CN101782418A - Non-contact capacitance liquid level meter - Google Patents
Non-contact capacitance liquid level meter Download PDFInfo
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- CN101782418A CN101782418A CN 201010122561 CN201010122561A CN101782418A CN 101782418 A CN101782418 A CN 101782418A CN 201010122561 CN201010122561 CN 201010122561 CN 201010122561 A CN201010122561 A CN 201010122561A CN 101782418 A CN101782418 A CN 101782418A
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- liquid level
- capacitive transducer
- sleeve pipe
- capacitance
- capacitor
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Abstract
The invention provides a non-contact high-precision capacitance liquid level meter, which is characterized in that: the non-contact high-precision capacitance liquid level meter comprises at least two capacitance sensors which are a first capacitance sensor and a second capacitance sensor, one ends of the first capacitance sensor and the second capacitance sensor are connected with a transmitter, the other ends thereof are respectively arranged in a first sleeve pipe and a second sleeve pipe of which the bottom parts are sealed, and the first sleeve pipe and the second sleeve pipe are stretched into a container. Due to the design of the capacitance liquid level meter, when a sensor is under the condition of stable dielectric medium constant of a medium which has high purity and is evenly distributed, an output capacitance is only relevant to the liquid level change between two sensors and the sleeve pipes and is irrelevant to other factors. A capacitance signal of the sensor is changed to a standard electrical signal by a transmitter and is transmitted by a signal cable remotely, thereby realizing no direct contact between the sensor and the medium and measuring liquid level by a non-contact way, and the measurement accuracy is high, the anti-interference ability is strong and the volume is small.
Description
Technical field
The present invention relates to a kind of non-contact capacitance liquid level meter, be used to measure the ultra-high purity medium liquid level.
Background technology
Ultra-high purity medium (gas, liquid chemical) is very extensive in the application of whole field of semiconductor manufacture, and the change of manufacturing process at present is more and more higher for the requirement of medium purity, and is also more and more higher for the measurement requirement of medium liquid level.Measuring liquid level generally adopts the metal capacitance liquid level gauge with the medium contact at present, has grown with the capacitance electrode time of liquid contact to tend to liquid is caused corrosion and osmosis pollution, thereby has influenced the purity of medium.
Summary of the invention
The purpose of this invention is to provide a kind of can the contact but the capacitance liquid level meter of the accurate measuring liquid level of energy with medium.
In order to achieve the above object, technical scheme of the present invention has provided a kind of contactless high-accuracy capacitor liquid level gauge, it is characterized in that, comprise at least two capacitive transducers, i.e. first capacitive transducer and second capacitive transducer, an end of first capacitive transducer and second capacitive transducer connects forwarder, and the other end is located at respectively in first sleeve pipe and second sleeve pipe of bottom sealing, first sleeve pipe and second sleeve pipe stretch in the container, and first capacitive transducer is as the measuring junction capacitor C
M, second capacitive transducer is as reference end capacitor C
R, by a fixing reference edge capacitor C
RDetect a measuring junction capacitor C
MRelative capacitance change Δ C
M=C
M-C
RWhen survey medium liquid level changes between first sleeve pipe and second sleeve pipe, be inserted in the variation that will produce electric capacity between first capacitive transducer in first sleeve pipe and second sleeve pipe and second capacitive transducer, the process transmitter carries out conversion process to the capacitance signal of first capacitive transducer and second capacitive transducer, get final product the electric signal of outputting standard, thereby accurately measure liquid level.
The present invention has used two capacitive transducers, a capacitive transducer measuring junction, another is then as the reference end, for sensor is not contacted with medium, two capacitive transducers insert respectively in the sleeve pipe, add that set collar then is the measuring-signal instability that causes for fear of because of the sensor shake.Subsequently, it is linear to draw the capacity output and the liquid level of sensor according to the electric capacity computing formula.Because the actual therein effect of only playing insulation of sleeve pipe can't cause the variation of electric capacity, so can not influence the variation of the electric capacity between the sensor.When survey medium liquid level changes between two sleeve pipes, be inserted in the variation that will produce electric capacity between the sensor in the sleeve pipe, the process transmitter carries out conversion process to the capacitance signal of sensor, gets final product the electric signal of outputting standard, thereby accurately measures liquid level.
