CN100544195C

CN100544195C - Linear capacitance is measured and non-contact switch

Info

Publication number: CN100544195C
Application number: CNB2005800143131A
Authority: CN
Inventors: 李应流
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-08-16
Filing date: 2005-08-16
Publication date: 2009-09-23
Anticipated expiration: 2025-08-16
Also published as: CN1951003A

Abstract

A kind of capacitance measuring device that improves the sensitiveness and the accuracy of capacitive transducer, proximity transducer and non-contact switch.One end ground connection of each in measured two capacitors (C1, C2), and utilize negative feedback to keep essentially identical voltage potential by operational amplifier (A1) or a plurality of amplifier (A0, A1).This installs by periodically for example sine signal source (G1) or a plurality of signal source (G1, G2) driving, and comprises difference amplifier (A2), the signal of telecommunication that its appointment arithmetic function that is used for the electric capacity of generation and two capacitors (C1, C2) has linear relationship.Utilize this capacitance measuring device to realize non-contact switch.This non-contact switch comprises two sensing electrodes (E1, E2) corresponding to tested two capacitors (C1, C2), and the front that has container shapes in one embodiment.

Description

Linear capacitance is measured and non-contact switch

The cross reference related application

The application requires the priority of following patent application: the name of submitting to June 15 in 2005 is called the U.S. Provisional Patent Application No.60/690 of LINEAR CAPACITANCE MEASUREMENT AND TOUCHLESS SWITCH, 486, the name of submitting on March 17th, 2005 is called the U.S. Provisional Patent Application No.60/662 of CAPACITANCE MEASUREMENT AND TOUCHLESS SWITCH, 378, the name of submitting on October 19th, 2004 is called the U.S. Provisional Patent Application No.60/619 of DIFFERENTIALCAPACITANCE MEASUREMENT AND TOUCHLESS SWITCH, the name of submitting on August 16th, 697 and 2004 is called the U.S. Provisional Patent Application No.60/601 of DI FFERENTIAL CAPACITANCE MEASUREMENT AND TOUCHLESS SWITCH, 610.

Statement N/A about federal sponsored research or exploitation

Background of invention

The present invention relates generally to capacitance measuring device and technology, and more specifically relate to adopt the capacitance measurement technology near detector (proximity detector), for example non-contact switch.

In recent years, more and more need better technology to operate publicly available facilities and equipment and do not need the surface of the manual active device of user's actual contact (for example contact-making switch).This facilities and equipment comprise elevator, automatic vending machine, secure access panel (securityaccess panels), information terminal or the like.Owing to do not need user's Body contact may be used other people's contact of these facilities or equipment and the switch that pollutes before, so can reduce bacterium and transmission of disease significantly.

For example, the user usually operates for example elevator of communal facility by the one or more switch of Body contact, and this switch may be before contacted by considerable people.Some of these philtrums may be from can making them be exposed to pollutant, for example potential harmful or communicable poisonous substance or pathogenic organisms, environment.When the required one or more switch of these person operating of contacts elevators, just exist these people pollutant is attached to the risk on switch surface, and these pollutants may keep survival there for a long time.These pollutants may be delivered to the elevator user of this switch of Body contact subsequently afterwards from switch, thereby may make user subsequently obtain disease or other serious uncomfortable situation.

During Asia outburst serious acute respiratory syndrome (SARS), many public members fear to use needs them to contact for example any urban operating mechanism of contact-making switch of manual active device.In order to alleviate the public's worry, carried out the program of these apparatus surfaces regularly being carried out cleaning and disinfection.This program generally is invalid, because what is better no matter these active device cleaning and disinfections get, they all may be polluted by user afterwards again.As a result, the manual active device of the facilities and equipment that can use from the public with hiding for example contact-making switch shift noxious pollutant to after user's still reduction of risk.

Now existing the employing not needing to realize the active device of user's Body contact apparatus surface based on electric capacity near detector.This near detector according to operating having different voltage potentials and the electric field that produces between two conductive bodies of physical separation each other and the principle of electric capacity.Electric capacity between two conductive bodies increases and increases along with body surface area usually, perhaps reduces along with the distance between the object and increases.

But, the tradition based on electric capacity near detector defectiveness when they are used to realize non-contact switch.For example, usually be difficult to adjust based on electric capacity near detector sensitivity guaranteeing using this non-contact switch to be started reliably by a large amount of users near detector, and require this switch to be not easy to be subjected to the influence of noise and/or environmental change simultaneously.This is owing to when realizing non-contact switch, and is less relatively based on the equivalent capacity near the required measurement of detector of electric capacity.

Particularly, when human body very near or near based on electric capacity near the sensing electrode of detector the time, be to be equal to the equivalent capacity of measuring two series capacitors near detector, as the stray capacitance between capacitance sensing circuit and circuit ground end of ignoring.One of series capacitor is formed between sensing electrode and the human body, and another capacitor is formed between human body and the ground.Capacitance between sensing electrode and human body depends mainly on the distance between them, and less is decided by the size and the feature of human body.For example, when human body is not very when the sensing electrode, in the capacitance between sensing electrode and the human body much smaller than the capacitance between human body and ground (ground).Therefore, utilizing the equivalent capacity that must measure based on the non-contact switch near the detector realization of electric capacity is the electric capacity of being measured by traditional contact-making switch much smaller than generally.

Fig. 1 illustrates the non-contact switch near detector 100 realized of utilization based on electric capacity, this comprise sensing electrode 112, capacitance sensing circuit 114 near detector 100 and be formed on finger and sensing electrode 112 between capacitor (C _A), the remainder of human body and the capacitor (C between the sensing electrode 112 _B), the capacitor (C between human body and the ground _C) and in this is analyzed the capacitor (C between negligible capacitance sensing circuit 114 and the ground _D) equivalent capacity.When finger during, can regard capacitor C between finger and sensing electrode 112 as at the electric capacity between human body and the sensing electrode 112 near sensing electrode 112 _AAnd the capacitor C between human body remainder and sensing electrode 112 _BSummation.If finger is not very close sensing electrode 112, so the finger and sensing electrode 112 between capacitor C _AAny variation generally all very little.As a result, by the change of electrical noise or interference, environmental characteristics, in the variation of the capacitor C c between human body and the ground and/or because the capacitor C between human body remainder and sensing electrode 112 that causes in the variable in distance between human body remainder and the sensing electrode 112 _BThe caused any outside common mode disturbances of variation or the like of variation, human dimension or characteristic may be equal to or greater than capacitor C between finger and sensing electrode 112 _ARespective change.

Therefore, if be adjusted to high sensitivity, owing to above-mentioned various outside common mode disturbances, may start unintentionally so near detector 100 based on the sensitivity near detector 100 of electric capacity.But, if based on electric capacity have muting sensitivity near detector 100, so may be because the user's that can not detect finger and a small amount of electric capacity between the sensing electrode 112 and can not work in appropriate distance near detector 100.

Utilization is worked more much betterly than non-contact switch based on the contact-making switch near detector 100 of electric capacity usually, because when finger contact contact-making switch surperficial, contact area is usually much larger than the area that only is finger tip.And, even it is the sensing electrode of contact-making switch is arranged on the insulating surface back, general also much smaller than the respective distance between the sensing electrode 112 of finger and non-contact switch in the distance between the sensing electrode of finger and contact-making switch.Therefore change much larger than the corresponding capacitance between the sensing electrode 112 at finger and non-contact switch in the capacitance variations between the sensing electrode of finger and contact-making switch.Therefore, the capacitor C between the sensing electrode 112 of above-mentioned related detection and finger and non-contact switch _AThe capacitor C that for example causes of the problem of variation owing to the different users _BOr C _CThe relative contact-making switch of variation be unessential.

Avoid a kind of method of relevant with the outside common mode disturbances in the non-contact switch as mentioned above problem to be to use known differential signal measurement technology.This differential signal measurement technology can be used for following non-contact switch, this non-contact switch comprises two sensing electrodes, these two sensing electrodes be set to when by finger near first electric capacity that forms the sensing electrode is relative with near second electric capacity that is formed another sensing electrode by this finger when surpassing predetermined threshold value level starting switch.By in difference is measured, directly comparing these first and second electric capacity, whether start non-contact switch with decision, can eliminate the outside common mode disturbances that may influence measurement unfriendly effectively.

Submit to October 30 calendar year 2001, name is called the U.S. Patent No. 6 of DIFFERENTIAL TOUCH SENSORAND CONTROL CIRCUIT THEREFORE, 310,611 (' 611 patents) disclose a kind of touch sensor that uses the differential signal measurement technology.As disclosed in ' 611 patents, this touch sensor comprise first sensing electrode, position near second sensing electrode of first electrode, be connected to the differential circuit of first and second electrodes and be used between first and second electrodes, producing the pulse of electric field or other signal source.Although being used to carry out difference, measures by the touch sensor of ' 611 patents, but this touch sensor is not to operate by measurement electric capacity, but by measuring the voltage difference variation of object cause between two sensing electrodes that influences two electrodes electric field on every side owing to introducing.This touch sensor uses differential circuit that the output signal of the voltage difference between two electrodes of response is provided.

But disclosed touch sensor has defective when being used to realize non-contact switch in ' 611 patents.For example, by introduce the above-mentioned voltage difference variation of object cause between two sensing electrodes of touch sensor be by the electric field relevant with this object with sensing electrode interaction caused.The interaction of this electric field is relatively complicated, because two sensing electrodes are in different voltage potentials with this object, and the voltage difference between two sensing electrodes changes and this object does not concern near the degree of sensing electrode is accurate.In addition, the method for the voltage difference between the disclosed measurement sensing electrode is only just effective when the voltage difference is equally enough big under the such situation of contact-making switch in ' 611 patents.Therefore, in ' 611 patents disclosed method be inadequately accurately or sensitivity be used for non-contact switch.

The U.S. Patent No. 6,456,477 (' 477 patent) that on September 24th, 2002 submitted to, name is called LINEAR CAPACITANCE DETECTIONCIRCUIT discloses a kind of capacitive detection circuit that uses the differential signal measurement technology.As disclosed in ' 477 patents, the linear capacitance testing circuit comprises by measure the circuit of the electric capacity difference between first capacitor and second capacitor with two capacitors of pulsed drive.This capacitive detection circuit also comprises having degenerative operational amplifier, and this negative feedback is used to make two capacitors to remain on the basic voltage potential that equates.As a result, between the capacitance ratio of the signal of telecommunication that operational amplifier produces and two capacitors, there is linear relationship.But disclosed method also has defective in ' 477 patents, that is, it needs pulse signal, and pulse signal may bring instantaneous noise and instability to operational amplifier, and can influence the accuracy of operational amplifier output nocuously.Though can use low pass filter and feedback condenser to relax transient noise and unsettled influence at the input of operational amplifier, add accuracy and sensitivity that this member influences capacitive detection circuit unfriendly.

Therefore, need a kind of capacitance measuring device of avoiding the defective in the said method and technology and use the capacitance measurement technology that can avoid the defective in the said method near detector (for example non-contact switch).

Summary of the invention

According to the present invention, a kind of capacitance measuring device and technology are provided, can be used to improve the sensitivity and the accuracy of capacitive transducer, proximity transducer and the non-contact switch of number of different types.Capacitance measuring device disclosed herein directly and accurately has (offset) linear response that can adjust side-play amount to the electric capacity of capacitor/capacitive transducer with each rate of change generation of the electric capacity of one or more other different capacitor/capacitive transducers, and makes all capacitor/capacitive transducers keep essentially identical voltage potential always.Capacitance measuring device disclosed herein also multiply by first invariant and the electric capacity of one or more other different capacitor/capacitive transducers to the electric capacity of capacitor/capacitive transducer and all multiply by each difference between corresponding second invariant and change and produce linear response, and makes all capacitor/capacitive transducers keep essentially identical voltage potential always.

