[go: up one dir, main page]

WO1994006002A1 - Capteur capacitif et procede de mesure des variations de la capacite - Google Patents

Capteur capacitif et procede de mesure des variations de la capacite Download PDF

Info

Publication number
WO1994006002A1
WO1994006002A1 PCT/US1993/008352 US9308352W WO9406002A1 WO 1994006002 A1 WO1994006002 A1 WO 1994006002A1 US 9308352 W US9308352 W US 9308352W WO 9406002 A1 WO9406002 A1 WO 9406002A1
Authority
WO
WIPO (PCT)
Prior art keywords
capacitor
voltage
generating
output signal
series
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1993/008352
Other languages
English (en)
Inventor
Robert Wayne Paglione
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sarnoff Corp
Original Assignee
David Sarnoff Research Center Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by David Sarnoff Research Center Inc filed Critical David Sarnoff Research Center Inc
Publication of WO1994006002A1 publication Critical patent/WO1994006002A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2605—Measuring capacitance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/24—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance
    • G01D5/2405—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance by varying dielectric
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • G01N27/228—Circuits therefor

Definitions

  • CAPACITANCE The invention relates to an apparatus and method for measuring the capacitance of a capacitive sensor and, more particularly, to the measurement of variations in the capacitance of the sensor.
  • Measuring circuitry such as that disclosed by Moser can be realized using a microprocessor to switch in various combinations of capacitors for the variable capacitor while balancing the bridge.
  • a look-up table in the microprocessor then provides an output code for the voltage corresponding to the value of the measured capacitance.
  • This type of circuit is difficult to reduce to a single monolithic integrated circuit due to the large values and number of capacitors used and requires extra components to produce a linear electrical output with change in dimension or distance traveled.
  • the invention is an apparatus for measuring the capacitance of a capacitive sensor comprising means for charging the capacitor; means for generating an electrical signal when the capacitor is charged to a certain voltage; and means for generating an output signal corresponding to the time required to charge the capacitor to the certain voltage.
  • the invention is also a method of measuring the capacitance of a capacitor comprising the steps of charging the capacitor; measuring the time required to charge the capacitor to a first voltage; and generating an output signal linearly proportional to the time required to charge the capacitor to the first voltage.
  • Figs. 1(a) and Kb) are cross-sectional views of a capacitive sensor including a sensor body and electronics.
  • Figs. 2 is a cross-sectional view of another sensor body.
  • Figs. 3(a) and 3(b) are cross-sectional views of another sensor body.
  • Figs. 4 is a cross-sectional view of another sensor body.
  • Fig. 5 is a block diagram of an electrical circuit for measuring capacitance.
  • Figs. 6 is a detailed circuit diagrams of an embodiment of the electrical circuit of Fig. 5.
  • Fig. 7 is a timing diagram for the operation of the electrical circuit of Fig. 5.
  • Figs. 8 is a block diagram of another electrical circuit for measuring capacitance.
  • a capacitive sensor of the invention comprises a sensor body
  • the sensor body 10 comprises a piston 12 with a dielectric sleeve 14 mounted thereon, a body 16, and a cylindrical opening 18 extending a distance into the body 16 from an end thereof.
  • the inner and outer walls of the cylindrical opening 18 are covered with electrically conductive layers 20 and 22, respectively, which form the electrodes of a capacitor .
  • the electrically conductive layers 20 and 22 are connected to the external electrodes 24 and 26 respectively.
  • the electrodes 24 and 26 are connected to the input terminals of the electronics 10.
  • the dielectric 14 moves in and out of the opening 18 thereby changing the value of the capacitor.
  • the electronics 10 measure the capacitance and produce an output voltage or pulse-width-modulated signal which is preferably linearly proportional to the value of capacitance. The measurement of the change in the capacitance provides a direct measure of the distance moved by the piston 12.
  • the body 16 is typically a cylinder preferably formed of a material such as Kapton or Mylar with screened-on conductors as the layers 20 and 22. Plated plastic parts of any suitable shape could be used.
