CN105352565A - Differential-capacitor material level sensor - Google Patents
Differential-capacitor material level sensor Download PDFInfo
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- CN105352565A CN105352565A CN201510729454.7A CN201510729454A CN105352565A CN 105352565 A CN105352565 A CN 105352565A CN 201510729454 A CN201510729454 A CN 201510729454A CN 105352565 A CN105352565 A CN 105352565A
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- circuit
- sensor
- differential capacitance
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/26—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields
- G01F23/263—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors
Abstract
The present invention discloses a sensor (material level sensor) for realizing material level measurement by using differential capacitor measurement principles. The sensor comprises planar electrodes forming differential capacitors, a differential capacitor sensor dedicated circuit used for converting a differential capacitance signal into an electrical signal and carrying out signal processing, and a microprocessor used for setting the differential capacitor sensor dedicated circuit and for signal processing. Defects that a single-capacitor material level sensor is easy to be influenced by external factors such as temperature, humidity, ajacent-object coupling capacitance and electromagnetic interferences are overcome, and the differential-capacitor material level sensor has a strong anti-jamming capability and excellent long-term stability, and can be widely used for material level measurement of liquid-state and solid-state materials.
Description
Technical field
The present invention is a kind of capacitive transducer for material position measurement, the sensor (level sensor) of particularly a kind of material position measurement based on differential capacitance measuring principle.
Background technology
?in industrial automation and other multiple fields, need to detect position that is liquid in container or solid material.Electric capacity material position transducer (level sensor) based on capacitive measuring principle is one of sensor being widely used in level gauging.
Existing capacitance material level sensor causes single capacitor variation measuring method based on material position usually; but; sensor based on single capacitor measuring principle easily affects by various extraneous factor; as the temperature of measurement environment; humidity; the coupling capacitance of adjacent object, all can make the capacitance of single capacitor sensor change.Particularly in industrial production environment, because electromagnetic interference (EMI) is serious, single capacitor sensor is easily disturbed and occurs the situation of false triggering.Therefore, existing capacitance material level sensor also exists antijamming capability and the poor shortcoming of long-time stability, hinders the widespread use of capacitance material level level sensor in every field.
Summary of the invention
The shortcoming of prior art in view of the above, the object of the present invention is to provide a kind of electric capacity material position transducer (level sensor) overcoming above-mentioned shortcoming.
The present invention utilizes differential capacitance measuring principle to realize measuring the material position in container.The differential capacitance level sensor of such composition, the output of sensor is proportional to the difference (C1-C2) of 2 electric capacity instead of the value of single electric capacity C1 or C2.Due to extraneous factor, as temperature, humidity, the coupling capacitance of adjacent object, the impact of electromagnetic interference (EMI) on 2 adjacent electric capacity is the same, therefore, based on the output of the differential capacitance level sensor of differential capacitance measuring principle by the impact of extraneous factor much smaller than the impact of same factor on the level sensor based on single capacitor, there are stronger antijamming capability and good long-time stability, overcome the shortcoming that existing single-capacitor type level sensor is subject to extraneous factor impact.
Technical scheme of the present invention is as follows: the differential capacitance (C1-C2) that described sensor is made up of electric capacity C1 and electric capacity C2, differential capacitance sensor special circuit and microprocessor composition.As a preferred embodiment of the present invention, electric capacity C1, C2 are made up of plane electrode plate electric capacity, and 2 electrodes of composition electric capacity C1 are positioned at the front of circuit board, and the respective area of the reverse side of the circuit board of electric capacity C1 present position is applied copper by the circuit board of ground connection and covered.2 electrodes of composition electric capacity C2 are positioned at the reverse side of circuit board, and the respective area in the circuit board front of electric capacity C2 present position is applied copper by the circuit board of ground connection and covered.
As further technical scheme of the present invention, the differential capacitance C1-C2 be made up of plane electrode plate, converts electric signal to by differential capacitance sensor special circuit (ASIC), and can select to be input to microprocessor and be further processed.
As further technical scheme of the present invention, differential capacitance sensor special circuit (ASIC) in described sensor is by differential capacitance-voltage conversion circuit able to programme, zero correction circuit able to programme, pga circuit, bandwidth-limited circuit able to programme, temperature-compensation circuit+analog output buffer module, programmable comparator circuit, digital processing circuit+numeral exports driver module, disposable programmable OTP or multiple programmable eeprom memory, and I/O communication interface module forms.Each programmable parameter of special circuit can pass through interface communication module installation
.