Because the design of capacitance liquid level meter of the present invention, make sensor under the stable situation of medium dielectric constant, be the very high and dielectric distribution homogeneity of medium purity preferably the time, output capacitance only with two sensors and sleeve pipe between liquid level change the time relevant, irrelevant with other factors.By transmitter the capacitance signal of sensor is converted to the standard electric signal, by the signal cable teletransmission,, adopt the contactless measuring liquid level of coming so just can realize that sensor need not directly to contact with medium, and the accuracy of measuring is very high, and antijamming capability is strong and volume is small and exquisite.
Description of drawings
Fig. 1 is the structural representation of a kind of non-contact capacitance liquid level meter provided by the invention;
Fig. 2 is the circuit block diagram of transmitter among the present invention;
Fig. 3 is the equivalent circuit diagram of EMV interference protection measure among the present invention.
Embodiment
Specify the present invention below in conjunction with embodiment.
Embodiment
As shown in Figure 1, be the circuit block diagram of a kind of non-contact capacitance liquid level meter provided by the invention, comprise the first capacitive transducer D1 and the second capacitive transducer D2.The first capacitive transducer D1 and the second capacitive transducer D2 insert respectively in the first sleeve pipe T1 and the second sleeve pipe T2.Then vertical must the insertion in the container 1 in the first sleeve pipe T1 and the second sleeve pipe T2, the bottom sealing of the first sleeve pipe T1 and the second sleeve pipe T2, and insulate between the first sleeve pipe T1 and the second sleeve pipe T2.Fixing with first set collar 2 and second set collar 3 respectively of the first capacitive transducer D1 and the second capacitive transducer D2 and the first sleeve pipe T1 and second sleeve pipe T2 upper end.The first capacitive transducer D1 and the second capacitive transducer D2 connect transmitter 4 simultaneously.
The first capacitive transducer D1 is as measured capacitance C
M(measuring junction), the second capacitive transducer D2 is as the reference capacitor C
R(reference edge) is by a fixing reference capacitance C
RDetect a measured capacitance C
MRelative capacitance change Δ C
M=C
M-C
R(ε is the dielectric constant by electric capacity computing formula C=ε S/4 π kd, S is the area of capacitor plate, and k is the electrostatic force constant, and d is the distance between pole plate) in as can be seen when the area S of capacitor plate certain, between pole plate apart from d also one regularly, electric capacity is only relevant with dielectric constant ε.When measured medium changes between pole plate, be equivalent to dielectric constant ε and changing, thereby electric capacity also changes thereupon.Because the DIELECTRIC CONSTANT of liquid
1With the DIELECTRIC CONSTANT on the liquid level
2Difference, such as: ε
1＞ε
2, then when liquid level raise, dielectric constant values total between two electrodes strengthened thereupon, and electric capacity also increases; Otherwise when liquid level decline, the ε value reduces, and electric capacity also reduces.So, can come the height of measuring liquid level by the variation of two interelectrode electric capacitys.The sensitivity of electric capacity depends primarily on the difference of two kinds of specific inductive capacity, and, have only ε
1And ε
2Constantly could guarantee that level gauging is accurate.
According to formula, according to electric capacity computing formula C=ε S/4 π kd, ε is the dielectric constant, and S is the area of capacitor plate, and k is the electrostatic force constant, and d is the distance between pole plate.Therefrom as can be seen when the area S of capacitor plate certain, between pole plate apart from d also one regularly, electric capacity is only relevant with dielectric constant ε.Simultaneously, according to capacitive transducer output capacitance Cx=A+Bx, A, B are and capacitance structure size and the relevant constant of measured medium that the capacity output and the liquid level x that can obtain sensor are linear.Because the actual therein effect of only playing insulation of the first sleeve pipe T1 and the second sleeve pipe T2 can't cause the variation of electric capacity, so can not influence the variation of the electric capacity between the first capacitive transducer D1 and the second capacitive transducer D2.When survey medium liquid level changes between two sleeve pipes, be inserted in the variation that will produce electric capacity between the sensor in the sleeve pipe, capacitance signal through the 4 couples first capacitive transducer D1 of transmitter and the second capacitive transducer D2 carries out conversion process, get final product the electric signal of outputting standard, thereby accurately measure liquid level.