  • the electrodes of the sensor capacitor are fixed and an insulating dielectric attached to the moving member moves in and out of the fixed capacitor to effect the capacitance change.
  • a sensor body 30 includes an electrically conductive layer, corresponding to the layer 22 of Fig. 1, which is divided into three separate, unconnected conductive layers 32, 34 and 36.
  • the conductive layers 32, 34 and 36 together with the electrically conductive layer 20 form the capacitor electrodes of three separate capacitors.
  • the electrically conductive layers 32, 34 and 36 are connected to the external electrodes 38, 40 and 42 respectively.
  • the first capacitor formed by layers 20 and 32, is always filled with the dielectric body 14 regardless of the position of the piston 12, thus providing a reference capacitor which can be used to measure, and correct for, wear, temperature variations and other effects which might change the characteristics of the dielectric and, thus, the magnitude of the capacitor.
  • the second capacitor formed by layers 20 and 34, corresponds to the capacitor of Fig. 1.
  • the extent to which the body 14- fills the space between the layers 20 and 34 varies, thereby changing the value of the capacitor.
  • the measurement of the change in the capacitance of this capacitor provides a direct measure of the distance moved by the piston 12.
  • the third capacitor formed by layers 20 and 36, has any other material present in the sensor, for example an oil such as is used in a shock absorber, between the electrodes.
  • the third capacitor since it" is always filled with the other material regardless of the position of the piston 12, provides a reference capacitor which can be used to measure, and correct for the change in the characteristics of such material and, thus, the magnitude of the capacitor.
  • a sensor body 50 containing a variable capacitor comprises a piston 52 with a dielectric slab 54 mounted thereon, a body 56, and a rectangular opening 57 extending a distance into the body 56 from an end thereof. Two opposed walls of the opening 57 are covered with electrically conductive layers 58 and 60, respectively, which form the electrodes of a capacitor.
  • the electrically conductive layers.58 and 60 are connected to the first external electrode 68 and common electrode 70 respectively.
  • the dielectric body 54 moves in and out of the opening 57 thereby changing the value of the capacitor.
  • the measurement of the change in the capacitance of this capacitor provides a direct measure of the distance moved by the piston 52.
  • the sensor body 50 also includes second and third reference capacitors to provide calibration of the sensor body due to changes in the characteristics of the variable capacitor due to wear, temperature variations and other effects which might change the characteristics of the dielectric and, thus, the magnitude of the capacitor or the characteristics of other materials such as an oil present in the sensor between the electrodes.
  • the second capacitor comprises a dielectric body 62 of the same material as the body 54 between electrically conducting layers 64 and 66 which are connected to the common electrode 70 and the second external electrode 72, respectively.
  • the third capacitor comprises a material 74, such as an oil, between electrically conducting layers 76 and 78 which are connected to the common electrode 70 and the third external electrode 80, respectively.
  • an alternative sensor body 100 comprises a piston 102, an outer metal cylinder 104 with a dielectric sleeve 106 therebetween.
  • the magnitude C of the capacitor is:
  • the sensor body was made using telescoping brass tubing as the electrodes and heatshrink fluorinated ethylene propylene (FEP) as the insulator.
  • FEP heatshrink fluorinated ethylene propylene
  • the maximum capacitance C is then equal to about 130 picofarads.
  • the invention comprises charging a capacitor from a constant current source.
  • the capacitor charges at a uniform, linear rate and thus the voltage across the capacitor increases linearly during charging.
  • the capacitor can be charged from a current or voltage source in a substantially linear way. In this case, the voltage V developed across the capacitor C as a function of time T is
  • V V 0 (l-e-(T/RO).
  • V Q is the asymptotic value of the voltage across the capacitor and R is the resistance across the capacitor.
  • R is the resistance across the capacitor.
  • the capacitance is thus linearly proportional to the length of time required to charge the capacitor to a voltage V provided that T «RC.