As further technical scheme of the present invention, the zero point of sensor and sensitivity can by zero correction circuit able to programme and pga circuit adjustment.
As another kind of preferred version of the present invention, the zero point of sensor and sensitivity also can be regulated by external adjustable resistance.
As another kind of preferred version of the present invention, the functions such as the digital processing circuit of described special circuit has delayed able to programme, short-circuit protection function, programmable digital filter function, pulsewidth programmable pulse (Pulse) output circuit.
As another kind of preferred version of the present invention, programmable comparator circuit has programmable bound and programmable return difference.
As another kind of preferred version of the present invention, the analog-and digital-output of differential capacitance sensor special circuit can be connected to microprocessor and carry out further digital signal processing, the I/O mouth of microprocessor connects with the I/O mouth of differential capacitance sensor special circuit, arranges the parameter of differential capacitance sensor special circuit inside.
Accompanying drawing explanation
Fig. 1 is differential capacitance level sensor sensor of the present invention.
Fig. 2 is differential capacitance level sensor special circuit block diagram of the present invention.
Fig. 3 is differential capacitance level sensor system chart of the present invention.
Embodiment
Refer to accompanying drawing.It should be noted that, the diagram provided in the present embodiment only illustrates basic conception of the present invention in a schematic way, only the assembly relevant with the present invention is shown but not component count, shape and size when implementing according to reality is drawn in graphic, it is actual when implementing, and the kenel of each assembly, quantity and ratio can be a kind of change arbitrarily, and its assembly layout kenel also may be more complicated.
Be described in further detail the specific embodiment of the present invention below in conjunction with accompanying drawing, the present invention realizes as follows: as shown in Figure 1, utilizes the plate electrode on double-layer circuit board to form electric capacity C1 and C2.
Electric capacity C1 is positioned at the front of double-layer circuit board, and by 2 plane electrode plates, pole plate 1 and pole plate 2 form, and this electric capacity is used to respond to the material position in container.Its back side, namely the screen layer of copper as electric capacity C1 is applied by the circuit board of ground connection in the corresponding position of the reverse side of circuit board.
Electric capacity C2 is positioned at the reverse side of double-layer circuit board, and by 2 plane electrode plates, pole plate 3 and pole plate 4 form, and this electric capacity is used as reference capacitance, its back side, and namely the screen layer of copper as electric capacity C2 is applied by the circuit board of ground connection in corresponding position, the front of circuit board.
If employing multilayer circuit board, as 4 layer circuit boards, then the ground floor of circuit is as 2 pole plates of electric capacity C1, pole plate 1 and pole plate 2, the second layer ground connection (GND) of circuit board is as the screen layer of electric capacity C1, the third layer ground connection (GND) of circuit board as the screen layer of electric capacity C2, the 4th layer of 2 pole plates, pole plate 3 and pole plate 4 as electric capacity C2 of circuit board.
The shape of capacitor plate of the present invention is not limited to the shape shown in Fig. 1, the various plane capacitances be made up of other electrode shapes, as three-back-shaped plane capacitance, the plane capacitance of other shapes such as pectination plane capacitance also can as the electric capacity forming differential capacitance level sensor of the present invention.
as shown in Figure 1,the pole plate 1 of C1 is connected to just (+) input end of differential capacitance sensor special circuit, the pole plate 3 of electric capacity C2 is connected to negative (-) input end of differential capacitance sensor special circuit, the pole plate 2 of electric capacity C1 is connected with the pole plate 4 of electric capacity C2, as by C1, the public pole plate of the differential capacitance (C1-C2) of C2 composition, is connected to the common port (COMM) of differential capacitance sensor special circuit.
Fig. 2 is the block diagram for differential capacitance sensor special circuit (ASIC) of the present invention.Differential capacitance sensor special circuit (ASIC) is by differential capacitance-voltage conversion circuit able to programme, zero correction circuit able to programme, pga circuit, bandwidth-limited circuit able to programme, temperature-compensation circuit+analog output buffer module, programmable comparator circuit, digital processing circuit+numeral exports driver module, disposable programmable OTP or multiple programmable eeprom memory, I/O communication interface module forms.Each programmable parameter of special circuit can pass through interface communication module installation.As shown in Figure 2, at the zero point of special circuit, sensitivity, comparator threshold also can be arranged by external adjustable resistance.
Differential capacitance (C1-C2) converts electric signal to by differential capacitance sensor special circuit, and carries out signal transacting by circuit, exports analog signals Sout and on-off model Dout and pulse output signals Pulse.As shown in Figure 3, the output Sout of special circuit, Dout, Pulse also can select to be input to microprocessor and be further processed
.