In addition, capacitance measuring device disclosed herein directly and accurately to the capacitance variations of capacitor/capacitive transducer or electric capacity reciprocal change to produce have the linear response that can adjust side-play amount, and in capacitance on a large scale, do not needing special calibration or adjusting.Capacitance measuring device disclosed herein also provides a kind of straightforward procedure of measuring the electric capacity or the electric capacity inverse of a large amount of capacitor/capacitive transducers, perhaps the straightforward procedure that the electric capacity of the electric capacity of a large amount of capacitor/capacitive transducers and a large amount of group capacitor/capacitive transducers is compared.

Capacitance measuring device disclosed herein uses a plurality of operational amplifiers, is used to make the voltage potential of many capacitor/capacitive transducers to remain under the essentially identical voltage potential always and compares or measure.Because this many capacitor/capacitive transducer remains on essentially identical voltage potential, so there is not electric capacity between them basically.Therefore, even when capacitor/capacitive transducer is nearer toward each other, this capacitance measuring device also can be used to measure the small amount of capacitance variation of many capacitor/capacitive transducers, and near capacitor/capacitive transducer can not influence this capacitance measurement.

In one embodiment, capacitance measuring device comprises first operational amplifier A 1 and second operational amplifier A 2 that is configured to difference amplifier.Here the term difference amplifier of Shi Yonging is meant circuit or the device that amplifies the difference between two input signals, comprises dissimilar difference direct current amplifiers, for example instrument amplifier or the like.One end of two capacitor C1 that are compared or measure and each among the C2 is connected to the circuit ground end, and the other end is connected to a differential input end of operational amplifier A 1.Capacitor C1 is connected to the inverting terminal of operational amplifier A 1, and capacitor C2 is connected to the in-phase input end of operational amplifier A 1.Process is connected to the respective resistors of the respective input of operational amplifier A 1, and capacitor C1 and C2 are driven by the output of cyclic variation voltage source, for example sinusoidal voltage source.Feedback resistor is connected between the output and its inverting terminal of operational amplifier A 1.Because the open-loop gain that operational amplifier A 1 is high, capacitor C1 and C2 keep essentially identical voltage potential always.Between the ratio of the electric capacity of the electric capacity of the magnitude of current that flows through feedback resistor and capacitor C1 and capacitor C2, there is linear relationship.And, the electric current that flows through feedback resistor and the electric current homophase or the out-phase that flow through the resistor that is connected to the cyclic variation voltage source, this depends on that this ratio is less than or greater than designated value.The phase place and the amount that flow through the electric current of feedback resistor can be measured by difference amplifier A2, and its differential input end is connected to the output of operational amplifier A 1, and another differential input end is connected to a differential input end of operational amplifier A 1.

In a second embodiment, capacitance measuring device comprises first operational amplifier A 1 and second operational amplifier A 2 that is configured to difference amplifier.One end of two capacitor C1 that are compared or measure and each among the C2 is connected to the circuit ground end, and the other end is connected to a differential input end of operational amplifier A 1.Capacitor C1 is connected to the inverting terminal of operational amplifier A 1, and capacitor C2 is connected to the in-phase input end of operational amplifier A 1.The in-phase input end of operational amplifier A 1 is directly driven by the output in period 1 variable-current source, sinusoidal current source for example, and the inverting terminal of operational amplifier A 1 is directly driven by property second round variable-current source, the output in property second round variable-current source be period 1 property variable-current source output K (constant) doubly.Feedback resistor is connected between the output and its inverting terminal of operational amplifier A 1.Because the open-loop gain that operational amplifier A 1 is high, capacitor C1 and C2 keep essentially identical voltage potential always.Between the ratio of the electric capacity of the electric capacity of the magnitude of current that flows through feedback resistor and capacitor C1 and capacitor C2, there is linear relationship.And, flowing through the output homophase or the out-phase of the electric current and the cyclic variation current source of feedback resistor, this depends on that this ratio is less than or greater than the K value.The phase place and the amount that flow through the electric current of feedback resistor can be measured by difference amplifier A2, and its differential input end is connected to the output of operational amplifier A 1, and another differential input end is connected to a differential input end of operational amplifier A 1.

In the 3rd embodiment, capacitance measuring device comprises first and second operational amplifier A 0 and A1 and the 3rd operational amplifier A 2 that is set to difference amplifier.Be compared or measurement and correspondingly have two capacitor C1 of electric capacity c1 and c2 and each the end among the C2 is connected to the circuit ground end, the other end is connected to the inverting terminal of operational amplifier A 0 or A1.Capacitor C1 is connected to the inverting terminal of operational amplifier A 1, and capacitor C2 is connected to the inverting terminal of operational amplifier A 0.The in-phase input end of operational amplifier A 0 and A1 is all directly driven by the cyclic variation voltage source, for example sinusoidal voltage source.The first feedback resistor R1 with resistance r1 is connected between the output and its inverting terminal of operational amplifier A 1.The second feedback resistor R2 with resistance r2 is connected between the output and its inverting terminal of operational amplifier A 0.Because operational amplifier A 0 and the high open-loop gain of A1, two capacitor C1 and C2 keep and the essentially identical voltage potential of cyclic variation voltage source always.The output of operational amplifier A 1 is connected to the in-phase input end of difference amplifier A2, and the output of operational amplifier A 0 is connected to the inverting terminal of difference amplifier A2.The output of difference amplifier A2 with (r1 * c1-r2 * c2) be directly proportional, and with the electric current homophase or the out-phase that flow through resistor R 1 and R2, this depend on (r1 * c1-r2 * c2) be greater than or less than zero.

The embodiment of each capacitance measuring device disclosed herein can be set to be used for the electric capacity of comparison capacitor/capacitive transducer and the electric capacity of a plurality of other different capacitors/capacitive transducers, makes all capacitor/capacitive transducers keep essentially identical voltage potential simultaneously.In addition, by make the incision of each capacitor/capacitive transducer or cut out subsequently relatively or measure, the embodiment of each capacitance measuring device can in turn measure the electric capacity of many capacitor/capacitive transducers or the inverse of electric capacity, the perhaps electric capacity of the electric capacity of more many capacitor/capacitive transducers and many group capacitor/capacitive transducers.

Non-contact switch and the proximity transducer of the embodiment that uses capacitance measuring device disclosed herein are provided in addition.Non-contact switch is set to start by finger or finger-like object, needs to point before starting switch or the finger-like object reaches the bounds of appointment.This non-contact switch has less susceptibility to starting unintentionally, and has less sensitiveness to the variation of environmental factor (for example temperature, humidity or the like) with to electrical noise, and has simple and firm structure.This non-contact switch can be used for the available multiple facilities and equipment of application apparatus, Industry Control panel and the public of health sensitivity (hygiene-sensitive), including, but not limited to elevator, automatic vending machine, secure access panel, information terminal or the like.

In one embodiment, non-contact switch comprise positive and be arranged on the switch front above or the back, keep the sensing electrode of two vicinities of identical voltage potential basically.As a result, between two sensing electrodes, there is not electric capacity basically, so sensing electrode operation independently of one another basically.A sensing electrode is a central electrode, and another sensing electrode is an outer electrode.Central electrode and outer electrode separate, and are centered on by outer electrode to small part.When finger or finger-like the tip of anything near or during near central electrode, utilize the embodiment of disclosed capacitance measuring device here can detect the existence of finger or finger-like object.This capacitance measuring device can be used to measure the ratio of two sensing electrodes with respect to the electric capacity of finger or finger-like object, perhaps measure at a sensing electrode and multiply by first invariant with respect to the finger or the electric capacity of finger-like object, and another sensing electrode multiply by difference between second invariant with respect to finger or the electric capacity of finger-like object, therefore eliminate outside common mode disturbances basically, the changes in capacitance between human body remainder and sensing electrode for example, environmental change, electrical noise or the like, because they are closely approaching each other, so these outside common mode disturbances can influence two sensing electrodes comparably.Relative position by fixing geometry, size and two sensing electrodes promotes capacitance ratio and difference that capacitance measuring device carries out to measure.Outer electrode can the centre electrode the front, make that at first capacitance ratio or difference measured value are less than preset threshold value when finger or finger-like object are shifted to central electrode.Along with finger or the more and more close central electrode of finger-like object, capacitance ratio or difference measured value surpass preset threshold value at last, thereby starting switch.Non-contact switch can also comprise around the guard electrode of two sensing electrode back sides and side.Guard electrode and sensing electrode keep essentially identical voltage potential, so each sensing electrode only can form capacitor with the object that is arranged on its front.Can also protect the lead that extends to capacitance measuring device from two sensing electrodes with biaxial cable or two coaxial cables, wherein the external conductor of cable is used as protective shielding, and keeps essentially identical voltage potential with the inner conductor that is connected to the cable of sensing electrode.The form of vessel surface can be taked in the front of non-contact switch, and wherein the edge of vessel surface touches off a finger or the finger-like object must reach imaginary boundary face with starting switch.

Capacitance measuring device disclosed herein can be used to detect approaching greater than the conductive body of finger, for example palm of staff.Capacitance measuring device disclosed herein can also be used to detect position, the location of the conductive body (for example people's appendage) in specified scope and/or move.

From following " detailed description of the present invention " can other characteristics obviously of the present invention, function and aspect.

The accompanying drawing summary

Invention will be more fully understood with reference to following " detailed description of the present invention " in conjunction with the accompanying drawings, wherein:

Fig. 1 is illustrated in human body, ground and is connected to the various equivalent capacitys that form between the sensing electrode of capacitance sensing circuit;

Fig. 2 a is the schematic diagram according to first capacitance measurement circuit of the present invention;

Fig. 2 b is to use the schematic diagram of the circuit of first capacitance measurement circuit among Fig. 2 a, and this circuit is used to produce the linear response to the variation of each ratio of the electric capacity of the electric capacity of capacitor and one or more other different capacitors;

Fig. 3 a is the schematic diagram according to second capacitance measurement circuit of the present invention;

Fig. 3 b is to use the schematic diagram of the circuit of second capacitance measurement circuit among Fig. 3 a, and this circuit is used to produce the linear response to the variation of each ratio of the electric capacity of the electric capacity of capacitor and one or more other different capacitors;

Fig. 4 a is the schematic diagram according to the 3rd capacitance measurement circuit of the present invention;

Fig. 4 b is to use the schematic diagram of the circuit of the 3rd capacitance measurement circuit among Fig. 4 a, this circuit is used to produce the linear response that each difference is changed, this difference be the electric capacity of capacitor multiply by first invariant and one or more other different capacitors electric capacity at it each multiply by after corresponding second invariant between difference;

Fig. 5 a-5d is the stereogram of the shape directly perceived in the front of non-contact switch according to the present invention;

Fig. 6 a-6d be respectively non-contact switch among Fig. 5 a-5d two sensing electrodes with and the positive arrangement directly perceived and the cross-sectional view of relative position;

Fig. 7 is according to the arrangement directly perceived of two sensing electrodes, front and guard electrode of non-contact switch of the present invention and the cross-sectional view of relative position;

Fig. 8 a is to use the diagrammatic sketch of non-contact switch of first capacitance measurement circuit of Fig. 2 a;

Fig. 8 b is to use the diagrammatic sketch of one group of non-contact switch of first capacitance measurement circuit of Fig. 2 a;

Fig. 9 a is to use the diagrammatic sketch of non-contact switch of second capacitance measurement circuit of Fig. 3 a;

Fig. 9 b is to use the diagrammatic sketch of one group of non-contact switch of second capacitance measurement circuit of Fig. 3 a;

Figure 10 a is to use the diagrammatic sketch of non-contact switch of the 3rd capacitance measurement circuit of Fig. 4 a; With

Figure 10 b is to use the diagrammatic sketch of one group of non-contact switch of the 3rd capacitance measurement circuit of Fig. 4 a.