  • the invention further comprises comparing the voltage developed across the capacitor to a reference voltage and generating a signal pulse once the voltage across the capacitor has reached a certain level.
  • the invention further comprises measuring the time required to charge the capacitor, using for example counting means, and generating an output signal linearly proportional to the charging time T.
  • the signal pulse resets the counter and latches the latch.
  • the output of the latch in digital form can be used in apparatus (not shown) which accepts a digital signal. Alternatively the output of the latch can be converted to an analog signal.
  • a preferred circuit 150 for measuring the change in capacitance is shown in Fig. 5 in block diagram form.
  • a constant-current source 152 having an input electrode 154 connected to a power source such as a battery charges a variable capacitor 156 through a multiplexer 158.
  • the multiplexer alternately connects the current source 152 to the electrode of the capacitor 156 and to a source of reference potential such as ground potential.
  • the voltage V developed across the capacitor 156 is a linear ramp from 0 V with the slope of the ramp being proportional to the value of the sensor capacitance.
  • the voltage V is also applied to a first input electrode 160 of a comparator 162.
  • the comparator 162 changes output state when the voltage V c becomes greater than a reference voltage V re f applied to a second comparator input electrode 164.
  • the clock oscillator 174 provides two synchronous outputs, a first series of high frequency pulses 176 and a second series of low frequency pulses 178.
  • the first series 174 is counted by the counter 166 to provide the measure of time; the second series 178 switches the multiplexer 158, alternately connecting the the input electrode of the variable capacitor 156 to the current source or to ground.
  • the period of the second series must be long compared to the time T required to charge the capacitor 154.
  • a DAC 170 converts the digital representation of the counts into a voltage at electrode 172.
  • DAC 170 is not required if the device connected to electrode 172 accepts a signal in digital format.
  • Fig. 6 a detailed implementation of the circuit of Fig. 5 is shown. In the Figure all resistors are in kilohms and all capacitors are in microfarads ( ⁇ f) unless otherwise indicated.
  • the circuit includes a constant-current source 152 including transistor 153, a variable capacitor 156, multiplexer 158, comparator 162, level converter 163, counter 166, latch 168, DAC 170, output section 210 and power supply 200.
  • the clock 174 provides two synchronous outputs. The high-frequency output is counted by the counter; the low-frequency output switches the multiplexer 158.
  • the multiplexer 158 alternately connects the capacitor 156 to the current source or to ground.
  • Transistor 153 is preferably a type 2N4250.
  • Multiplexer 158 is preferably a type 74HC4053.
  • Comparator 162 is preferably a type CA339.
  • Level converter 163 is a Schmidt trigger used to sharpen the pulse output generated by the comparator 162.
  • Converter 163 is preferably a type CD4093. The output pulse from converter 163 resets counters 166 and latches the data of latches 168.
  • Output section 210 including an operational amplifier 212, provides means for adjusting the voltage swing of the analog output.
  • Latch 168 includes two octal latch circuits 168A which are preferably type 74HC564.
  • Counters 166 include counter circuits 166A each of which is one half of an eight bit binary upcounter which are preferably type 74HC4520, NAND gates 166B which are preferably type 74HC20 and quad two input OR gates 166C which are preferably type 74HC32.
  • the NAND gates 168B and the OR gates 168C are connected to the counter circuits 168A as shown to produce a 14-bit binary counter.
  • DAC 170 includes the converter circuit 170A which is preferably a Burr-Brown 12 bit digital-to- analog converter type DAC80-CBI-V.
  • Clock 174 is preferably a type 74HC4060 having a clock frequency of about 11 MHz.
  • the divided clock frequency used to control multiplexer 158 is about 700 Hz.
  • the parts can be purchased from one of Harris Corporation, Motorola, Inc. or Signetics
  • Operational amplifier 212 is preferably a Bun- Brown type CA3140.
  • Power supply 200 is a conventional three terminal regulator, producing +12V, -12V and +5V outputs.
  • the positive polarity section includes a type 1N5001 diode 202, 0.1 ⁇ f capacitor to ground, a type 7812 12 V regulator 204, 0.1 ⁇ f filtering capacitor to ground and a type 7905 5V regulator 206.
  • the negative polarity section includes a type 1N5001 diode 202, 0.1 ⁇ f capacitor to ground, a type 7912 -12 V regulator 208 and 0.1 ⁇ f filtering capacitor to ground.
