CN116642557A - Non-contact measuring sensor for liquid volume of container based on three-time measuring method - Google Patents

Non-contact measuring sensor for liquid volume of container based on three-time measuring method Download PDF

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Publication number
CN116642557A
CN116642557A CN202310485660.2A CN202310485660A CN116642557A CN 116642557 A CN116642557 A CN 116642557A CN 202310485660 A CN202310485660 A CN 202310485660A CN 116642557 A CN116642557 A CN 116642557A
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capacitance
liquid
container
measuring
measuring electrode
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孙滕谌
甘庆华
曾凡佑
王凯
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Beijing Tashan Technology Co ltd
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Beijing Tashan Technology Co ltd
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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
    • G01F23/266—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 measuring circuits therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F22/00—Methods or apparatus for measuring volume of fluids or fluent solid material, not otherwise provided for

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Thermal Sciences (AREA)
  • Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)

Abstract

The application relates to a non-contact measuring sensor for liquid volume of a container based on a three-time measuring method, which constructs liquid to ground distribution C by self capacitance or mutual capacitance of three-time measuring electrodes w And a series capacitor C a The first equation, the second equation and the third equation of the system of equations are utilized to provide the series capacitance C with the measurement influence a Eliminating primordial energy, and calculating to obtain liquid-to-ground distribution C capable of accurately reflecting liquid volume w To output liquid amount information without knowing C of two electrodes by structural configuration a The formed proportion relation is more suitable for most scenes, on the other hand, the measuring error caused by the isolation solid or air interval between the measuring electrode and the measured liquid is overcome, the dynamic change of the liquid level due to vibration, angle change, inflow and outflow, temperature change, boiling, grounding environment and other reasons is overcome, the continuous liquid level is required to be measured by the measuring system, and the ring is overcomeInterference caused by temperature and humidity changes.

Description

Non-contact measuring sensor for liquid volume of container based on three-time measuring method
Technical Field
The application relates to a non-contact measuring sensor for the liquid volume of a container based on a three-time measurement method.
Background
The existing method for measuring the liquid level in the container by using the capacitance measurement method can be divided into two types of contact measurement and non-contact measurement.
The contact type measurement (such as that an electrode stretches into the liquid to be contacted with the liquid or is contacted with the liquid level through a film wrapped on the outer side of the electrode) mainly adopts to measure the capacitance of two pairs of triangular electrodes, and calculates the continuous liquid level by calculating the proportion of the two capacitances, for example, the scheme of measuring the liquid level by adopting two triangular polar plates is disclosed in Chinese patent CN201510602838.2, CN201910793969.1 and the like, and the measuring mode is easy to cause pollution because the detection end needs to be contacted with the liquid.
Non-contact measurement basically adopts that a measuring electrode is arranged outside the container wall to realize non-contact with liquid, for example, the water level is detected in a food processor (such as a soymilk machine) disclosed in Jiuyang Chinese patent CN201720526032.4 by a capacitive sensing plate arranged on the outer side wall of a glass; in the range hood disclosed in the Fangtai Chinese patent CN202222064921.7, an electrode plate is arranged on the outer wall of an oil cup to prevent the electrode group from being directly placed in oil liquid so as to influence the performance and the service life of the electrode group; in an embodiment of the capacitive liquid level sensor disclosed in international patent WO2018175478A2, the electrode arrangement is placed in direct contact with the reservoir wall dielectric material or in contact through an air-dielectric interface. For non-contact measurement, the main problem is that due to the existence of solid and/or air gap between the measurement electrode and the liquid, the series capacitance C between the measurement electrode and the water body is introduced regardless of the measured self-capacitance or mutual capacitance a . In practical application, the distance of the gap is easily affected by vibration (such as motor vibration of household appliances such as soymilk machine) and repeated taking and placing of container (such as detachable water tank of household appliances), and the dielectric constant of the medium between the gap, especially air medium, is easily affected by environmental temperature and humidity variation, resulting in series capacitor C a Changes occur, thereby affecting the accuracy of the measurement. Thus is not in contact withThe core problem to be solved by continuous level measurement is how to eliminate C a Is (non-contact level measurement due to C) a The conventional comparative triangulation method will have a large error).
In many application scenarios, continuous measurement of liquid level is not needed, only segmented liquid level measurement (such as highest, lowest or intermediate liquid level control or alarm) is needed, and the prior art adopts a segmented capacitance method mostly, but due to C a And larger segmentation errors can easily occur. In other applications, such as for the layered measurement of mixed liquids with different specific gravities (e.g. range hoods with oil-water mixing), there is a need for defining the height of the interface, or for continuously measuring the height or volume of the liquid in different layers, and also due to C a And a large error in measurement.
