel with the first transistor, wherein a gate terminal of the second transistor is connected to the ground terminal via a capacitor, the capacitance of the capacitor being selected to suppress at least a portion of a common mode signal, and wherein the gate terminal of the second transistor is not connected to the microphone electret element. The common mode signal comprises the echo, which may be the output of a speaker system that is received as input to the microphone system.

Abstract: A method for driving a condenser microphone is provided. The condenser microphone comprises a membrane and an electrode constituting a capacity. A polarization voltage is applied between the membrane and the electrode. According to the method, an electrical signal generated by the condenser microphone based on a received acoustic signal causing a deflection of the membrane) is detected, and the polarization voltage is varied in response to the detected electrical signal.

Abstract: A micro-electro-mechanical microphone and manufacturing method thereof are provided. The micro-electro-mechanical microphone includes a diaphragm, which is formed on a surface of one side of a semiconductor substrate, exposed to the outside surroundings, and can vibrate freely under the pressure generated by sound waves; an electrode plate with air holes, which is under the diaphragm; an isolation structure for fixing the diaphragm and the electrode plate; an air gap cavity between the diaphragm and the electrode plate, and a back cavity under the electrode plate and in the semiconductor substrate; and a second cavity formed on the surface of the same side of the semiconductor substrate and in an open manner The air gap cavity is connected with the back cavity through the air holes of the electrode plate The back cavity is connected with the second cavity through an air groove formed in the semiconductor substrate.

Abstract: A MEMS microphone has 1) a backplate with a backplate interior surface and a plurality of through-holes, and 2) a diaphragm spaced from the backplate. The diaphragm is movably coupled with the backplate to form a variable capacitor. At least two of the through-holes have an inner dimensional shape (on the backplate interior surface) with a plurality of convex portions and a plurality of concave portions.

Abstract: A MEMS microphone. The MEMS microphone includes a substrate, a transducer support that includes or supports a transducer, a housing, and an acoustic channel. The transducer support resides on the substrate. The housing surrounds the transducer support and includes an acoustic aperture. The acoustic channel couples the acoustic aperture to the transducer, and isolates the transducer from an interior area of the MEMS microphone.

Abstract: A MEMS acoustic transducer provided with a substrate having cavity, and a membrane suspended above the cavity and fixed peripherally to the substrate, with the possibility of oscillation, through at least one membrane anchorage. The membrane comprises at least one spring arranged in the proximity of the anchorage and facing it, and is designed to act in tension or compression in a direction lying in the same plane as said membrane.

Abstract: In accordance with an embodiment of the present invention, a micro-electro-mechanical system (MEMS) device includes a first plate, a second plate disposed over the first plate, and a first moveable plate disposed between the first plate and the second plate. The MEMS device further includes a second moveable plate disposed between the first moveable plate and the second plate.

Abstract: A microphone includes a diaphragm assembly supported by a substrate. The diaphragm assembly includes at least one carrier, a diaphragm, and at least one spring coupling the diaphragm to the at least one carrier such that the diaphragm is spaced from the at least one carrier. An insulator (or separate insulators) between the substrate and the at least one carrier electrically isolates the diaphragm and the substrate.

Abstract: The invention relates to a moving part for an electro-dynamic transducer, including at least one mandrel supporting a winding of at least one coiled wire. The mandrel includes at least one first element rigidly connected inside at least one second element for guiding the moving part inside the transducer. The first element has a winding support for the coiled wire so that the coil is located inside the mandrel, as well as vibration transmitter, such as a diaphragm, the vibration being generated by the movement of the coil induced by the flow of current in the coil wire. The invention also relates to an electro-dynamic transducer including such a moving part.

Abstract: A MEMS device includes substrate having a cavity. A dielectric layer is disposed on a second side of substrate at periphery of the cavity. A backplate structure is formed with the dielectric layer on a first side of the substrate and exposed by the cavity. The backplate structure includes at least a first backplate and a second backplate. The first backplate and the second backplate are electric disconnected and have venting holes to connect the cavity and the chamber. A diaphragm is disposed above the backplate structure by a distance, so as to form a chamber between the backplate structure and the diaphragm. A periphery of the diaphragm is embedded in the dielectric layer. The diaphragm serves as a common electrode. The first backplate and the second backplate respectively serve as a first electrode unit and a second electrode unit in conjugation with the diaphragm to form separate two capacitors.

Abstract: Measures for dynamically regulating the microphone sensitivity of a MEMS microphone component at low frequencies by way of variable roll-off behavior are proposed. The micromechanical microphone structure of the component, which is implemented in a layer structure on a semiconductor substrate, encompasses an acoustically active diaphragm having leakage openings which spans a sound opening in the substrate back side, and a stationary acoustically permeable counterelement having through openings which is disposed in the layer structure above/below the diaphragm. The component furthermore encompasses a capacitor assemblage for signal sensing, having at least one deflectable electrode on the diaphragm and at least one stationary electrode on the counterelement, and an arrangement for implementing a relative motion between the diaphragm and counterelement parallel to the layer planes.