Detailed description of the present invention

Here as a reference in conjunction with whole disclosures of following patent application, the name of submitting to June 15 in 2005 is called the U.S. Provisional Patent Application No.60/690 of " linear capacitance is measured and non-contact switch (LINEAR CAPACITANCEMEASUREMENT AND TOUCHLESS SWITCH) ", 486, the name of submitting on March 17th, 2005 is called the U.S. Provisional Patent Application No.60/601 of " the U.S. Provisional Patent Application No.60/662 of capacitance measurement and non-contact switch " (CAPACITANCE MEASUREMENT AND TOUCHLESS SWITCH) "; 378; name of submitting on October 19th, 2004 is called the U.S. Provisional Patent Application No.60/619 of " differential capacitance is measured and non-contact switch (DIFFERENTIAL CAPACITANCE MEASUREMENTAND TOUCHLESS SWITCH) "; the name of submitting on August 16th, 697 and 2004 is called " differential capacitance is measured and non-contact switch " (DIFFERENTIAL CAPACITANCE MEASUREMENTAND TOUCHLESS SWITCH) ", 610.

Disclose a kind of capacitance measuring device and technology, can be used to improve the sensitivity and the accuracy of many dissimilar capacitive transducers, proximity transducer and non-contact switch.Fig. 2 a illustrates first illustrative embodiment according to capacitance measurement circuit 200a of the present invention.In described embodiment, capacitance measurement circuit 200a comprises cyclic variation voltage source G1, first operational amplifier A 1 and is set to second operational amplifier A 2 of difference amplifier.Be compared and correspondingly have two capacitors/capacitive transducer C1 of electric capacity c1 and c2 and each the end among the C2 is connected to the circuit ground end, the other end is connected to a differential input end of operational amplifier A 1.Capacitor C1 is connected to the inverting terminal of operational amplifier A 1 at node 101, and capacitor C2 is connected to the in-phase input end of operational amplifier A 1 at node 102.

Node

101 and 102 corresponding output Vs by the cyclic variation voltage source G1 that passes through resistor R 1 and R2 drive, and this voltage source G1 can be a sinusoidal voltage source.Resistor R 1 has resistance r1, and resistor R 2 has resistance r2.The output V1 of operational amplifier A 1 feeds back to the inverting terminal of operational amplifier A 1 by the feedback resistor R3 with resistance r3.Because operational amplifier A 1 has very high open-loop gain, so two inputs of operational amplifier A 1 keep identical voltage potential basically, thereby effective RC time constant of capacitor C1 that makes in

node

101 and 102 and C2 is basic identical.The amount i2 that the amount i3 that flows through the electric current I 3 of resistor R 3 is substantially equal to flow into the electric current I 2 of capacitor C2 multiply by factor (r2/r1-c1/c2), i.e. i3=i2 * (r2/r1-c1/c2).The electric current I 3 that flows through resistor R 3 will and flow through electric current I 2 homophases or the out-phase of resistor R 2 with the electric current I 1 that flows through resistor R 1, and this depends on that capacitance ratio c1/c2 is less than or greater than value r2/r1.More particularly, if c1/c2 less than r2/r1, (r2/r1-c1/c2) is positive so, electric current I 2 and I3 will be homophases, if but c1/c2 greater than r2/r1, (r2/r1-c1/c2) bears so, electric current I 2 and I3 will be out-phase.When stable state, the amount i2 that flows into the electric current I 2 of capacitor C2 is the function of time, and the amount i3 that therefore flows through the electric current I 3 of resistor R 3 on a set time of the cycle of electric current I 3 is the accurate measurement of value (r2/r1-c1/c2).Voltage on the resistor R 3 equals i3 * r3, and equals the difference of the voltage potential between the output V1 of node 101 (or node 102) and operational amplifier A 1.This voltage can be by node 101 (or node 102) being connected to difference amplifier A2 one of two inputs and bring in measurement by another input that the output V1 with operational amplifier A 1 is connected to difference amplifier A2.Should be noted that the structure of describing difference amplifier A2 shown in Fig. 2 a here is in order to illustrate that other suitable circuit structure can also use.For example, the structure of alternative difference amplifier A2 can comprise the operational amplifier more than.The output Vd of difference amplifier A2 is directly proportional with the amount i3 of the electric current I 3 that flows through resistor R 3, and when c1/c2 during greater than r2/r1 will with electric current I 1 and I2 homophase.Notice that if the input of difference amplifier A2 is exchanged, the phase place of output Vd is also opposite.

Therefore, the output Vd of difference amplifier A2 is directly proportional with the signal of representative by the electric current I 2 of value (c1/c2-r2/r1) modulation.If electric current I 2 is sinusoidal, can utilize synchronous demodulator to measure the variation of capacitance ratio c1/c2 so.And, on a set time of output cycle the output Vd of (for example peak value of cycle), its just and/or the average absolute value of negative cycle or utilize signal (if the output Vs of voltage source G1 is sinusoidal) that synchronous demodulation extracts the Vd from output and capacitance ratio c1/c2 between have linear relationship.Therefore, if capacitor C2 has fixed capacity, output Vd on a set time of output cycle, its just and/or the average absolute value of negative cycle, perhaps utilize between signal that synchronous demodulation extracts from output and the electric capacity c1 and have linear relationship, if perhaps capacitor C1 has fixed capacity, then there is linear relationship between the inverse of they and electric capacity c2, this is useful especially when measuring distance, because for example the electric capacity between two plates and the distance between them are inversely proportional at two conductive bodies.

Fig. 2 b illustrates the circuit 200b that uses capacitance measurement circuit 200a1-200an, produce linear response in order to variation, and make all capacitor/capacitive transducers keep essentially identical voltage potential always each ratio of the electric capacity of the electric capacity of capacitor/capacitive transducer and one or more other different capacitors/capacitive transducers.Among corresponding a plurality of capacitors/capacitive transducer C11-C1n with electric capacity c11-c1n each and be connected the in-phase input end of operational amplifier A 0 and the electric capacity c2 of the capacitor between the earth terminal/capacitive transducer C2 compares (referring to Fig. 2 b).Among the capacitance measurement circuit 200a1-200an each all resembles capacitance measurement circuit 200a and (works a) referring to Fig. 2, except the voltage potential of capacitor C11-C1n is that output level with operational amplifier A 0 compares, and operational amplifier A 0 is set to voltage follower, goes up essentially identical voltage potential thereby produce with capacitor C2.Notice that capacitor C2 is driven by the output Vs of the voltage source G1 by resistor R 2.Therefore, on each set time of cycle of output Vd1-Vdn the output of (for example peak value of cycle), output Vd1-Vdn each just and/or the average absolute value of negative cycle or utilize signal (if the output Vs of voltage source G1 is sinusoidal) that synchronous demodulation extracts from output and capacitance ratio c11/c2 accordingly to have linear relationship to the c1n/c2.The result, if C2 has fixed capacity, so each of the output on each set time of cycle of output Vd1-Vdn, output Vd1-Vdn just and/or the average absolute value of negative cycle or utilize signal that synchronous demodulation extracts from output and electric capacity c11 accordingly to have linear relationship to the c1n.

Fig. 3 a illustrates second illustrative embodiment according to capacitance measurement circuit 300a of the present invention.In described embodiment, capacitance measurement circuit 300a comprises cyclic variation current source G1 and G2, first operational amplifier A 1 and second operational amplifier A 2 that is set to difference amplifier.Be compared and correspondingly have two capacitors/capacitive transducer C1 of electric capacity c1 and c2 and each the end among the C2 is connected to the circuit ground end, the other end is connected to a differential input end of operational amplifier A 1.Capacitor C1 is connected to the inverting terminal of operational amplifier A 1 at node 101, and capacitor C2 is connected to the in-phase input end of operational amplifier A 1 at node 102.Node 102 is driven by the output current I2 of cyclic variation current source G2.Node 101 is driven by the output current I1 of cyclic variation current source G1, and wherein I1 equals K I2 doubly, and K is the constant more than or equal to zero.The output V1 of operational amplifier A 1 feeds back to its inverting terminal by the feedback resistor R1 with resistance r1.Because operational amplifier A 1 has very high open-loop gain, so two inputs of operational amplifier A 1 keep essentially identical voltage potential.Therefore, the amount i2 that the amount i3 that flows through the electric current I 3 of resistor R 1 is substantially equal to flow into the electric current I 2 of capacitor C2 multiply by factor (K-c1/c2), i.e. i3=i2 * (K-c1/c2).Flow through resistor R 1 electric current I 3 will with electric current I 1 and I2 homophase or out-phase, this depends on that capacitance ratio c1/c2 is less than or greater than K.More particularly, if c1/c2 less than K, (K-c1/c2) is positive so, electric current I 2 and I3 will be homophases, if but c1/c2 greater than K, (K-c1/c2) bears so, electric current I 2 and I3 will be out-phase.When stable state, the amount i2 that flows into the electric current I 2 of capacitor C2 only is the function of time, and the amount i3 that therefore flows through the electric current I 3 of resistor R 1 on a set time of the cycle of electric current I 3 is the accurate measurement of value (K-c1/c2).Voltage on the resistor R 1 is substantially equal to i3 * r1, and equals the difference of the voltage potential between the output V1 of node 101 (or node 102) and operational amplifier A 1.Voltage on the resistor R 1 can be by node 101 (or node 102) being connected to difference amplifier A2 one of two inputs and bring in measurement by another input that the output V1 with operational amplifier A 1 is connected to difference amplifier A2.Should be noted that the structure of describing difference amplifier A2 shown in Fig. 3 a here is in order to illustrate that other suitable circuit structure can also use.For example, the structure of alternative difference amplifier A2 can comprise more than one operational amplifier.The output Vd of difference amplifier A2 is directly proportional with the amount i3 of the electric current I 3 that flows through resistor R 1, and when capacitance ratio c1/c2 during greater than K will with electric current I 1 and I2 homophase.Notice that if the input of difference amplifier A2 is exchanged, the phase place of output Vd is also opposite.Therefore, the output Vd of difference amplifier A2 is proportional by the signal of the electric current I 2 of value (c1/c2-K) modulation with representative.If constant K equals 0, promptly there is not current source G1, the output Vd of difference amplifier A2 is directly proportional with the signal of representative by the electric current I 2 of value c1/c2 modulation.If electric current I 2 is sinusoidal,, can utilize synchronous demodulator to measure the variation of capacitance ratio c1/c2 so for all K values.And, on a set time of output cycle the output Vd of (for example peak value of cycle), its just and/or the average absolute value of negative cycle or utilize signal (if the output I2 of current source G2 is sinusoidal) that synchronous demodulation extracts from output and capacitance ratio c1/c2 between have linear relationship.Therefore, if capacitor C2 has fixed capacity, the output Vd on the set time of output cycle, its just and/or the average absolute value of negative cycle or utilize signal that synchronous demodulation extracts from output and electric capacity c1 between have linear relationship, if perhaps capacitor C1 has fixed capacity, then there is linear relationship between the inverse of they and electric capacity c2, this is useful especially when measuring distance, because for example the electric capacity between two plates and the distance between them are inversely proportional at two conductive bodies.Should be noted that if current source G1 and G2 have sizable DC component in their output, can between the two ends of capacitor C1 and C2, bypassed resistor be set so.