When measuring material position, the front of the circuit board residing for C1 is affixed on is equipped with on the container of material
.when the material position in container changes, electric capacity C1 changes with the change of material position, and electric capacity C2 applies copper as screen layer owing to there being the circuit board of ground connection between C2 and material, thus insensitive to the change in location of material, thus, differential capacitance (C1-C2) is set to certain corresponding relation with material level.If sensor is by the interference of other extraneous factors, as electromagnetic interference (EMI), humidity changes, then because C1, C2 distance is very near, the impact of extraneous factor on electric capacity is the same, and therefore, differential capacitance (C1-C2) is not by the impact of other extraneous factors.
Differential capacitance (C1-C2) enters the adjustment module at zero point of special circuit after converting electric signal to by the differential capacitance-voltage conversion circuit able to programme in differential capacitance sensor special circuit of the present invention, when the material in container is empty, regulated or the adjustment module at zero point that arranged by microprocessor in ASIC circuit by external adjustable resistance, make the Sout of sensor be sensor predetermined zero point.When material raises gradually and arrives preposition, regulated by external adjustable resistance or transducer sensitivity module in ASIC circuit is set by microprocessor, making the output Sout of sensor reach predetermined sensitivity.Owing to regulating the sensitivity of sensor impact may be had on the zero point of sensor, above zero point, sensitivity setting up procedure can be repeated if desired, until zero point, till sensitivity all reaches predetermined value.
If senor operating temperature wider range, the temperature compensation module of the zero point in special circuit and sensitivity can be utilized to carry out temperature compensation to the zero point of sensor and sensitivity, to improve sensor work at different temperatures.
If need the output of switching value, after setting up Sout, can by external adjustable resistance or the programmable comparator threshold value being arranged special circuit by microprocessor, comparer is exported overturn, by the digital signal processing module in special circuit, filtering noise, meet the condition of certain pulsewidth in the output of comparer under, the output switching activity of digital output module Dout.To select the pulse exporting one fixed width at Pulse port if need pulse to export.
Due to extraneous factor, as temperature, humidity, electromagnetic interference (EMI), the impact on 2 adjacent equivalent capacitances of the coupling capacitance of external object is the same, again because the output of sensor of the present invention is correlated with the difference of electric capacity, C1-C2, instead of be correlated with the absolute value of electric capacity, therefore, differential capacitance Material Sensor of the present invention considerably reduces the impact of sensor by extraneous factor.
Comprehensively above-mentioned, the present invention utilizes the measuring method of differential capacitance, according to the differential capacitance temperature to external world of 2 adjacent electric capacity compositions, the change of humidity, the capacitance variations that electromagnetic interference (EMI) and other extraneous factors are brought is the principle of zero after subtracting each other, reduce the impact of extraneous factor on sensor, improve antijamming capability and the long-time stability of sensor.
Above-described embodiment is illustrative principle of the present invention and effect thereof only, but not for limiting the present invention.Any person skilled in the art scholar all without prejudice under spirit of the present invention and category, can modify above-described embodiment or changes.Therefore, such as have in art usually know the knowledgeable do not depart from complete under disclosed spirit and technological thought all equivalence modify or change, must be contained by claim of the present invention.
Claims (10)
1. one kind utilizes differential capacitance to realize the sensor measured the material position in container, it is characterized in that, sensor is by differential capacitance, differential capacitance sensor special circuit (ASIC) and microprocessor composition, differential capacitance is connected to the differential capacitance input end of differential capacitance sensor special circuit, the output of differential capacitance sensor special circuit can be connected to microprocessor and carry out further digital signal processing, the I/O mouth of microprocessor connects with the I/O mouth of differential capacitance sensor special circuit, the parameter of differential capacitance sensor special circuit inside is arranged.
2. differential capacitance sensor special circuit according to claim 1, it is characterized in that, differential capacitance sensor special circuit is by differential capacitance-voltage conversion circuit able to programme (C-V change-over circuit), zero correction circuit able to programme, pga circuit, programmable filter circuit, temperature-compensation circuit, programmable comparator circuit, digital processing circuit, the module compositions such as output buffer, the differential capacitance of induction material in container position is connected to differential capacitance-voltage conversion circuit, after converting electric signal to by differential capacitance-voltage conversion circuit, sequentially pass through zero correction circuit able to programme, pga circuit, programmable filter circuit, temperature-compensation circuit, programmable comparator circuit, digital processing circuit finally enters microprocessor and processes.