  • a timing diagram for the operation of the circuits of Figs. 5 and 6 is shown in Fig. 7. In Fig.
  • the voltage Vc increases linearly with time T during the time interval TAB during which the multiplexer 158 connects the constant current source 152 to the capacitor 156.
  • the time interval Tc is the alternating time interval where the multiplexer 158 connects the constant current source 152 to the reference potential.
  • TAB is approximately equal to Tc and their sum is equal to the period of the low- frequency output of the clock 174.
  • the time for the capacitor to charge to voltage Vref is TO ⁇ TAB.
  • comparator 162 changes state, emitting a reset pulse which stops the counter 166 counting and causes it to reset. This is shown schematically in Fig. 7(b), where, during time interval A, counter 166 is counting. During time interval B, counter 166 is not counting.
  • the counter After the first cycle with the circuit of Fig. 6, the counter begins counting at the start of interval C and continues to count until the comparator changes state at the end of the next interval A.
  • the low-frequency clock pulse is OR'd (for example, using one- quarter of a 74HC32A quad 2-input OR gate) with the comparator output, and this OR'd output is used as the counter reset and latch enable, then the counter will only be counting during the voltage ramp of Vc.
  • the clock pulse can be used to prevent the counter from counting during the interval C when the capacitor is being discharged.
  • an alternative embodiment of the circuit includes a microprocessor 802 which replaces the counter, clock, and latch. By using a pulse-width-modulated output port, it can also emulate the DAC, if required.
  • a suitable microprocessor is an Intel model 87C51FA.
  • Fig. 8 the use of a reference capacitor 804 to compensate for environmental changes in the value of the capacitor 156 is shown.
  • the multiplexer provides alternate charge/discharge cycles for both the variable capacitor 156 and the reference capacitor 804.
  • the comparator 162 operates to generate a signal when the voltage across either capacitor exceeds V re f.
  • the microprocessor uses changes in the value of the reference capacitor 804 to correct the measurement of capacitor 156.
  • the invention is apparatus for measuring the variation in the capacitance of a capacitive sensor comprising means for charging the capacitor; means for generating an electrical signal when the capacitor is charged to a certain voltage; and means for generating an output signal corresponding to the time required to charge the capacitor to the certain voltage.
  • the means for charging the capacitor comprises means for providing a source of constant electrical current to an electrode of the capacitor and the means for generating an output signal comprises comparator means for comparing the voltage on the capacitor to a reference voltage.
  • the comparator means generates an output signal when the voltage on the capacitor is greater than the reference voltage.
  • the means for generating an output signal may comprise means for generating a first series of timing pulses; and means for counting the first series of pulses emitted by the generating means in a given time interval.
  • the multiplexing means alternately connects an electrode of the capacitor to the means for charging the capacitor and to a reference potential.
  • the means for generating an output signal corresponding to the time required to charge the capacitor can be implemented using a microprocessor
  • the invention is also a position sensing device having variable extension comprising capacitor means variable with extension of the device; constant current means for charging the capacitor; and means for forming an electrical output signal representative of the extension of the device. Also a method of measuring the capacitance of a capacitor comprising the steps of charging the capacitor from a constant current source; comparing the voltage developed across the capacitor to a reference voltage; generating a signal pulse once the voltage across the capacitor has reached a certain level; measuring the time required to charge the capacitor, using for example counting means; and generating an output signal linearly proportional to the charging time.
  • the invention can be used as part of a position sensor or shock absorber to adjust the distance between a road surface and the chassis of a motor vehicle.
  • the output of the sensor of the invention may be connected to a computer for controlling the leveling of a vehicle.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Abstract