Disclosure of Invention
The basic principle of measuring the continuous liquid level change in the container by using the method of measuring the capacitance is to calculate the distributed capacitance (self-capacitance) C formed by the water body in the container to the ground through measurement and calculation w ，C w Can reflect the volume of liquid in the container. Considering that the earth can be considered as an infinite polar plate, the change of the liquid side wall to the average distance formed by the liquid level rise of the fixed container to the earth is negligible, for a container with invariable circumference, the liquid bottom area is invariable with the top area, the variable area of the liquid is proportional to the height of the liquid level, and C w Proportional to the surface area of the liquid and thus to the height of the liquid, whereas for containers of varying circumference, after the container is formed and fixed, the volume of liquid in the container and the height of the liquid level also form a fixed mapping relationship, and thus, can be determined by C w And obtaining liquid level information through conversion. For dynamic fluctuation of liquid level due to mechanical vibration, boiling, water inlet or outlet, inclination and the like, so that accurate liquid level cannot be defined, many application scenes usually need to obtain accurate liquid volume (such as an automobile oil tank in running), and C is a factor w In proportion to the surface area of the liquid, the fluctuation of the surface area is very small under the condition of liquid fluctuation, so that C is calculated by measuring w And is also critical to eliminate the effects of liquid fluctuations on continuous liquid measurements. Having radicalsThe object of the application is to eliminate the gap C by three non-contact measurements of the liquid volume in the container a Thereby obtaining C capable of accurately reflecting the liquid volume w By C w Eliminating the influence of liquid level fluctuation on continuous liquid measurement.
For this purpose, a non-contact measuring sensor for the liquid volume of a container based on a three-time measurement method is provided, which comprises a capacitance digital conversion circuit (CDC), a processing module, a first measuring electrode and a second measuring electrode; the first measuring electrode and the second measuring electrode are arranged outside the container wall and are not in contact with the liquid.
The capacitance-to-digital conversion circuit couples the respective measurement electrodes and acquires a first capacitance configured as one of a first self-capacitance measurement value acquired through the first measurement electrode, a second self-capacitance measurement value acquired through the second measurement electrode, a third self-capacitance measurement value acquired through the first measurement electrode in parallel with the second measurement electrode, and a first mutual capacitance measurement value acquired through the first measurement electrode and the second measurement electrode, the second capacitance and the third capacitance being respectively configured as two of the remaining three.
The processing module constructs a liquid-to-ground distributed capacitance C based on a first capacitance w Constructing a liquid-to-ground distributed capacitance C based on the second capacitance by a first equation with the corresponding series capacitance as a variable w A second equation with the corresponding series capacitance as a variable, and constructing a liquid-to-ground distribution C based on the third capacitance w The corresponding third equation with serial capacitance as a variable calculates the liquid-to-ground distributed capacitance C by using an equation set consisting of the first equation, the second equation and the third equation w To output liquid amount information
In the application, the self capacitance or the mutual capacitance of the electrodes is measured three times, and both the self capacitance and the mutual capacitance are C w And C a Composition, thus each measurement can build up a C w And C a Is to series capacitance C by using the equation set consisting of three equations a Eliminating the primary element to construct a liquid-to-ground distributed capacitor C w With a first capacitor, a second capacitor,Monotonic function of the third capacitor, and then solving C by using the first capacitor, the second capacitor and the third capacitor obtained by three times of measurement w . In this method, the C of the two electrodes need not be known by structural configuration a The formed proportional relation k can be solved even if the proportional relation k is unknown, so the method is more suitable for most scenes, and due to the series capacitor C a Is eliminated, thus can eliminate C a Measurement errors caused by C w The characteristic of the liquid volume is accurately reflected, the problem that the continuous liquid level is required to be measured by a measuring system due to dynamic change of the liquid level caused by vibration, angle change, inflow and outflow, temperature change, boiling, grounding environment and the like is solved, and in addition, the environmental temperature and humidity change (the environmental temperature and humidity change affects C) a And in particular isolating the measurement errors caused by humidity variations in the solid or air space.