3. differential capacitance level sensor according to claim 1, it is characterized in that, the zero point of sensor and sensitivity can be adjusted by the zero correction circuit able to programme in special circuit and pga circuit, and the temperature coefficient of zero point and sensitivity can be compensated by the temperature compensation module of special circuit.
4. differential capacitance level sensor according to claim 1, is characterized in that, the zero point of sensor and sensitivity also can be regulated by external adjustable resistance.
5. differential capacitance level sensor according to claim 1, is characterized in that, the frequency response of sensor can be regulated by programmable bandpass filter.
6. differential capacitance level sensor according to claim 1, is characterized in that, digital processing circuit has delayed able to programme, short-circuit protection function, programmable digital filter function, exports programmable pulse function.
7. differential capacitance level sensor according to claim 1, is characterized in that, programmable comparator circuit has programmable bound and programmable return difference.
8. differential capacitance level sensor according to claim 1, is characterized in that, sensor setting, in the outer wall of container, when utilizing microprocessor or adjustable resistance material in a reservoir for sky, arranges the output zero point of sensor.
9. differential capacitance level sensor according to claim 1, is characterized in that, when material reaches preposition, is regulated the sensitivity of sensor, the sensitivity of sensor is met the demands by microprocessor or adjustable resistance.
10. differential capacitance level sensor according to claim 1, is characterized in that, when reaching preposition at material, by the threshold value of microprocessor or external adjustable resistance setting sensor sensor, return difference, output pulse width, makes the output of sensor meet predetermined requirement.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510729454.7A CN105352565A (en) | 2015-11-02 | 2015-11-02 | Differential-capacitor material level sensor |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510729454.7A CN105352565A (en) | 2015-11-02 | 2015-11-02 | Differential-capacitor material level sensor |
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| CN105352565A true CN105352565A (en) | 2016-02-24 |
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| CN201510729454.7A Pending CN105352565A (en) | 2015-11-02 | 2015-11-02 | Differential-capacitor material level sensor |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105920703A (en) * | 2016-05-19 | 2016-09-07 | 王卫东 | Infusion flow rate monitoring instrument |
| CN107870020A (en) * | 2017-12-26 | 2018-04-03 | 太原理工大学 | A kind of triaxial cable capacity water level measuring device |
| CN108692791A (en) * | 2018-03-30 | 2018-10-23 | 厦门乐人电子有限公司 | Liquid level detection device and liquid container |
| CN109690262A (en) * | 2016-08-17 | 2019-04-26 | Ksr Ip控股有限责任公司 | The capacitive character fluid levels level sensor of quick response |
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| CN201876293U (en) * | 2010-05-21 | 2011-06-22 | 董福贵 | Capacitance induction type material level detector |
| EP2348293A1 (en) * | 2009-12-01 | 2011-07-27 | Hirschmann Automotive GmbH | Method for capacitive measurement of fluid level and concentration of fluids |
| CN104748812A (en) * | 2015-03-28 | 2015-07-01 | 智恒（厦门）微电子有限公司 | Differential-capacitor type small article counting sensor |
| CN204575095U (en) * | 2015-05-11 | 2015-08-19 | 天津吉诺科技有限公司 | A kind of capacitive transducer with shield assembly |
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2015
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| US3950653A (en) * | 1975-01-24 | 1976-04-13 | Agridustrial Electronics, Inc. | Instrument for sensing level of granular materials |
| JPH05281254A (en) * | 1992-03-31 | 1993-10-29 | Fujikura Ltd | Semiconductor acceleration sensor |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105920703A (en) * | 2016-05-19 | 2016-09-07 | 王卫东 | Infusion flow rate monitoring instrument |
| CN105920703B (en) * | 2016-05-19 | 2022-06-03 | 中国人民解放军总医院 | Infusion flow monitor |
| CN109690262A (en) * | 2016-08-17 | 2019-04-26 | Ksr Ip控股有限责任公司 | The capacitive character fluid levels level sensor of quick response |
| CN109690262B (en) * | 2016-08-17 | 2021-02-26 | Ksr Ip控股有限责任公司 | Fast response capacitive fluid level sensor |
| CN107870020A (en) * | 2017-12-26 | 2018-04-03 | 太原理工大学 | A kind of triaxial cable capacity water level measuring device |
| CN107870020B (en) * | 2017-12-26 | 2019-12-17 | 太原理工大学 | Three coaxial cable capacitance type water level measuring device |
| CN108692791A (en) * | 2018-03-30 | 2018-10-23 | 厦门乐人电子有限公司 | Liquid level detection device and liquid container |
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