Appareil et procédé permettant la mesure de la capacité d'un condensateur ou de la capacité variable d'un capteur capacitif (10). Le condensateur est chargé par du courant provenant d'une source et le temps requis pour charger le condensateur jusqu'à un certain niveau de tension est mesuré. Un signal de sortie linéairement proportionnel au temps requis pour charger le condensateur jusqu'audit niveau de tension est produit. L'invention concerne également l'utilisation du capteur pour mesurer les variations de la longueur d'un dispositif télescopique (8) tel qu'un amortisseur.
PCT/US1993/008352 1992-09-10 1993-09-10 Capteur capacitif et procede de mesure des variations de la capacite Ceased WO1994006002A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US94308092A 1992-09-10 1992-09-10
US07/943,080 1992-09-10

Publications (1)

Publication Number Publication Date
WO1994006002A1 true WO1994006002A1 (fr) 1994-03-17

Family

ID=25479070

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1993/008352 Ceased WO1994006002A1 (fr) 1992-09-10 1993-09-10 Capteur capacitif et procede de mesure des variations de la capacite

Country Status (1)

Country Link
WO (1) WO1994006002A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5811807A (en) * 1996-07-19 1998-09-22 Ail Systems, Inc. Uncooled background limited detector and method
DE10258417B3 (de) * 2002-12-13 2004-08-12 Beru Ag Verfahren und Schaltungsanordnung zum Erfassen und/oder Bestimmen der Beschaffenheit eines Mediums
GB2425843A (en) * 2005-05-07 2006-11-08 Acam Messelectronic Gmbh Measuring a capacitance by measuring charging / discharging time
CN102129145A (zh) * 2010-01-12 2011-07-20 马克西姆综合产品公司 一种带有电容测量电路的微机电系统设备驱动器
US9218095B2 (en) 2013-05-21 2015-12-22 Synaptics Incorporated Non-linear feedback capacitance sensing
CN109405733A (zh) * 2018-12-14 2019-03-01 中核新科（天津） 精密机械制造有限公司 快速高精度平面平行度测量装置
CN110749779A (zh) * 2019-12-05 2020-02-04 上海芯凌微电子有限公司 电容式传感器电容变化检测方法及电路

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4149231A (en) * 1977-05-04 1979-04-10 Bunker Ramo Corporation Capacitance-to-voltage transformation circuit
US4404481A (en) * 1980-10-20 1983-09-13 Matsushita Electric Industrial Co., Ltd. Capacitance to voltage conversion apparatus
US4558274A (en) * 1983-09-14 1985-12-10 Johnson Service Company Apparatus and method determining the value of a capacitance
US4587850A (en) * 1983-09-24 1986-05-13 Boge Gmbh Arrangement for determining the travel of a piston
US4825147A (en) * 1988-09-14 1989-04-25 Sencore, Inc. Capacitance measuring method and apparatus
US4961055A (en) * 1989-01-04 1990-10-02 Vickers, Incorporated Linear capacitance displacement transducer

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4149231A (en) * 1977-05-04 1979-04-10 Bunker Ramo Corporation Capacitance-to-voltage transformation circuit
US4404481A (en) * 1980-10-20 1983-09-13 Matsushita Electric Industrial Co., Ltd. Capacitance to voltage conversion apparatus
US4558274A (en) * 1983-09-14 1985-12-10 Johnson Service Company Apparatus and method determining the value of a capacitance
US4587850A (en) * 1983-09-24 1986-05-13 Boge Gmbh Arrangement for determining the travel of a piston
US4825147A (en) * 1988-09-14 1989-04-25 Sencore, Inc. Capacitance measuring method and apparatus
US4961055A (en) * 1989-01-04 1990-10-02 Vickers, Incorporated Linear capacitance displacement transducer