In the present application, the container may be configured such that the top surface area of the liquid carried by the container does not change with increasing height, i.e. the inner circumference of the container does not change with increasing height, such as a column (cylinder, rectangular column, etc.), in which case the bottom area and top area are unchanged during the liquid rising process, the variable area of the liquid is proportional to the height of the liquid level, and C w Proportional to the surface area and thus to the height of the liquid, so that the treatment module can be based on C w Proportional relationship with liquid level by C w The level of the liquid is converted. In the present application, the liquid can be configured such that the top surface area of the liquid carried by the container changes with the rise of the height, i.e. the inner circumference of the container changes with the rise of the height, such as a cone or other irregular shape, in which case, since the inner circumference corresponding to each height of the container is fixed after the container is fixed in shape, the liquid level can be obtained by conversion, for example, by calculating the mapping relationship between the inner circumference (or liquid volume) of the container and the height (the numerical value of the inner circumference (or liquid volume) corresponding to each height is established in the list), the mapping relationship is written in the processing module in advance, and the processing module calculates C w The liquid level information can be obtained by utilizing the conversion of the mapping relation.
As a kind ofIn the improvement, on the basis that the container is configured to ensure that the top surface area of the liquid carried by the container is unchanged along with the rise of the height, the first capacitor can be configured as a first self-capacitance measurement value, the second capacitor is configured as a second self-capacitance measurement value, the third capacitor is configured as a first mutual capacitance measurement value, and at the moment, the liquid is distributed to the ground capacitor C w Is further configured to:
wherein C is s1 Is a first capacitance, C s2 Is the second capacitance, C x For the third capacitance, k 1 0.9-1.1, k 2 The value is allowed for the error. In this scheme, the first capacitor is configured as self-capacitance, the second capacitor is configured as self-capacitance, the third capacitor is configured as mutual capacitance, and a more accurate measurement result is obtained by utilizing the self-capacitance and mutual capacitance conversion mode.
Alternatively, as another improvement, on the basis that the container is configured such that the top surface area of the liquid carried by the container does not change with the rise of the height, the first capacitance may be configured as a first self-capacitance measurement value, the second capacitance may be configured as a second self-capacitance measurement value, and the third capacitance may be configured as a third self-capacitance measurement value, where the liquid distributes the capacitance C to the ground w Is further configured to:
wherein C is s1 Is a first capacitance, C s2 Is the second capacitance, C s3 For the third capacitance, k 1 0.9-1.1, k 2 The value is allowed for the error. In this scheme, the first capacitor is configured as self-capacitance, the second capacitor is configured as self-capacitance, the third capacitor is configured as self-capacitance after the area change (combining two electrodes in parallel by an analog switch), and the three-time measurement mode of the area change of the self-capacitance is utilized to obtain more accuracyIs a measurement of (a).
In the application, the serial capacitances between the first measuring electrode and the second measuring electrode and the liquid are configured to be the same or different, and in specific implementation, the serial capacitances can be realized by configuring the normal projection areas of the first measuring electrode and the second measuring electrode corresponding to the liquid to be the same or different, and configuring the interval between the first measuring electrode and the liquid to be the same or different from the interval between the second measuring electrode and the liquid, in other words, the requirements on the arrangement relation of the electrodes are not high, so that more arrangement selectivity is obtained, and most scene requirements are met.
Preferably, the distance between the first measuring electrode and the second measuring electrode is more than 1mm and less than the maximum distance of the boundary of the container, so that the two electrodes can sense the temperature and humidity change in the same space, and the interference of large temperature and humidity difference at the two electrodes caused by the too far distance is avoided.
Preferably, the non-contact measuring sensor for liquid volume in the container of the present application may further comprise a plurality of measuring electrodes arranged along the height direction of the container, wherein the measuring electrodes in the upper and lower layers are respectively used as the first measuring electrode and the second measuring electrode, and the elimination of C can be achieved by using any two of the measuring electrodes a While the multi-layer structure (i.e. the segments) of the measuring electrode can be used for level stratification detection; or, on the basis of arranging a plurality of layers of measuring electrodes arranged along the height direction of the container, each layer comprises at least two measuring electrodes, the two measuring electrodes in each layer are respectively used as the first measuring electrode and the second measuring electrode, for example, the arrangement mode of double-row segmentation is adopted, wherein the segmentation is used for liquid level layering detection, and the double rows are used for respectively measuring continuous liquid levels for different layers by using the three-time measuring method. The liquid level layering detection mode is further configured to acquire the capacitance of each layer of measurement electrode by utilizing a capacitance-to-digital conversion circuit (CDC), and the processing module determines the liquid level demarcation position of the liquid based on the capacitance change between the two adjacent layers of measurement electrodes by utilizing the characteristic that the capacitance change between the upper layer of electrode and the lower layer of electrode at the liquid level demarcation position is larger. For example, in a range hood scenario, water and oil are mixed (water is below and oil is above), water and oilThe capacitance change between the electrodes below the boundary interface is smaller, the same applies to the capacitance change between the electrodes above the water-oil boundary interface and below the oil top surface, and the capacitance change amplitude of the two electrodes between the adjacent electrodes of the water-oil boundary interface is larger due to the change of the dielectric constant of the material, so that the boundary position of the liquid level can be identified by using the processing module.