Fig. 3 b illustrates the circuit 300b that uses capacitance measurement circuit 300a1-300an, it produces linear response in order to the variation to each ratio of the electric capacity of the electric capacity of capacitor/capacitive transducer and one or more other different capacitors/capacitive transducers, and makes all capacitor/capacitive transducers keep essentially identical voltage potential always.Corresponding have each capacitor/capacitive transducer C11-C1n of electric capacity c11-c1n and be connected the in-phase input end of operational amplifier A 0 and the electric capacity c2 of the capacitor between the earth terminal/capacitive transducer C2 compares (referring to Fig. 3 b).Capacitor C11-C1n is corresponding to be driven by current source G11-G1n.Among each output I11-I1n of current source G11-G1n each equals I2 and multiply by corresponding constant K 11-K1n, and wherein each of constant K 11-K1n is all more than or equal to zero.Among the capacitance measurement circuit 300a1-300an each all resembles capacitance measurement circuit 300a and (works a) referring to Fig. 3, except the voltage potential of capacitor C11-C1n is that output level with operational amplifier A 0 compares, and operational amplifier A 0 is set to voltage follower, thereby produce with capacitor C2 and go up essentially identical voltage potential, this capacitor C2 is driven by the output I2 of current source G2.Therefore, on each set time of cycle of output Vd1-Vdn the output of (for example peak value of cycle), output Vd1-Vdn each just and/or the average absolute value of negative cycle or utilize signal (if the output I2 of current source G2 is sinusoidal) that synchronous demodulation extracts from output and capacitance ratio c11/c2 accordingly to have linear relationship to the c1n/c2.The result, if C2 has fixed capacity, so each of the output on each set time of cycle of output Vd1-Vdn, output Vd1-Vdn just and/or the average absolute value of negative cycle or utilize signal that synchronous demodulation extracts from output and electric capacity c11 accordingly to have linear relationship to the c1n.

Fig. 4 a illustrates the 3rd illustrative embodiment according to capacitance measurement circuit 400a of the present invention.In described embodiment, capacitance measurement circuit 400a comprises cyclic variation voltage source G1, first operational amplifier A 0, second operational amplifier A 1 and is set to the 3rd operational amplifier A 2 of difference amplifier.Be compared and correspondingly have two capacitors/capacitive transducer C1 of electric capacity c1 and c2 and each the end among the C2 is connected to the circuit ground end, the other end is connected to the inverting terminal of operational amplifier A 0 exclusive disjunction amplifier A1.Capacitor C1 is connected to the inverting terminal of operational amplifier A 1 at node 101, and capacitor C2 is connected to the inverting terminal of operational amplifier A 0 at node 102.The first feedback resistor R1 with resistance r1 is connected between the output and its inverting terminal of operational amplifier A 1.Equally, the second feedback resistor R2 with resistance r2 is connected between the output and its inverting terminal of operational amplifier A 0.The in-phase input end of operational amplifier A 1 and A0 is all driven by the output Vs of cyclic variation voltage source G1, and this voltage source G1 can be a sinusoidal voltage source.Because the high open-loop gain of operational amplifier A 1 and A0, so capacitor C1 and C2 keep the essentially identical voltage potential of output Vs with voltage source G1 always.V0 is the output of operational amplifier A 0, and V1 is the output of operational amplifier A 1.(V1-Vs) equal the time-derivative value of multiply by (r1 * c1), i.e. (V1-Vs)=r1 * c1 * dVs/dt, and and flow through electric current I 1 homophase that resistor R 1 enters capacitor C1 of Vs.(V0-Vs) equal the time-derivative value of multiply by (r2 * c2), i.e. (V0-Vs)=r2 * c2 * dVs/dt, and and flow through electric current I 2 homophases that resistor R 2 enters capacitor C2 of Vs.Offer the in-phase input end of difference amplifier A2 as the output V1 of operational amplifier A 1, and the output V0 of operational amplifier A 0 is when offering the inverting terminal of difference amplifier A2, (r1 * c1-r2 * c2) signal of the time-derivative of the Vs of modulation is directly proportional the output Vd of difference amplifier A2 by value with representative, and with the electric current homophase or the out-phase that flow through resistor R 1 and R2, this depends on (r1 * c1-r2 * c2) be greater than or less than zero (if exchange to the input of difference amplifier A2, the phase place of output Vd is just opposite).Should be noted that the structure of describing difference amplifier A2 shown in Fig. 4 a here is in order to illustrate that other suitable circuit structure can also use.For example, the structure of alternative difference amplifier A2 can comprise more than one operational amplifier.If voltage Vs is sinusoidal, can utilize synchronous demodulator to measure the (variation of the value of r1 * c1-r2 * c2) so.Under stable state, the time-derivative of Vs only is the function of time, therefore, on a set time of output cycle the output Vd of (for example peak value of cycle), its just and/or the average absolute value of negative cycle or utilize signal (if the output Vs of voltage source G1 is sinusoidal) that synchronous demodulation extracts and (there is linear relationship in value between r1 * c1-r2 * c2) from output.The result, if C2 has fixed capacity, so the output Vd of set time of output cycle, its just and/or the average absolute value of negative cycle or utilize signal that synchronous demodulation extracts from output and electric capacity c1 between have linear relationship, if perhaps capacitor C1 has fixed capacity, just and between the electric capacity c2 there is linear relationship in they so.

Fig. 4 b illustrates the circuit 400b that uses capacitance measurement circuit 400a1-400an, its in order to the electric capacity to capacitor/capacitive transducer multiply by first invariant, and the electric capacity of one or more other different capacitors/capacitive transducers after each multiply by corresponding second invariant between each difference change and produce linear response, and make all capacitor/capacitive transducers keep essentially identical voltage potential always.Among corresponding capacitor/capacitive transducer C11-C1n with electric capacity c11-c1n each and the electric capacity c2 of capacitor/capacitive transducer C2 compare.Each capacitance measurement circuit 400a1-400an that combines with operational amplifier A 0, feedback resistor R2 and capacitor C2 resembles capacitance measurement circuit 400a and (works a) referring to Fig. 4.Therefore, on each set time of cycle of output Vd1-Vdn the output of (for example peak value of cycle), output Vd1-Vdn each just and/or the average absolute value of negative cycle or utilize signal (if the output Vs of voltage source G1 is sinusoidal) that synchronous demodulation extracts and value accordingly from output (have linear relationship between r1n * c1n-r2 * c2), wherein " r1n " is the resistance of the respective feedback resistor R 1n that is associated with corresponding operational amplifier A 1n.Therefore, if capacitor C2 has fixed capacity, so each of the output on each set time of cycle of output Vd1-Vdn, output Vd1-Vdn just and/or the average absolute value of negative cycle or utilize signal that synchronous demodulation extracts and have linear relationship between the electric capacity c11-c1n accordingly from output.

By making the incision of capacitor/capacitive transducer and cutting out subsequently measurement, each embodiment of capacitance measurement circuit disclosed herein can in turn change generation linear response, the perhaps electric capacity of the electric capacity of more many capacitor/capacitive transducers and many group capacitor/capacitive transducers to the capacitance variations of a large amount of capacitor/capacitive transducers or the inverse of electric capacity.Please note, can in each embodiment of above-mentioned capacitance measurement circuit, use the capacitive transducer of any suitable type, including, but not limited to being used for the capacitive transducer of any suitable type that detection power, pressure, tension force, acceleration, sound, mechanical displacement, fluid flows or the like.Should also be noted that, each embodiment of above-mentioned capacitance measurement circuit can use any suitable type both-end power supply (double-ended power supply) if or when suitable circuit ground benchmark can be provided for example by bleeder circuit (voltage splitter circuit), can use the single ended power supply (single-ended power supply) of any suitable type.

Fig. 5 a-5d illustrates the illustrative embodiment according to non-contact switch of the present invention front.The form of any suitable type of container can be taked in the front of non-contact switch disclosed herein, for example the container 500a-500c that illustrates respectively of Fig. 5 a-5c.Shown in Fig. 5 a-5c, each container 500a-500c comprises as the base part of the base part 502a-502c that resembles Fig. 5 a-5c accordingly and as the marginal portion of the marginal portion 504a-504c of corresponding Fig. 5 a-5c.The front of switch can also resemble the positive 500d (referring to Fig. 5 d) smooth, or any other suitable surface configuration.Non-contact switch disclosed herein comprises the top or back that is arranged on the switch front and keeps two sensing electrodes of essentially identical voltage potential, specifically a central electrode and an outer electrode.Central electrode and outer electrode separate, and are centered on by outer electrode to small part.Center and outer electrode can have any suitable shape, form or size, and can not be the solid block parts, and for example electrode can be the lead aperture plate.Fig. 6 a-6d illustrates center and outer electrode respectively toward each other and with respect to illustrative arrangement and the position of the positive 500a-500d of Fig. 5 a-5d.Shown in Fig. 6 a-6c, when the front was vessel form, central electrode was arranged near the substrate of container, and outer electrode is arranged near the edge of container.

Utilize the embodiment of disclosed capacitance measurement circuit here, can detect near the non-contact switch central electrode or near the finger of central electrode or the existence of finger-like the tip of anything.When detecting the existing of finger or finger-like object, near the electric capacity of the capacitor that capacitance measurement circuit is relatively formed by finger or finger piece body two sensing electrodes (being central electrode and outer electrode), therefore eliminate outside common mode disturbances, for example changes in capacitance between human body remainder and sensing electrode, environmental change, electrical noise or the like basically.Because they are closely close each other, so these outside common mode disturbances can influence two sensing electrodes comparably.In addition, outer electrode can be arranged at that a position made before starting switch in the non-contact switch, and finger or finger-like the tip of anything will be through the borders of appointment.In one embodiment, this finishes by following the setting: the distance that outer electrode is arranged on the appointment of central electrode front, but and dispose the spacing of two sensing electrodes and their relative surface area make when object near electrode decentre electrode above appointment apart from the time, near the ratio of the electric capacity that externally forms the electrode near the electric capacity that forms the central electrode and by this object by object, perhaps near the electric capacity that is formed central electrode by this object multiply by first constant, and multiply by difference between second constant by near the electric capacity that this object externally forms the electrode, less than preset threshold value.Should be appreciated that capacitance ratio and difference measurement are that embodiment by above-mentioned capacitance measurement circuit carries out, and promote this measurement by fixing geometry, size and the relative position of two sensing electrodes.In one embodiment, when the capacitance ratio of measuring or difference surpass preset threshold value, start non-contact switch.

Therefore, finger or finger-like object do not start non-contact switch, pass the border of appointment up to finger.If the front of non-contact switch has the form of vessel surface, (for example referring to Fig. 5 a-5c), the border of appointment is consistent with the imaginary plane of container edge institute cropping.Along with finger or finger-like the tip of anything are shifted to central electrode, and the plane on the border of breakthrough appointment, the electric capacity increase that capacity ratio relevant with central electrode and outer electrode are relevant is faster.Multiply by first constant and when relevant electric capacity multiply by difference between second constant and surpasses preset threshold value, start non-contact switch when the capacitance ratio relevant or at the electric capacity relevant with outer electrode with central electrode with central electrode and outer electrode.

Fig. 7 illustrates the illustrative embodiment according to non-contact switch 700 of the present invention.In an illustrated embodiment, non-contact switch 700 comprises front 702, central electrode 704, the outer electrode 706 of vessel form and the guard electrode 708 that centers on two sensing electrode 704,706 back sides and side.All electrodes 704,706,708 keep essentially identical voltage potential.As a result, two sensing electrodes 704,706 only can and be positioned between the object of switch front (promptly on switch shown in Figure 7 700) at sensing electrode and form electric field.Can also protect the lead that extends to capacitance measurement circuit from two sensing electrodes with biaxial cable or two coaxial cables, wherein the external conductor of cable is used as protective shielding, and keeps essentially identical voltage potential with the inside cable conductor that is connected to sensing electrode.