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5811807A (en) * 1996-07-19 1998-09-22 Ail Systems, Inc. Uncooled background limited detector and method
US6166381A (en) * 1996-07-19 2000-12-26 Ail Systems, Inc. Uncooled background limited detector and method
DE10258417B3 (de) * 2002-12-13 2004-08-12 Beru Ag Verfahren und Schaltungsanordnung zum Erfassen und/oder Bestimmen der Beschaffenheit eines Mediums
GB2425843A (en) * 2005-05-07 2006-11-08 Acam Messelectronic Gmbh Measuring a capacitance by measuring charging / discharging time
US7403020B2 (en) 2005-05-07 2008-07-22 Acam-Messelectronic Gmbh Method and device for measuring capacitances
GB2425843B (en) * 2005-05-07 2008-10-15 Acam Messelectronic Gmbh Method and device for measuring capacitances
CN102129145A (zh) * 2010-01-12 2011-07-20 马克西姆综合产品公司 一种带有电容测量电路的微机电系统设备驱动器
US9218095B2 (en) 2013-05-21 2015-12-22 Synaptics Incorporated Non-linear feedback capacitance sensing
CN109405733A (zh) * 2018-12-14 2019-03-01 中核新科（天津） 精密机械制造有限公司 快速高精度平面平行度测量装置
CN109405733B (zh) * 2018-12-14 2024-04-09 中核新科（天津）精密机械制造有限公司 快速高精度平面平行度测量装置
CN110749779A (zh) * 2019-12-05 2020-02-04 上海芯凌微电子有限公司 电容式传感器电容变化检测方法及电路

Similar Documents

Publication Publication Date Title
US5585733A (en) Capacitive sensor and method of measuring changes in capacitance
US6700392B2 (en) Digital measurement circuit and system using a grounded capacitive sensor
KR101667978B1 (ko) 아날로그 디지털 컨버터의 내부 커패시터와 기준 전압을 이용한 정전용량형 터치 센싱
US6307385B1 (en) Capacitance measuring circuit for a capacitive sensor
JPH0114545B2 (fr)
JPH08304488A (ja) デュアルコンデンサの容量値の変化を測定する方法及び装置
EP0397584B1 (fr) Appareil de mesure de l'humidité
HK1000259A1 (en) Humidity measuring apparatus
WO1994006002A1 (fr) Capteur capacitif et procede de mesure des variations de la capacite
JP2515456B2 (ja) センサ信号の処理装置
US5408236A (en) High-voltage unit comprising a measuring divider/resistor arrangement
JPH073340B2 (ja) センサ信号を処理する装置
KR20040053121A (ko) 센서 용량 검출 장치 및 센서 용량 검출 방법
US5406137A (en) Circuit arrangement for evaluating the signal of a capacitive measuring sensor
US4241317A (en) Frequency generator suitable for use as position-frequency transducer
US5189376A (en) Method for the measurment of capacitance, with application to linear measurement of distance
US5585559A (en) Environment measuring apparatus
JP2003057093A (ja) 液面レベル検出器用電極
JP3044938B2 (ja) 静電容量形変位センサ
CN112504519A (zh) 一种压力检测电路、装置及压力输入装置
KR19980085037A (ko) 액체 레벨 검출기
EP1072870B1 (fr) Détecteur capacitif pour mesure du niveau de l'eau dans un réservoir d'huile
SU1767451A1 (ru) Измерительный преобразователь с емкостным датчиком
SU1188523A1 (ru) Емкостной датчик перемещений
JP2732671B2 (ja) 熱検出方法並びに熱検出回路

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): CA JP KR

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB GR IE IT LU MC NL PT SE

DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
121 Ep: the epo has been informed by wipo that ep was designated in this application
122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: CA