In the application, the first measuring electrode and the second measuring electrode are arranged on the same side or different sides of the container wall. The first measuring electrode and the second measuring electrode are arranged outside the wall at the bottom, the middle or the top of the container.
Drawings
FIG. 1 shows a schematic diagram of the connection of a measurement electrode, a capacitance-to-digital conversion circuit and a processing module;
FIG. 2 shows a schematic diagram of single electrode self-capacitance;
FIG. 3 shows a schematic diagram of the mutual capacitance of two electrodes;
FIG. 4 shows a schematic diagram of a two electrode combined self-capacitance;
FIG. 5 shows a schematic view of a container in which the inner perimeter of the container does not change as the height increases;
FIG. 6 shows a schematic view of a container with the inner perimeter of the container varying with increasing height;
FIG. 7 shows a schematic diagram of the same normal projected area of two electrodes corresponding to a liquid;
FIG. 8 shows different schematic diagrams of normal projected areas of two electrodes corresponding to a liquid;
FIG. 9 shows the same spacing between the electrodes and the liquid;
FIG. 10 shows a schematic diagram of the difference in spacing between the two electrodes and the liquid;
FIG. 11 shows a schematic view of a multilayer measuring electrode arranged along the height of the container;
FIG. 12 shows a schematic diagram of two measurement electrodes contained in each layer;
FIG. 13 shows a schematic diagram of oil-water mixing detection;
FIG. 14 shows a schematic view of measuring electrodes disposed on the same side or different sides of a container wall;
fig. 15 shows a schematic view of the outside of the wall with the measuring electrode arranged at the bottom, middle or top of the container.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application.
The embodiment of the application provides a container liquid amount non-contact measuring sensor based on a three-time measuring method.
As shown in fig. 1, the sensor includes a capacitance-to-digital conversion circuit (CDC) 100, a processing module 200, a first measurement electrode 300, a second measurement electrode 400; the first measuring electrode 300 and the second measuring electrode 400 are arranged outside the wall of the container 500 and are not in contact with the liquid 600.
The capacitance-to-digital conversion circuit 100 couples the respective measurement electrodes and acquires a first capacitance, a second capacitance, and a third capacitance. The first capacitance is configured as one of a first self-capacitance measurement value obtained through the first measuring electrode 300, a second self-capacitance measurement value obtained through the second measuring electrode 400, a third self-capacitance measurement value obtained through the first measuring electrode 300 and the second measuring electrode 400 in parallel, and a first mutual capacitance measurement value obtained through the first measuring electrode 300 and the second measuring electrode 400, and the second capacitance and the third capacitance are respectively configured as two of the other three. As shown in fig. 2, 3 and 4, the measurement result C is obtained by the first self-capacitance measurement value obtained by the first measurement electrode 300 S1 And a series capacitor C a1 (series capacitance between the first measurement electrode 300 and the liquid), liquid-to-ground distributed capacitance C w The relation of (2) is thatSecond self-capacitance measurement value obtained by second measurement electrode 400, measurement result C S2 And a series capacitor C a2 (series capacitance between second measurement electrode and liquid), liquid-to-ground distributed capacitance C w The relation of (2) is->Analog switchK is closed, a third self-capacitance measurement value is obtained through the parallel connection of the first measurement electrode 300 and the second measurement electrode 400, and a measurement result C is obtained s3 And a series capacitor C a1 、C a2 Liquid-to-ground distributed capacitance C w The relation of (2) is->The analog switch K is closed, the first mutual capacitance measurement value obtained by the first measuring electrode 300 and the second measuring electrode 400 is +.>
The processing module 200 constructs a liquid-to-ground distributed capacitance C based on the first capacitance w Constructing a liquid-to-ground distributed capacitance C based on the second capacitance by a first equation with the corresponding series capacitance as a variable w A second equation with the corresponding series capacitance as a variable, and constructing a liquid-to-ground distribution C based on the third capacitance w The corresponding third equation with serial capacitance as a variable calculates the liquid-to-ground distributed capacitance C by using an equation set consisting of the first equation, the second equation and the third equation w To output liquid amount information.