Thereby for can sensor acquisition to the electric capacity signal handle output electric standard signal, transmitter 4 comprises the reference oscillator of frequency adjustable as shown in Figure 2, the frequency of reference oscillator is passed through capacitor C
OSCAdjust, reference oscillator drives the integrator of at least two structure symmetries, be first integrator and second integral device, the number of integrator is identical with the number of capacitive transducer, first integrator and second integral device connect the described first capacitive transducer D1 and the second capacitive transducer D2 respectively, first integrator and second integral device connect signal processing circuit, and the amplitude of first integrator and second integral device is by the measuring junction capacitor C
MWith the reference edge capacitor C
RDecision, the signal that difference provided of first integrator and second integral device amplitude just reflects the measuring junction capacitor C
MWith the reference edge capacitor C
RDifference, the difference that is calculated this amplitude by signal processing circuit is adjusted to needed output voltage values subsequently.
Described signal processing circuit comprises subtraction circuit, the rear end of subtraction circuit connect successively source filter and adjustable amplifier, the difference of described first integrator and second integral device amplitude is filtered into dc power signal by active filter, delivers to adjustable amplifier then and adjusts to needed output voltage values.
If two measuring junction capacitor C
MWith the reference edge capacitor C
RBe worth identically, a d. c. voltage signal that obtains through overcommutation and filtering is exactly zero so.If measuring junction capacitor C
MChanged Δ C
M, the output voltage that obtains so is directly proportional with it.If two measuring junction capacitor C
MWith the reference edge capacitor C
RBe worth inequality, so as Δ C
M=0 o'clock, what obtain at output terminal was a bias, and it is superimposed upon on the d. c. voltage signal all the time.
In actual applications, also to consider the interference that site environment brings capacitance liquid level meter.Two sensors of capacitance liquid level meter equally are easy to be subjected to external high frequency interference with regard to image antenna, therefore need take measures to protect the input stage of high input impedance.Here the EMV interference protection measure of taking is difference resistance in series R on the described second capacitive transducer D2 and the first capacitive transducer D1
1And resistance R
2This resistance forms low-pass filter with stray capacitance (connecting the stray capacitance of drawing electric cable capacitance, electronic circuit of sensor and electronic circuit and the formed stray capacitances such as electric capacity of sensor internal polar plate and peripheral conductor formation) and transmitter internal capacitance (the transmitter internal capacitance is the electric capacity on the wiring board in the transmitter), has suppressed high-frequency interferencing signal.The value of resistance is:
K
1Be resistance R
1The voltage at two ends, I
CMFor passing through the measuring junction capacitor C
MElectric current, K
1Scope be 0.01～5V and
K
2Be resistance R
2The voltage at two ends, I
CRFor passing through the reference edge capacitor C
RElectric current, K
2Scope be 0.01～5V.
Claims (8)
1. contactless high-accuracy capacitor liquid level gauge, it is characterized in that, comprise at least two capacitive transducers, i.e. first capacitive transducer (D1) and second capacitive transducer (D2), one end of first capacitive transducer (D1) and second capacitive transducer (D2) connects forwarder (4), the other end is located at respectively in first sleeve pipe (T1) and second sleeve pipe (T2) of bottom sealing, first sleeve pipe (T1) and second sleeve pipe (T2) stretch in the container (1), and first capacitive transducer (D1) is as the measuring junction capacitor C
M, second capacitive transducer (D2) is as reference end capacitor C
R, by a fixing reference edge capacitor C
RDetect a measuring junction capacitor C
MRelative capacitance change Δ C
M=C
M-C
RWhen survey medium liquid level changes between first sleeve pipe (T1) and second sleeve pipe (T2), be inserted in the variation that will produce electric capacity between first capacitive transducer (D1) of first sleeve pipe (T1) and second sleeve pipe (T2) lining and second capacitive transducer (D2), process transmitter (4) carries out conversion process to the capacitance signal of first capacitive transducer (D1) and second capacitive transducer (D2), get final product the electric signal of outputting standard, thereby accurately measure liquid level.