Fig. 8 a illustrates the first illustrative circuit equipment 800a according to non-contact switch of the present invention.Shown in Fig. 8 a, circuit arrangement 800a comprises central electrode E1, outer electrode E2, guard electrode E3, start delay part (startup delay section) 203, switch deciding section 205, switch output 207 and capacitance measurement circuit 802a, and this capacitance measurement circuit 802a comprises cyclic variation voltage source G1, operational amplifier A 0 and A1, resistor R 1-R3 and the operational amplifier A 2 that is set to difference amplifier.Central electrode E1 is connected to the inverting terminal of operational amplifier A 1 at node 201, outer electrode E2 is connected to the in-phase input end of operational amplifier A 0 at node 202, operational amplifier A 0 is set to voltage follower, thereby the in-phase input end of the voltage potential of outer electrode E2 to operational amplifier A 1 is provided.Node 201 and 202 two are driven by the output Vs of cyclic variation voltage source G1.Electrode E1 and E2 are corresponding to corresponding capacitor C1 of Fig. 2 a and C2.Guard electrode E3 is connected to the output of operational amplifier A 0, so the voltage potential of guard electrode E3 is substantially equal to the voltage potential of sensing electrode E1 and E2.Guard electrode E3 can be set to the back side and the side around sensing electrode E1 and E2, therefore can only form electric capacity between the conductive body of non-contact switch front and sensing electrode E1 and E2.Note, the operational amplifier A 1 of Fig. 8 a and A2 resemble corresponding operational amplifier A 1 of Fig. 2 a and A2, the resistor R 2 of Fig. 8 a resembles the resistor R 2 of Fig. 2 a, the resistor R 1 of Fig. 8 a and R3 resemble corresponding resistor R 1 of Fig. 2 a and R3, and the cyclic variation voltage source G1 of Fig. 8 a resembles the cyclic variation voltage source G1 of Fig. 2 a.Therefore, on a set time of output cycle the output Vd of the difference amplifier A2 of (for example peak value of cycle), its just and/or the average absolute value of negative cycle or utilize between signal (if the output Vs of voltage source G1 is sinusoidal) that synchronous demodulation extracts from output and the electric capacity relevant ratio and have linear relationship to the electric capacity of being correlated with outer electrode E2 with central electrode E1.Difference amplifier A2 provides output Vd to switch deciding section 205, and switch deciding section 205 is according to signal Vd decision whether startup non-contact switch.For example, switch deciding section 205 can decide according to phase place, amplitude, mean value and/or any other suitable speciality of signal Vd.Selectively, switch deciding section 205 may need the phase place of desired signal Vd of specified quantity and/or the continuous detecting of amplitude before decision starts non-contact switch, perhaps satisfy some requirement.If voltage Vs is sinusoidal, can in switch deciding section 205, introduce synchronous demodulator so, even make under high noise levels, also can obtain the rate of change of the electric capacity relevant pair electric capacity of being correlated with high accuracy with outer electrode E2 with central electrode E1.It should be noted that switch deciding section 205 may also need one or more signals to determine whether starting switch except that signal Vd.For example, switch deciding section 205 may need reference signal to decide the phase place of signal Vd.Switch deciding section 205 provides the logical signal 206 of representing its decision to switch output 207, realizes required switch motion.Please note, logic output (normally high or low), solid-state switch output and/or dry contact output (normally opening or closure) that switch output 207 can utilize any suitable quantity realize including, but not limited to pulse mode, moment mode (momentarily mode), triggering folding mode or the like with any suitable on-off mode.Switch output 207 can also be set to produce audio frequency and/or video output, thus the state of indication non-contact switch.Because capacitance measurement circuit 802a need experience several cycles of the output Vs of voltage source G1 and reach stable, so in start-up period, start delay part 203 output enabling signals 204 are given switch deciding section 205, in case switch deciding section 205 starting switch unintentionally.When sensing electrode E1 and E2 are set to separate the input certain distance of operational amplifier A 0 and A1, can utilize biaxial cable or two isometric coaxial cables to protect lead from central electrode E1 and outer electrode E2, be connected to the protective shielding of guard electrode E3 with the external conductor conduct, and keep and be connected to the essentially identical voltage potential of inner conductor of each sensing electrode E1 and E2, therefore can not introduce stray capacitance, and basic any other injurious effects introduced by lead of eliminating.

Fig. 8 b illustrates the first illustrative circuit equipment 800b of one group of non-contact switch, comprises cyclic variation voltage source G1, operational amplifier A 0, capacitance measurement circuit 802a1-802an, start delay part 203, switch deciding section 205 and switch output 207.Note that among the capacitance measurement circuit 802a1-802an that combines with operational amplifier A 0 each resembles capacitance measurement circuit 802a (referring to Fig. 8 a), and corresponding to corresponding non-contact switch in this group non-contact switch.Particularly, the electrode E2 that is connected to the in-phase input end of operational amplifier A 0 corresponds to the public outer electrode of this group non-contact switch, and the electrode E3 that is connected to operational amplifier A 0 output corresponds to the public guard electrode of this group non-contact switch.Among the electrode E11-E1n each is corresponding to the central electrode of corresponding non-contact switch.Please note, the operational amplifier A 0 of Fig. 8 b resembles the operational amplifier A 0 of Fig. 2 b, the operational amplifier A 11-A1n of Fig. 8 b resembles the corresponding operational amplifier A 11-A1n of Fig. 2 b, the difference amplifier A21-A2n of Fig. 8 b resembles the corresponding difference amplifier A21-A2n of Fig. 2 b, the resistor R 2 of Fig. 8 b resembles the resistor R 2 of Fig. 2 b, the resistor R 11-R1n of Fig. 8 b resembles the corresponding resistor R 11-R1n of Fig. 2 b, the resistor R 31-R3n of Fig. 8 b resembles the corresponding resistor R 31-R3n of Fig. 2 b, and the cyclic variation voltage source G1 of Fig. 8 b resembles the cyclic variation voltage source G1 of Fig. 2 b.Difference amplifier A21-A2n provides corresponding output signal Vd1-Vdn to switch deciding section 205, and switch deciding section 205 is according to corresponding each switch of signal Vd1-Vdn decision when the startup.Switch deciding section 205 provides the logical signal 206 of representing its corresponding decision to switch output 207, and switch output 207 is realized the required switch motion of each switch.Please note, switch output 207 can utilize logic output (normally high or low), solid-state switch output and/or the dry contact output (normally open or closed) of any suitable quantity, with any suitable on-off mode including, but not limited to pulse mode, moment mode, trigger folding mode or the like and realize each switch.Switch output 207 can also be set to produce audio frequency and/or video output, thereby indicates the state of each switch.With reference to the described appropriate section 203 of figure 8a, and the switch that each switch of circuit arrangement 800b (referring to Fig. 8 b) resembles circuit arrangement 800a basically (was worked a) referring to Fig. 8 above the start delay part 203 of Fig. 8 b resembled.

Fig. 9 a illustrates the second illustrative circuit equipment 900a according to non-contact switch of the present invention.Shown in Fig. 9 a, circuit arrangement 900a comprises central electrode E1, outer electrode E2, guard electrode E3, start delay part 203, switch deciding section 205, switch output 207 and capacitance measurement circuit 902a, and this capacitance measurement circuit 902a comprises cyclic variation current source G1 and G2, operational amplifier A 0 and A1, resistor R 1 and the operational amplifier A 2 that is set to difference amplifier.Central electrode E1 is connected to the inverting terminal of operational amplifier A 1 at node 201, outer electrode E2 is connected to the in-phase input end of operational amplifier A 0 at node 202, operational amplifier A 0 is set to voltage follower, thereby the in-phase input end of the voltage potential of outer electrode E2 to operational amplifier A 1 is provided.Node 201 is driven by the output current I1 of cyclic variation current source G1, and node 202 is driven by the output current I2 of cyclic variation current source G2.Electrode E1 and E2 are corresponding to corresponding capacitor C1 of Fig. 3 a and C2.Guard electrode E3 is connected to the output of operational amplifier A 0, so the voltage potential of the voltage potential of guard electrode E3 and sensing electrode E1 and E2 is basic identical.Guard electrode E3 can be set to the back side and the side around sensing electrode E1 and E2, therefore can only form electric capacity between the conductive body of non-contact switch front and sensing electrode E1 and E2.The operational amplifier A 1 and the A2 that note that Fig. 9 a resemble corresponding operational amplifier A 1 of Fig. 3 a and A2, and the resistor R 1 of Fig. 9 a resembles the resistor R 1 of Fig. 3 a, and the cyclic variation current source G1 of Fig. 9 a and G2 resemble Fig. 3 a corresponding cyclic variation current source G1 and G2.Therefore, on a set time of output cycle the output Vd of the difference amplifier A2 of (for example Shu Chu peak value), its just and/or the average absolute value of negative cycle or utilize between signal (if the output I2 of current source G2 is sinusoidal) that synchronous demodulation extracts from output and the electric capacity relevant ratio and have linear relationship to the electric capacity of being correlated with outer electrode E2 with central electrode E1.Difference amplifier A2 provides output signal Vd to switch deciding section 205, and switch deciding section 205 is according to signal Vd decision whether startup non-contact switch.For example, switch deciding section 205 can decide according to phase place, amplitude, mean value and/or any other suitable speciality of signal Vd.Selectively, switch deciding section 205 may need the phase place of desired signal Vd of specified quantity and/or the continuous detecting of amplitude before decision starts non-contact switch, perhaps satisfy some requirement.If electric current I 2 is sinusoidal, can in switch deciding section 205, introduce synchronous demodulator so, even make under high noise levels, also can obtain the rate of change of the electric capacity relevant pair electric capacity of being correlated with high accuracy with outer electrode E2 with central electrode E1.It should be noted that switch deciding section 205 may also need one or more signals to determine whether starting switch except that signal Vd.For example, switch deciding section 205 may need reference signal to decide the phase place of signal Vd.Switch deciding section 205 provides the logical signal 206 of representing its decision to switch output 207, realizes required switch motion.Please note, switch output 207 can utilize logic output (normally high or low), solid-state switch output and/or the dry contact output (normally open or closed) of any suitable quantity, with any on-off mode including, but not limited to pulse mode, moment mode, trigger folding mode or the like and realize.Switch output 207 can also be set to produce audio frequency and/or video output, thus the state of indicator cock.Because capacitance measurement circuit 902a need experience several cycles of the output I2 of cyclic variation current source G2 and reach stable, so in start-up period, start delay part 203 provides enabling signal 204 to switch deciding section 205, in case its starting switch unintentionally.When sensing electrode E1 and E2 are set to separate the input certain distance of operational amplifier A 0 and A1, can utilize biaxial cable or two isometric coaxial cables to protect lead from sensing electrode E1 and E2, be connected to the protective shielding of guard electrode E3 with the external conductor conduct, and keep and be connected to the essentially identical voltage potential of inner conductor of each sensing electrode E1 and E2, therefore can not introduce stray capacitance, and basic any other injurious effects introduced by lead of eliminating.