Abstract: An electronic device comprising a substrate, a cover delimiting at least a part of a main surface of the substrate to thereby form a cover-substrate arrangement enclosing a hollow space and having a through hole, an electroacoustic transducer configured for converting between an electric signal and an acoustic signal and being mounted on the substrate acoustically coupled with the hollow space in such a way that the hollow space constitutes a back volume of the electroacoustic transducer, wherein the electroacoustic transducer provides an acoustical coupling between the hollow space and an exterior of the cover-substrate arrangement via the through hole, an electronic chip mounted within the cover-substrate arrangement and electrically coupled with the electroacoustic transducer for communicating electric signals between the electronic chip and the electroacoustic transducer, and at least one electronic member mounted on the substrate within the cover-substrate arrangement and configured for providing an elec

Abstract: A handheld condenser microphone is provided with a condenser microphone unit having two unidirectional condenser elements. A conductive fabric 221 is put between a lock ring 213 and the second condenser element 10b, when an acoustic-electric transducer 220 is fixed inside a unit case 210 by fastening force of the lock ring 213.

Abstract: MEMS devices with a rigid backplate and a method of making a MEMS device with a rigid backplate are disclosed. In one embodiment, a device includes a substrate and a backplate supported by the substrate. The backplate includes elongated protrusions.

Abstract: A MEMS microphone. The MEMS microphone includes a back plate, a membrane, a support structure, a substrate, and an overtravel stop. The membrane is coupled to the back plate. The support structure includes a support structure opening and a first side of the support structure is coupled to a second side of the back plate. The substrate includes a substrate opening and a first side of the substrate is coupled to a second side of the support structure. The overtravel stop limits a movement of the membrane away from the back plate and includes at least one of an overtravel stop structure coupled to the substrate, an overtravel stop structure formed as part of a carrier chip, and an overtravel stop structure formed as part of the support structure in the support structure opening.

Abstract: A MEMS device, such as a microphone, uses a fixed perforated plate. The fixed plate comprises an array of holes across the plate area. At least a set of the holes adjacent the outer periphery comprises a plurality of rows of elongate holes, the rows at different distances from the periphery. This design improves the mechanical robustness of the membrane and can additionally allow tuning of the mechanical behavior of the plate.

Abstract: A MEMS inertial sensor and a method for manufacturing the same are provided. The method includes: depositing a first carbon layer on a semiconductor substrate; patterning the first carbon layer to form a fixed anchor bolt, an inertial anchor bolt and a bottom sealing ring; forming a contact plug in the fixed anchor bolt and a contact plug in the inertial anchor bolt; forming a first fixed electrode, an inertial electrode and a connection electrode on the first carbon layer, where the first fixed electrode and the inertial electrode constitute a capacitor; forming a second carbon layer on the first fixed electrode and the inertial electrode; and forming a sealing cap layer on the second carbon layer and the top sealing ring. Under an inertial force, only the inertial electrode may move, the fixed electrode will almost not move or vibrate, which improves the accuracy of the MEMS inertial sensor.

Abstract: A MEMS device, such as a microphone, uses a perforated plate. The plate comprises an array of holes across the plate area. The plate has an area formed as a grid of polygonal cells, wherein each cell comprises a line of material following a path around the polygon thereby defining an opening in the center. In one aspect, the line of material forms a path along each side of the polygon which forms a track which extends at least once inwardly from the polygon perimeter towards the center of the polygon and back outwardly to the polygon perimeter. This defines a meandering hexagon side wall, which functions as a local spring suspension.

Abstract: A method of fabricating an integrated semiconductor device, comprising: providing a substrate having a first region and a second region; and forming a semiconductor unit on the first region and forming a micro electro mechanical system (MEMS) unit on the second region in one process.

Abstract: A method of fabricating a micro-electrical-mechanical system (MEMS) transducer comprises the steps of forming a membrane on a substrate, and forming a back-volume in the substrate. The step of forming a back-volume in the substrate comprises the steps of forming a first back-volume portion and a second back-volume portion, the first back-volume portion being separated from the second back-volume portion by a step in a sidewall of the back-volume. The cross-sectional area of the second back-volume portion can be made greater than the cross-sectional area of the membrane, thereby enabling the back-volume to be increased without being constrained by the cross-sectional area of the membrane. The back-volume may comprise a third back-volume portion. The third back-volume portion enables the effective diameter of the membrane to be formed more accurately.

Abstract: A microphone assembly comprising includes a base, at least one side wall, and a cover. The side wall is disposed on the base. The cover is coupled to the at least one side wall. The base, the side wall, and the cover form a cavity and the cavity has a MEMS device disposed therein. A top port extends through the cover and a first channel extends through the side wall. The first channel is arranged so as to communicate with the top port. A bottom port extends through the base. The MEMS device is disposed over the bottom port. A second channel is formed and extends along a bottom surface of the base. The second channel extends between and communicates with the first channel and the bottom port. Sound received by the top port is received at the MEMS device.

Abstract: A condenser microphone includes multiple condenser microphone units. Each unit includes an impedance converter. The condenser microphone units are connected in series such that outputs of the impedance converter in one of the condenser microphone units drive another of the condenser microphone units. A polarization voltage is accumulated to a DC voltage supplied from a DC voltage supply through a voltage adjuster to be applied to one of a diaphragm and a fixed electrode, and a voltage applied to the one of the diaphragm and the fixed electrode is adjusted by the voltage adjuster.