2. a kind of contactless high-accuracy capacitor liquid level gauge according to claim 1 is characterized in that, is provided with first set collar (2) and second set collar (3) that is used for fixing capacitive transducer in the upper end of described first sleeve pipe (T1) and second sleeve pipe (T2).
3. a kind of non-contact capacitance liquid level meter according to claim 1 is characterized in that, the diameter of described first sensor (D1) and second sensor (D2) is 1～8000mm, and length is 5～50000mm.
4. a kind of non-contact capacitance liquid level meter according to claim 1 is characterized in that: be provided with on-the-spot Displaying Meter on described transmitter (4).
5. a kind of non-contact capacitance liquid level meter according to claim 1, it is characterized in that, described transmitter (4) comprises the reference oscillator of frequency adjustable, reference oscillator drives the integrator of at least two structure symmetries, be first integrator and second integral device, the number of integrator is identical with the number of capacitive transducer, first integrator and second integral device connect described first capacitive transducer (D1) and first capacitive transducer (D2) respectively, first integrator and second integral device connect signal processing circuit, and the amplitude of first integrator and second integral device is by the measuring junction capacitor C
MWith the reference edge capacitor C
RDecision, the signal that difference provided of first integrator and second integral device amplitude just reflects the measuring junction capacitor C
MWith the reference edge capacitor C
RDifference, the difference that is calculated this amplitude by signal processing circuit is adjusted to needed output voltage values subsequently.
6. a kind of non-contact capacitance liquid level meter according to claim 5, it is characterized in that, described signal processing circuit comprises subtraction circuit, the rear end of subtraction circuit connect successively source filter and adjustable amplifier, the difference of described first integrator and second integral device amplitude is filtered into dc power signal by active filter, delivers to adjustable amplifier then and adjusts to needed output voltage values.
7. a kind of non-contact capacitance liquid level meter according to claim 1 is characterized in that, goes up resistance in series R respectively at described second capacitive transducer (D2) and first capacitive transducer (D1)
1And resistance R
2, the value of resistance is:
With
Wherein, K
1Be resistance R
1The voltage at two ends, I
CMFor passing through the measuring junction capacitor C
MElectric current, K
2Be resistance R
2The voltage at two ends, I
CRFor passing through the reference edge capacitor C
RElectric current.
8. a kind of non-contact capacitance liquid level meter according to claim 6 is characterized in that K
1Scope be 1～5000mV, K
2Scope be 1～5000mV.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201010122561 CN101782418A (en) | 2010-03-11 | 2010-03-11 | Non-contact capacitance liquid level meter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201010122561 CN101782418A (en) | 2010-03-11 | 2010-03-11 | Non-contact capacitance liquid level meter |
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| Publication Number | Publication Date |
|---|---|
| CN101782418A true CN101782418A (en) | 2010-07-21 |
Family
ID=42522508
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 201010122561 Pending CN101782418A (en) | 2010-03-11 | 2010-03-11 | Non-contact capacitance liquid level meter |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102589646A (en) * | 2012-02-10 | 2012-07-18 | 梁支信 | U-shaped capacitive liquid level meter |
| CN102829841A (en) * | 2012-07-30 | 2012-12-19 | 新会康宇测控仪器仪表工程有限公司 | Capacitance liquid level transmitter |
| CN107440512A (en) * | 2017-08-18 | 2017-12-08 | 浙江绍兴苏泊尔生活电器有限公司 | Anti-overflow detection method and health preserving kettle |