Fig. 9 b illustrates the second illustrative circuit equipment 900b of one group of non-contact switch, comprises cyclic variation current source G11-G1n, cyclic variation current source G2, operational amplifier A 0, capacitance measurement circuit 902a1-902an, start delay part 203, switch deciding section 205 and switch output 207.Note that among the capacitance measurement circuit 902a1-902an that combines with operational amplifier A 0 each resembles capacitance measurement circuit 902a (referring to Fig. 9 a), and corresponding to corresponding non-contact switch in this group non-contact switch.Particularly, the electrode E2 that is connected to the in-phase input end of operational amplifier A 0 corresponds to the public outer electrode of this group non-contact switch, and the electrode E3 that is connected to operational amplifier A 0 output corresponds to the public guard electrode of this group non-contact switch.Among the electrode E11-E1n each is corresponding to the central electrode of corresponding non-contact switch.And, the operational amplifier A 0 of Fig. 9 b resembles the operational amplifier A 0 of Fig. 3 b, the operational amplifier A 11-A1n of Fig. 9 b resembles the corresponding operational amplifier A 11-A1n of Fig. 3 b, the difference amplifier A21-A2n of Fig. 9 b resembles the corresponding difference amplifier A21-A2n of Fig. 3 b, the resistor R 11-R1n of Fig. 9 b resembles the corresponding resistor R 11-R1n of Fig. 3 b, the cyclic variation current source G2 of Fig. 9 b resembles the cyclic variation current source G2 of Fig. 3 b, and the cyclic variation current source G11-G1n of Fig. 9 b resembles the cyclic variation current source G11-G1n of Fig. 3 b.Difference amplifier A21-A2n provides corresponding output signal Vd1-Vdn to switch deciding section 205, and switch deciding section 205 is according to corresponding each switch of signal Vd1-Vdn decision when the startup.Switch deciding section 205 provides the logical signal 206 of representing its corresponding decision to switch output 207, realizes the switch motion that each switch is required.Please note, switch output 207 can utilize logic output (normally high or low), solid-state switch output and/or the dry contact output (normally open or closed) of any suitable quantity, with any suitable on-off mode including, but not limited to pulse mode, moment mode, trigger folding mode or the like and realize each switch.Switch output 207 can also be set to produce audio frequency and/or video output, thereby indicates the state of each switch.The start delay part 203 of Fig. 9 b resembles the start delay part 203 of Fig. 9 a, and the switch that each switch of circuit arrangement 900b (referring to Fig. 9 b) resembles circuit arrangement 900a basically (is worked a) referring to Fig. 9.

Figure 10 a illustrates the 3rd illustrative circuit equipment 1000a according to non-contact switch of the present invention.Shown in Figure 10 a, circuit arrangement 1000a comprises central electrode E1, outer electrode E2, guard electrode E3, start delay part 203, switch deciding section 205, switch output 207 and capacitance measurement circuit 1002a, and this capacitance measurement circuit 1002a comprises cyclic variation voltage source G1, operational amplifier A 0 and A1, resistor R 1 and R2 and the operational amplifier A 2 that is set to difference amplifier.The in-phase input end of operational amplifier A 0 and A1 is all driven by the output Vs of cyclic variation voltage source G1.Central electrode E1 is connected to the inverting terminal of operational amplifier A 1 at node 201, and outer electrode E2 is connected to the inverting terminal of operational amplifier A 0 at node 202.Note that sensing electrode E1 and E2 are corresponding to corresponding capacitor C1 of Fig. 4 a and C2.Guard electrode E3 is connected to the output of cyclic variation voltage source G1, and is therefore basic identical with the voltage potential of two sensing electrode E1 and E2.Guard electrode E3 can be set to the back side and the side around sensing electrode E1 and E2, makes to form electric capacity between the conductive body of non-contact switch front and sensing electrode E1 and E2.Please note, the operational amplifier A 0 of Figure 10 a and A1 resemble corresponding operational amplifier A 0 of Fig. 4 a and A1, the resistor R 1 of Figure 10 a resembles the resistor R 1 of Fig. 4 a, and the resistor R 2 of Figure 10 a resembles the resistor R 2 of Fig. 4 a, and the cyclic variation voltage source G1 of Figure 10 a resembles the cyclic variation voltage source G1 of Fig. 4 a.Therefore, the output Vd of difference amplifier A2 of (for example peak value of cycle) or its are just and/or the average absolute value of negative cycle or utilize signal (if the output Vs of voltage source G1 is sinusoidal) that synchronous demodulation extracts and (there is linear relationship in value between r1 * c1-r2 * c2) from output on a set time of output cycle, wherein r1 and r2 are the corresponding resistors of resistor R 1 and R2, and c1 and c2 are the corresponding capacitance that is associated with sensing electrode E1 and E2.Difference amplifier A2 provides output signal Vd to switch deciding section 205, and whether switch deciding section 205 determines starting switch according to signal Vd.For example, switch deciding section 205 can decide according to phase place, amplitude, mean value and/or any other suitable speciality of signal Vd.Selectively, switch deciding section 205 may need the phase place of desired signal Vd of specified quantity and/or the continuous detecting of amplitude before the decision starting switch, perhaps satisfy some requirement.If voltage Vs is sinusoidal, can in switch deciding section 205, comprise synchronous demodulator so, even make under high noise levels, also can obtain (r1 * c1-r2 * c2) the variation of value with high accuracy.It should be noted that switch deciding section 205 may also need one or more signals to determine whether starting switch except that signal Vd.For example, switch deciding section 205 may need reference signal to decide the phase place of output signal Vd.Switch deciding section 205 provides the logical signal 206 of representing its decision to switch output 207, realizes required switch motion.Please note, switch output 207 can utilize logic output (normally high or low), solid-state switch output and/or the dry contact output (normally open or closed) of any suitable quantity, with any on-off mode including, but not limited to pulse mode, moment mode, trigger folding mode or the like and realize.Switch output 207 can also be set to produce audio frequency and/or video output, thus the state of indicator cock.Because capacitance measurement circuit 1002a need experience several cycles of the output Vs of cyclic variation voltage source G1 and reach stable, so in start-up period, start delay part 203 provides enabling signal 204 to switch deciding section 205, in case its starting switch unintentionally.When sensing electrode E1 and E2 are set to separate the input certain distance of operational amplifier A 0 and A1, can utilize biaxial cable or two isometric coaxial cables to protect lead from sensing electrode E1 and E2, be connected to the protective shielding of guard electrode E3 with the external conductor conduct, and keep and be connected to the essentially identical voltage potential of inner conductor of each sensing electrode E1 and E2, therefore can not introduce stray capacitance, and basic any other injurious effects introduced by lead of eliminating.

Figure 10 b illustrates the 3rd illustrative circuit equipment 1000b of one group of non-contact switch, comprises cyclic variation voltage source G1, operational amplifier A 0, capacitance measurement circuit 1002a1-1002an, start delay part 203, switch deciding section 205 and switch output 207.Note that among the capacitance measurement circuit 1002a1-1002an that combines with operational amplifier A 0 each resembles capacitance measurement circuit 1002a (referring to Figure 10 a), and corresponding to corresponding non-contact switch in this group non-contact switch.Particularly, the electrode E2 that is connected to the inverting terminal of operational amplifier A 0 corresponds to the public outer electrode of this group non-contact switch, and the electrode E3 that is connected to the output Vs of voltage source G1 corresponds to the public guard electrode of this group non-contact switch.Among the electrode E11-E1n each is corresponding to the central electrode of corresponding non-contact switch.And, the operational amplifier A 0 of Figure 10 b resembles the operational amplifier A 0 of Fig. 4 b, the operational amplifier A 11-A1n of Figure 10 b resembles the corresponding operational amplifier A 11-A1n of Fig. 4 b, the difference amplifier A21-A2n of Figure 10 b resembles the corresponding difference amplifier A21-A2n of Fig. 4 b, the resistor R 2 of Figure 10 b resembles the resistor R 2 of Fig. 4 b, the resistor R 11-R1n of Figure 10 b resembles the corresponding resistor R 11-R1n of Fig. 4 b, and the cyclic variation voltage source G1 of Figure 10 b resembles the cyclic variation voltage source G1 of Fig. 4 b.Difference amplifier A21-A2n provides corresponding output signal Vd1-Vdn to switch deciding section 205, and switch deciding section 205 is according to corresponding each switch of signal Vd1-Vdn decision when the startup.Switch deciding section 205 provides the logical signal 206 of representing its corresponding decision to switch output 207, realizes the switch motion that each switch is required.Please note, switch output 207 can utilize logic output (normally high or low), solid-state switch output and/or the dry contact output (normally open or closed) of any suitable quantity, with any suitable on-off mode including, but not limited to pulse mode, moment mode, trigger folding mode or the like and realize each switch.Switch output 207 can also be set to produce audio frequency and/or video output, thereby indicates the state of each switch.The start delay part 203 of Figure 10 b resembles the start delay part 203 of Figure 10 a, and the switch that each switch of circuit arrangement 1000b (referring to Figure 10 b) resembles circuit arrangement 1000a (is worked a) referring to Figure 10.

After above-mentioned illustrative embodiment had been described, the embodiment of other selection or variation also can realize.For example, the enforcement of the circuit of each non-contact switch disclosed herein can scale up, thereby detects the approaching of bigger human body appendage or other conductive body (for example palm of staff).The foregoing description can also be adapted to pass through measurement electric capacity between each electrode in conductive body and sensing electrode array, utilize an above-mentioned capacitance measurement technology and the computer that utilizes suitable electronic circuit or suitably programming to come analysis result, detect the position or the displacement of conductive body (for example people's appendage).Note that outer electrode can be positioned at the front or the back of a central electrode or a group switching centre electrode according to concrete application, perhaps to its relative any other suitable position.And, although the present invention can utilize nextport hardware component NextPort to realize, but be appreciated that, realize that one or more functions required for the present invention can alternatively utilize microcontroller, microprocessor, digital signal processor, programmable logic array or any other suitable hardware and/or software, some that utilize hardware or software or they whole or in part make up and realize.

Those of ordinary skills are not breaking away under the situation of invention disclosed principle here, can measure and non-contact switch is further improved and variation is understandable above-mentioned linear capacitance.Therefore, the present invention should not regard as limitation, unless limited by the scope and spirit of additional claim.

Claims

1, a kind of device that is used to detect at least one first capacitor (C1) and the relative variation of the electric capacity of at least one second capacitor (C2), each of this at least one first capacitor (C1) and at least one second capacitor (C2) all has first end and second end, and this device comprises:

At least one power supply is used for producing at least one cycle output signal on the corresponding output end of at least one power supply output;

Circuit, comprise at least one operational amplifier (A0, A1) and at least one difference amplifier (A2), this circuit is coupled to first end of this at least one first capacitor and this at least one second capacitor, and second end of this at least one first capacitor and this at least one second capacitor is electrically connected to the common ground end simultaneously;

Wherein, first end that this at least one operational amplifier is configured to use negative feedback to make this at least one first capacitor and this at least one second capacitor keeps the basic voltage potential that equates with respect to this common ground end, and this at least one first capacitor and this at least one second capacitor respond this at least one power supply output and be recharged; With

Wherein, this at least one difference amplifier is used to provide at least one signal of telecommunication (Vd), and

Wherein at this at least one signal of telecommunication and specify the relation that has substantial linear between the arithmetic function, this appointment arithmetic function relevant for the capacity ratio of this at least one first capacitor and this at least one second capacitor and multiply by first invariant this at least one first capacitor electric capacity and multiply by one of difference between the electric capacity of this at least one second capacitor of factor.

2, according to the device of claim 1, wherein

This at least one power supply is cyclic variation voltage source (G1), is used for driving first resistor (R1) that is connected to this first capacitor at first node (101), and drives second resistor (R2) that is connected to this second capacitor at Section Point (102),

Wherein this at least one operational amplifier comprises first operational amplifier (A1),

Wherein be provided for the inverting terminal of this first operational amplifier, be provided for the in-phase input end of this first operational amplifier at the voltage potential of this Section Point at the voltage potential of this first node,

Wherein between the output of this first operational amplifier and this first node, connect the 3rd resistor (R3), thereby the feedback current (I3) that flows through the 3rd resistor makes at the voltage potential of this first node and keeps being substantially equal to voltage potential at this Section Point

Wherein the output that is provided for first differential input end of this difference amplifier and this first operational amplifier of the voltage potential on one of this first and second node be provided for this difference amplifier second differential input end and

Wherein under stable state, this signal of telecommunication that is provided by this difference amplifier is directly proportional basically with the signal of representative by value (c1/c2-r2/r1) electric current (I2) modulation, that flow through this second resistor, this electric current (I2) is a periodic function of time, wherein c1 is the electric capacity of this first capacitor, c2 is the electric capacity of this second capacitor, r1 is the resistance of this first resistor, and r2 is the resistance of this second resistor.

3,, wherein under stable state, on a set time of the cycle of this signal of telecommunication, there is the relation of substantial linear between this signal of telecommunication that provides by this difference amplifier and the value (c1/c2-r2/r1) according to the device of claim 2.

4, according to the device of claim 2, wherein under stable state, this signal of telecommunication that provides by this difference amplifier just and/or have the relation of substantial linear between the average absolute value of negative cycle and the value (c1/c2-r2/r1).

5, according to the device of claim 2, also comprise synchronous demodulator, wherein this cyclic variation voltage source be sinusoidal voltage source and wherein this synchronous demodulator be used for extracting the signal that is directly proportional basically with value (c1/c2-r2/r1) from this signal of telecommunication that this difference amplifier provides by synchronous demodulation.

6, according to the device of claim 1, wherein, this at least one power supply comprises:

Period 1 property variable-current source (G1) is used to provide first output current (I1) to give this first capacitor, this first capacitor first node (101) be connected to this period 1 property variable-current source and

Property second round variable-current source (G2) is used to provide second output current (I2) to give this second capacitor, and this second capacitor is connected to this property second round variable-current source at Section Point (102),

Wherein the amount of this first output current equal this second output current amount constant K doubly,

Wherein be provided for the inverting terminal of this first operational amplifier and be provided for the in-phase input end of this first operational amplifier at the voltage potential of this Section Point at the voltage potential of this first node,

Wherein between the output of this first operational amplifier and this first node, connect first resistor (R1), thereby the feedback current (I3) that flows through this first resistor makes at the voltage potential of this first node and keeps equaling substantially voltage potential at this Section Point

Wherein the output that is provided for first differential input end of this difference amplifier and this first operational amplifier at the voltage potential of one of this first and second node be provided for this difference amplifier second differential input end and

Wherein under stable state, this signal of telecommunication that is provided by this difference amplifier is directly proportional basically with the signal of representative by value (c1/c2-K) electric current (I2) modulation, that flow into this second capacitor, this electric current (I2) is a periodic function of time, wherein c1 is the electric capacity of this first capacitor, and c2 is the electric capacity of this second capacitor.

7,, wherein under stable state, on a set time of this signal of telecommunication cycle, there is the relation of substantial linear between this signal of telecommunication that provides by this difference amplifier and the value (c1/c2-K) according to the device of claim 6.

8, according to the device of claim 6, wherein under stable state, this signal of telecommunication that provides by this difference amplifier just and/or have the relation of substantial linear between the average absolute value of negative cycle and the value (c1/c2-K).

9, according to the device of claim 6, also comprise synchronous demodulator, wherein this first and second cyclic variations current source be corresponding sinusoidal current source and wherein this synchronous demodulator be used for extracting the signal that is directly proportional basically with value (c1/c2-K) from this signal of telecommunication that this difference amplifier provides by synchronous demodulation.

10, according to the device of claim 1,

Wherein this at least one operational amplifier comprise first and second operational amplifiers (A1, A0) and

Wherein, this at least one power supply is cyclic variation voltage source (G1), is used to provide output voltage (Vs) to give the in-phase input end of this first operational amplifier and the in-phase input end of this second operational amplifier,

Wherein output and this first capacitor at this first operational amplifier connects first resistor (R1) between first node (101),

Wherein be provided for the inverting terminal of this first operational amplifier at the voltage potential of this first node, thereby the feedback current (I1) that flows through this first resistor makes the voltage potential that is substantially equal to the output voltage of this cyclic variation voltage source in the voltage potential maintenance of this first node

Wherein output and this second capacitor at this second operational amplifier connects second resistor (R2) between Section Point (102),

Wherein be provided for the inverting terminal of this second operational amplifier at the voltage potential of this Section Point, thereby the feedback current (I2) that flows through this second resistor makes the voltage potential that is substantially equal to the output voltage of this cyclic variation voltage source in the voltage potential maintenance of this Section Point

Wherein the output of this first operational amplifier output that is provided for first differential input end of this difference amplifier and this second operational amplifier be provided for this difference amplifier second differential input end and

Wherein under stable state, (r1 * c1-r2 * c2) signal of the time-derivative of output voltage modulation, this cyclic variation voltage source is directly proportional this signal of telecommunication that is provided by this difference amplifier basically by value with representative, the output voltage of this cyclic variation voltage source is a periodic function of time, wherein c1 is the electric capacity of this first capacitor, c2 is the electric capacity of this second capacitor, r1 is that the resistance and the r2 of this first resistor is the resistance of this second resistor.

11, according to the device of claim 10, wherein under stable state, on a set time of this signal of telecommunication cycle, this signal of telecommunication that provides by this difference amplifier and the value (relation that has substantial linear between r1 * c1-r2 * c2).

12, according to the device of claim 10, wherein under stable state, this signal of telecommunication that provides by this difference amplifier just and/or the average absolute value of negative cycle and the value (relation that has substantial linear between r1 * c1-r2 * c2).

13, according to the device of claim 10, also comprise synchronous demodulator, wherein this cyclic variation voltage source be sinusoidal voltage source and wherein this synchronous demodulator be used for extracting and the value (signal of r1 * c1-r2 * c2) be directly proportional basically by this signal of telecommunication that synchronous demodulation provides from this difference amplifier.

14, according to the device of claim 1, wherein each of this at least one first capacitor is a capacitive transducer.

15, according to the device of claim 1, wherein each of this at least one second capacitor is a capacitive transducer.

16, according to the device of claim 1, wherein each of this at least one first capacitor is a capacitance type sensor.

17, according to the device of claim 1, wherein each of this at least one second capacitor is a capacitance type sensor.

18, according to the device of claim 1, wherein each of this at least one second capacitor is corresponding to the internal capacitance that is associated with one of first and second inputs of operational amplifier.

19, according to the device of claim 1, also comprise first and second sensing electrodes (E1, E2), wherein this first capacitor is formed near this first sensing electrode by people's appendage, wherein this second capacitor form near this second sensing electrode by this people's appendage and

Also comprise:

Switch deciding section (205), be used for according to this signal of telecommunication that provides by this difference amplifier produce first control signal (206) and

Switch output (207) is used to indicate a state condition in response to first control signal.

20, according to the device of claim 19, also comprise

Start delay part (203) is used to postpone this switch deciding section and produces this first control signal, is in steady state situations up to this device.

21, according to the device of claim 19, also comprise guard electrode (E3), wherein this guard electrode and this first and second sensing electrode electricity is isolated, wherein this guard electrode keep with the essentially identical voltage potential of this first and second sensing electrode and wherein this guard electrode be set to the back side and side around this first and second sensing electrode.

22, according to the device of claim 19, wherein this first sensing electrode is a central electrode, and this second sensing electrode is an outer electrode, and wherein this central electrode and this outer electrode separate, and is centered on by this outer electrode to small part.

23, according to the device of claim 19, the surface that also comprises vessel form, this container has substrate and edge, wherein each of this first and second sensing electrode all is arranged on the wherein one side on this surperficial two sides, wherein this first sensing electrode is arranged near the substrate of this container, and this second sensing electrode is arranged near the edge of this container.

24, according to the device of claim 1, wherein this at least one second capacitor is one that chooses in a plurality of second capacitors.

25, according to the device of claim 1, wherein this at least one first capacitor comprises one group of first capacitor (C11-C1n),

Wherein this at least one operational amplifier comprises a plurality of first operational amplifiers (A11-A1n), and each in these a plurality of first operational amplifiers is all organized in first capacitor corresponding one with this and is associated,

Wherein this at least one difference amplifier comprises a plurality of difference amplifiers (A21-A2n), and each in these a plurality of difference amplifiers is all organized in first capacitor corresponding one with this and is associated,

Wherein organize in first capacitor each in corresponding these a plurality of first operational amplifiers that are associated and use negative feedback, thereby make this organize that corresponding one and this second capacitor remain on the basic voltage potential that equates in first capacitor with this,

Wherein each in these a plurality of first operational amplifiers be used for providing directly or indirectly export to corresponding one input of these a plurality of difference amplifiers and

Wherein each in these a plurality of difference amplifiers is used for providing corresponding one of a plurality of signals of telecommunication (Vd1-Vdn), wherein has the relation of substantial linear between each corresponding signal of telecommunication and this are organized the appointment arithmetic function of the electric capacity of corresponding one and this second capacitor in first capacitor.

26, according to the device of claim 25, wherein this group first capacitor is one group that chooses in many group first capacitors.

27, according to the device of claim 25, wherein:

This at least one power supply is cyclic variation voltage source (G1), be used to drive a plurality of first resistors (R11-R1n), each first resistor in a plurality of first nodes corresponding one be connected to this and organize in first capacitor corresponding one, with drive second resistor (R2) that is connected to this second capacitor at Section Point

Wherein corresponding one voltage potential is provided for corresponding one inverting terminal in these a plurality of first operational amplifiers in these a plurality of first nodes, be provided for corresponding one in-phase input end in these a plurality of first operational amplifiers with voltage potential at this Section Point

Wherein in these a plurality of first operational amplifiers, connect in a plurality of the 3rd resistors (R31-R3n) corresponding one in corresponding one output and this a plurality of first nodes between corresponding one, thereby flow through corresponding one feedback current in these a plurality of the 3rd resistors and make voltage potential corresponding in these a plurality of first nodes keep being substantially equal to voltage potential at this Section Point

Wherein the voltage potential at this Section Point is provided for first corresponding one in these a plurality of difference amplifiers differential input end, with corresponding one output in these a plurality of first operational amplifiers be provided for second corresponding one in these a plurality of difference amplifiers differential input end and

Wherein under stable state, basically be directly proportional by corresponding value (c1/c2-r2/r1) signal modulation, that flow through the electric current of this second resistor with representative by corresponding this signal of telecommunication that provides in these a plurality of difference amplifiers, this electric current is a periodic function of time, wherein c1 is that this organizes electric capacity corresponding one in first capacitor, c2 is the electric capacity of this second capacitor, r1 is corresponding one resistance in these a plurality of first resistors, and r2 is the resistance of this second resistor.

28, according to the device of claim 27, wherein under stable state, there is the relation of substantial linear between this signal of telecommunication in these a plurality of difference amplifiers on the set time of corresponding this signal of telecommunication cycle that provides and the corresponding value (c1/c2-r2/r1).

29, according to the device of claim 27, wherein under stable state, in these a plurality of difference amplifiers corresponding this signal of telecommunication that provides just and/or have the relation of substantial linear between the average absolute value of negative cycle and the corresponding value (c1/c2-r2/r1).

30, according to the device of claim 27, wherein this cyclic variation voltage source is a sinusoidal voltage source, also comprise synchronous demodulator, it is used for by synchronous demodulation, from the signal that corresponding this signal of telecommunication that provides of these a plurality of difference amplifiers extracts with value (c1/c2-r2/r1) accordingly is directly proportional basically corresponding one.