| CN109839170A (en) * | 2017-11-29 | 2019-06-04 | 中国航发商用航空发动机有限责任公司 | Liquid level sensor |
| CN109900341A (en) * | 2019-04-15 | 2019-06-18 | 南京诺唯赞医疗科技有限公司 | A kind of fluid level detection system for in-vitro diagnosis equipment |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2093386U (en) * | 1991-04-08 | 1992-01-15 | 李德中 | Corrosion-resistant liquid level transducer |
| CN2112808U (en) * | 1992-01-23 | 1992-08-12 | 郑万生 | Electric field testing type material position device |
| CN101173863A (en) * | 2007-11-21 | 2008-05-07 | 黄樟焱 | Novel capacitance-type sensor |
| CN101458099A (en) * | 2008-12-20 | 2009-06-17 | 张学亮 | Capacitance type sensor |
-
2010
- 2010-03-11 CN CN 201010122561 patent/CN101782418A/en active Pending
Patent Citations (4)
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|---|---|---|---|---|
| CN2093386U (en) * | 1991-04-08 | 1992-01-15 | 李德中 | Corrosion-resistant liquid level transducer |
| CN2112808U (en) * | 1992-01-23 | 1992-08-12 | 郑万生 | Electric field testing type material position device |
| CN101173863A (en) * | 2007-11-21 | 2008-05-07 | 黄樟焱 | Novel capacitance-type sensor |
| CN101458099A (en) * | 2008-12-20 | 2009-06-17 | 张学亮 | Capacitance type sensor |
Non-Patent Citations (1)
| Title |
|---|
| 《电子测量技术》 20070630 王献峰等 基于CAV424的变压器油微水检测 186-188 5，6，8 第30卷, 第6期 * |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102589646A (en) * | 2012-02-10 | 2012-07-18 | 梁支信 | U-shaped capacitive liquid level meter |
| CN102589646B (en) * | 2012-02-10 | 2013-06-19 | 南宁测控自动化科技有限公司 | U-shaped capacitive liquid level gauge |
| CN102829841A (en) * | 2012-07-30 | 2012-12-19 | 新会康宇测控仪器仪表工程有限公司 | Capacitance liquid level transmitter |
| CN102829841B (en) * | 2012-07-30 | 2014-07-30 | 新会康宇测控仪器仪表工程有限公司 | Capacitance liquid level transmitter |
| CN107440512A (en) * | 2017-08-18 | 2017-12-08 | 浙江绍兴苏泊尔生活电器有限公司 | Anti-overflow detection method and health preserving kettle |
| CN109839170A (en) * | 2017-11-29 | 2019-06-04 | 中国航发商用航空发动机有限责任公司 | Liquid level sensor |
| CN109839170B (en) * | 2017-11-29 | 2021-04-23 | 中国航发商用航空发动机有限责任公司 | Liquid level sensor |
| CN109900341A (en) * | 2019-04-15 | 2019-06-18 | 南京诺唯赞医疗科技有限公司 | A kind of fluid level detection system for in-vitro diagnosis equipment |
| CN109900341B (en) * | 2019-04-15 | 2024-08-09 | 南京诺唯赞医疗科技有限公司 | Liquid level detection system for in-vitro diagnostic equipment |
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Owner name: SHANGHAI YIXIN ELECTRONICS TECHNOLOGY CO., LTD. SH Free format text: FORMER OWNER: SHANGHAI YIXIN ELECTRONICS TECHNOLOGY CO., LTD. SHANGHAI XINTONG SEMICONDUCTOR EQUIPMENT CO., LTD. |
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Effective date of registration: 20110608 Address after: 201108 No. 56 middle spring road, Xhenzhuang Industrial Zone, Shanghai Applicant after: Shanghai Zhengfan Technology Co., Ltd. Co-applicant after: Shanghai Yixin Electronic Technology Co., Ltd. Co-applicant after: Shanghai Zhengfan Semiconductor Equipment Co., Ltd. Address before: 201108 No. 56 middle spring road, Xhenzhuang Industrial Zone, Shanghai Applicant before: Shanghai Zhengfan Technology Co., Ltd. Co-applicant before: Shanghai Yixin Electronic Technology Co., Ltd. Co-applicant before: Shanghai Xintong Semiconductor Equipment Co., Ltd. |
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Effective date of registration: 20121015 Address after: 201108 No. 56 middle spring road, Xhenzhuang Industrial Zone, Shanghai Applicant after: Shanghai Zhengfan Technology Co., Ltd. Applicant after: Shanghai Zhengfan Semiconductor Equipment Co., Ltd. Address before: 201108 No. 56 middle spring road, Xhenzhuang Industrial Zone, Shanghai Applicant before: Shanghai Zhengfan Technology Co., Ltd. Applicant before: Shanghai Yixin Electronic Technology Co., Ltd. Applicant before: Shanghai Zhengfan Semiconductor Equipment Co., Ltd. |
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Application publication date: 20100721 |