31, according to the device of claim 25, this at least one power supply comprises:

A plurality of period 1 property variable-current sources (G11-G1n), each period 1 property variable-current source is used for providing first output current (I11-I1n) to organize corresponding one of first capacitor to this, this organize in first capacitor each in a plurality of first nodes corresponding one be connected in these period 1 property variable-current sources corresponding one and

Property second round variable-current source (G2) is used to provide second output current (I2) to give this second capacitor, and this second capacitor is connected to this property second round variable-current source at Section Point,

Wherein in these first output currents corresponding one amount equal this second output current amount corresponding constant K doubly,

Wherein in these a plurality of first operational amplifiers, connect in a plurality of first resistors (R11-R1n) corresponding one in corresponding one output and this a plurality of first nodes between corresponding one, thereby flow through corresponding one feedback current in these a plurality of first resistors and make voltage potential corresponding in these a plurality of first nodes keep being substantially equal to voltage potential at this Section Point

Wherein under stable state, basically be directly proportional by corresponding value (c1/c2-K) signal modulation, that flow into the electric current of this second capacitor with representative by corresponding this signal of telecommunication that provides in these a plurality of difference amplifiers, this electric current is a periodic function of time, wherein c1 is that this organizes electric capacity corresponding one in first capacitor and c2 is the electric capacity of this second capacitor.

32, according to the device of claim 31, wherein under stable state, there is the relation of substantial linear between this signal of telecommunication in these a plurality of difference amplifiers on the set time of corresponding this signal of telecommunication cycle that provides and the corresponding value (c1/c2-K).

33, according to the device of claim 31, wherein under stable state, in these a plurality of difference amplifiers corresponding this signal of telecommunication that provides just and/or have the relation of substantial linear between the average absolute value of negative cycle and the corresponding value (c1/c2-K).

34, according to the device of claim 31, also comprise synchronous demodulator, wherein these a plurality of period 1 property variable-current sources and property second round variable-current source be corresponding sinusoidal current source and wherein this synchronous demodulator be used for by synchronous demodulation from the signal that corresponding this signal of telecommunication that provides of these a plurality of difference amplifiers extracts with value (c1/c2-K) accordingly is directly proportional basically corresponding one.

35, according to the device of claim 25, wherein, this at least one operational amplifier also comprises: second operational amplifier (A0);

Wherein, this at least one power supply is cyclic variation voltage source (G1), is used to provide output voltage (Vs) to give the corresponding in-phase input end of these a plurality of first operational amplifiers and the in-phase input end of this second operational amplifier,

Wherein in these a plurality of first operational amplifiers corresponding one output and should group first capacitor in corresponding one in a plurality of first nodes, connect in a plurality of first resistors (R11-R1n) corresponding one between corresponding one,

Wherein corresponding one voltage potential is provided for corresponding one inverting terminal in these a plurality of first operational amplifiers in these a plurality of first nodes, thereby flow through corresponding one feedback current in these a plurality of first resistors and make voltage potential corresponding in these a plurality of first nodes keep being substantially equal to the voltage potential of the output voltage of this cyclic variation voltage source

Wherein output and this second capacitor at this second operational amplifier connects second resistor between Section Point,

Wherein be provided for the inverting terminal of this second operational amplifier at the voltage potential of Section Point, thereby the feedback current that flows through this second resistor makes the voltage potential that is substantially equal to the output voltage of this cyclic variation voltage source in the voltage potential maintenance of this Section Point

Wherein corresponding one output is provided for first corresponding one in these a plurality of difference amplifiers differential input end in these a plurality of first operational amplifiers, with the output of this second operational amplifier be provided for second corresponding one in these a plurality of difference amplifiers differential input end and

Wherein under stable state, (r1 * c1-r2 * c2) signal of the time-derivative of output voltage modulation, this cyclic variation voltage source is directly proportional basically by corresponding value with representative by corresponding this signal of telecommunication that provides in these a plurality of difference amplifiers, the output voltage of this cyclic variation voltage source is a periodic function of time, wherein c1 is that this organizes electric capacity corresponding one in first capacitor, c2 is the electric capacity of this second capacitor, r1 is that resistance and r2 corresponding in these a plurality of first resistors is the resistance of this second resistor.

36, according to the device of claim 35, wherein under stable state, this signal of telecommunication in these a plurality of difference amplifiers on the set time of corresponding this signal of telecommunication cycle that provides and the corresponding value (relation that has substantial linear between r1 * c1-r2 * c2).

37, according to the device of claim 35, wherein under stable state, in these a plurality of difference amplifiers corresponding this signal of telecommunication that provides just and/or the average absolute value of negative cycle and the corresponding value (relation that has substantial linear between r1 * c1-r2 * c2).

38, according to the device of claim 35, also comprise synchronous demodulator, wherein this cyclic variation voltage source be sinusoidal voltage source and wherein this synchronous demodulator be used for extracting and (the signal of r1 * c1-r2 * c2) be directly proportional basically corresponding one of value accordingly from corresponding this signal of telecommunication that provides of these a plurality of difference amplifiers by synchronous demodulation.

39, according to the device of claim 25, also comprise one group of first sensing electrode (E11-E1n) and second sensing electrode (E2), wherein each in this group first capacitor is organized in first sensing electrode at this by people's appendage and is formed near corresponding one, wherein this second capacitor form near this second sensing electrode by this people's appendage and

Also comprise:

Switch deciding section (205), be used for according to by corresponding this signal of telecommunication that provides of these a plurality of difference amplifiers produce in a plurality of first control signals (206) corresponding one and

Switch output (207) is used for indicating in response to corresponding one the corresponding state condition of these a plurality of first control signals.

40, according to the device of claim 39, also comprise

Start delay part (203) is used for postponing each that this switch deciding section produces these a plurality of first control signals, is in steady state situations up to this device.

41, according to the device of claim 39, also comprise guard electrode (E3), wherein this guard electrode and this are organized first sensing electrode and second sensing electrode electricity is isolated,

Wherein this guard electrode keep with this organize first sensing electrode and the essentially identical voltage potential of this second sensing electrode and

Wherein this guard electrode is set to organize around this back side and side of first sensing electrode and this second sensing electrode.

42, according to the device of claim 39, wherein in this group first sensing electrode corresponding one be in the group switching centre electrode corresponding one, this second sensing electrode be public outer electrode and

Wherein each in this group switching centre electrode and this public outer electrode separate, and center on to this public outer electrode of small part quilt.

43, according to the device of claim 39, also comprise the surface of containing many depressed areas, each depressed area is a container shapes, and each container has substrate and edge, wherein this second sensing electrode and this organize first sensing electrode each all be arranged on the wherein one side on this surperficial two sides and

Wherein each in this group first sensing electrode is arranged near the substrate corresponding in these containers, and this second sensing electrode is arranged near the edge of these containers.

44, according to the device of claim 25, also comprise one group of first sensing electrode, wherein each in this group first capacitor by conductive body this organize form near corresponding one in first sensing electrode and

Wherein these a plurality of signals of telecommunication that provided by these a plurality of difference amplifiers are indicated this conductive body approaching with respect to these first sensing electrodes.

45, according to the device of claim 25, also comprise one group of first sensing electrode, wherein each in this group first capacitor is organized in first sensing electrode at this by conductive body and is formed near corresponding one,

Wherein this group first sensing electrode be arranged with form array and

Wherein these a plurality of signals of telecommunication that provided by these a plurality of difference amplifiers are indicated position or the displacement of this conductive body with respect to these first sensing electrodes.

46, according to the device of claim 25, also comprise second sensing electrode, wherein this second capacitor is formed near this second sensing electrode by conductive body.

47, according to the device of claim 1, wherein each of this at least one first capacitor is corresponding to the internal capacitance that is associated with one of first and second inputs of operational amplifier.

48, according to the device of claim 1, also comprise sensing electrode, wherein first capacitor form near this sensing electrode by conductive body and

Wherein this signal of telecommunication that is provided by this difference amplifier is indicated this conductive body approaching with respect to this sensing electrode.

49, according to the device of claim 1, also comprise sensing electrode, wherein this second capacitor is formed near this sensing electrode by conductive body and this signal of telecommunication of wherein being provided by this difference amplifier is indicated this conductive body approaching with respect to this sensing electrode.

50, according to the device of claim 1, also comprise first and second sensing electrodes (E1, E2), wherein this first capacitor is formed near this first sensing electrode by conductive body, wherein this second capacitor form near this second sensing electrode by this conductive body and

Wherein this signal of telecommunication that is provided by this difference amplifier is indicated this conductive body approaching with respect to this first and second sensing electrode.

51, a kind of capacitance detecting device is used to produce at least one the approaching logical signal in response to conductive body, and this capacitance detecting device comprises:

At least one first sensing electrode, first electric capacity causes generation by this conductive body near at least one first sensing electrode at this;

Second sensing electrode, contiguous this at least one first sensing electrode of this second sensing electrode, second electric capacity causes generation by this conductive body near this second sensing electrode; With

Constitute and make this at least one first sensing electrode and this second sensing electrode keep the voltage potential that equates basically and detect the device of this first electric capacity with respect to the relative variation of this second electric capacity with respect to the common ground end,

Wherein this at least one logical signal indication surpasses the state condition of at least one preset threshold value in the relative variation of this first and second electric capacity.

52, according to the capacitance detecting device of claim 51, wherein each of this at least one first sensing electrode and this second sensing electrode is arranged on the wherein one side on two sides on a surface,

Wherein this surface comprises at least one depressed area, and each depressed area is a container shapes, and each container has substrate and edge,

Wherein this at least one first sensing electrode be arranged near the substrate of container of this at least one depressed area correspondence and

Wherein this second sensing electrode is arranged near the edge of each container.

53, according to the capacitance detecting device of claim 51, also comprise guard electrode, wherein this guard electrode and this at least one first sensing electrode and this second sensing electrode electricity are isolated,

Wherein this guard electrode be maintained at this at least one first sensing electrode and the essentially identical voltage potential of this second sensing electrode and

Wherein this guard electrode is set to small part around this at least one first sensing electrode and this second sensing electrode.

54, according to the capacitance detecting device of claim 51, wherein, this second sensing electrode is a conductive grid, and is set at before this at least one first sensing electrode.

55, a kind of device that is used for the electric capacity of Measurement of capacitor (C1) comprises:

Cyclic variation voltage source (G1) is used to provide in-phase input end that output voltage (Vs) gives operational amplifier (A1) and first differential input end of difference amplifier;

This operational amplifier provides output (V1) to second differential input end of this difference amplifier directly or indirectly;

Wherein, at the output of this operational amplifier and be connected with first resistor (R1) between an end of this capacitor on the first node (101), the other end of this capacitor connects the common ground end; And

Wherein, voltage potential on this first node is provided for the inverting terminal of this operational amplifier, and the feedback current (I1) that flows through this first resistor makes the voltage potential on this first node keep the voltage potential of the output voltage that is substantially equal to this cyclic variation voltage source; And

This difference amplifier provides the signal of telecommunication (Vd);

Wherein, under stable state, (r1 * c1) signal of the time-derivative of output voltage modulation, this cyclic variation voltage source is directly proportional this signal of telecommunication that is provided by this difference amplifier basically by value with representative, the time-derivative of the output voltage of this cyclic variation voltage source is a periodic function of time, wherein c1 is the electric capacity of this first capacitor, and r1 is the resistance of this first resistor.

56, according to the device of claim 55, wherein, under stable state, on a set time of the cycle of this signal of telecommunication, this signal of telecommunication that provides by this difference amplifier and the value (relation that has substantial linear between the r1 * c1).

57, according to the device of claim 55, wherein, under stable state, this signal of telecommunication that provides by this difference amplifier just and/or the average absolute value of negative cycle and the value (relation that has substantial linear between the r1 * c1).

58, according to the device of claim 55, also comprise synchronous demodulator, wherein this cyclic variation voltage source be sinusoidal voltage source and wherein this synchronous demodulator be used for by synchronous demodulation, this signal of telecommunication that provides from this difference amplifier extracts and the value (signal of r1 * c1) be directly proportional basically.