In the application, the self capacitance or the mutual capacitance of the electrodes is measured three times, and the self capacitance or the mutual capacitance is respectively the liquid-to-ground distributed capacitance C w And a series capacitor C a Composition, thus each measurement can build up a liquid-to-ground distributed capacitance C w And a series capacitor C a Is to series capacitance C by using the equation set consisting of three equations a Eliminating the primary element to construct a liquid-to-ground distributed capacitor C w Monotonic functions of the first capacitor, the second capacitor and the third capacitor are used for solving the liquid-to-ground distributed capacitor C by using the first capacitor, the second capacitor and the third capacitor obtained by three times of measurement w . In the method, the series capacitance C of two electrodes is not required to be known through structural configuration a The formed proportional relation k can be solved even if the proportional relation k is unknown, so the method is more suitable for most scenes, and due to the series capacitor C a Is eliminated byTherefore, the series capacitance C can be eliminated a The resulting measurement error, at the same time, utilizes the liquid-to-ground distributed capacitance C w The characteristic of the liquid volume is accurately reflected, the problem that the continuous liquid level is required to be measured by a measuring system due to dynamic change of liquid level caused by vibration, angle change, inflow and outflow, temperature change, boiling, grounding environment and the like is solved, and in addition, the environment temperature and humidity change (the influence of the environment temperature and humidity change on the series capacitor C can be overcome a And in particular isolating the measurement errors caused by humidity variations in the solid or air space.
In the present application, as shown in FIG. 5, the container 500 may be configured such that the top surface area of the liquid 600 carried by the container is unchanged with the rise of the height, i.e. the inner circumference of the container 500 is unchanged with the rise of the height, such as a column (column, rectangular column, etc.), the bottom area is unchanged with the top area during the rise of the liquid 600, the variable area of the liquid 600 is proportional to the height of the liquid 600, and the liquid-to-ground capacitance C is equal to the bottom area w Proportional to the surface area and thus to the liquid height, so that the process module can distribute the capacitance C over the liquid w Proportional relation with liquid level, capacitance C is distributed through liquid to ground w The level of the liquid is converted.
In the present application, as shown in fig. 6, the container 500 may be further configured such that the top surface area of the liquid 600 carried by the container is changed with the rise of the height, that is, the inner circumference of the container 500 is changed with the rise of the height, such as a cone or other irregular shape, in which case, since the inner circumference corresponding to each height of the container 500 is fixed after the container 500 is fixed in shape, the liquid level may be obtained by conversion, for example, by calculating the mapping relationship between the inner circumference (or the liquid volume) of the container 500 and the height (the list establishes the value of the inner circumference (or the liquid volume) corresponding to each height), the mapping relationship is written in the processing module 200 in advance, and the processing module 200 calculates the liquid-to-ground distribution capacitance C w The liquid level information can be obtained by utilizing the conversion of the mapping relation.
As shown in fig. 2, 3 and 5, as a modification, the container 500 is configured to hold a liquid600 may be configured as a first self-capacitance measurement taken by the first measurement electrode 300, based on the fact that the top surface area of 600 does not change with increasing height, the measurement result is a series capacitance C a1 Capacitance C distributed with liquid to ground w Series capacitance of (2)The second capacitance is configured as a second self-capacitance measurement taken through the second measurement electrode 400, the measurement being the series capacitance C a2 Capacitance C distributed with liquid to ground w Series capacitance of->The third capacitance is configured as a first mutual capacitance measurement value obtained by the first measuring electrode 300 and the second measuring electrode 400, the measurement result isAt this time, the liquid-to-ground distributed capacitance C w Is further configured to:
wherein C is s1 Is a first capacitance, C s2 Is the second capacitance, C x For the third capacitance, k 1 0.9-1.1, k 2 Values are allowed for errors, for example + -5% of the result. In this scheme, the first capacitor is configured as self-capacitance, the second capacitor is configured as self-capacitance, the third capacitor is configured as mutual capacitance, and a more accurate measurement result is obtained by utilizing the self-capacitance and mutual capacitance conversion mode.
Alternatively, as shown in fig. 2, 4 and 5, as another improvement, the first capacitance may be configured as a first self-capacitance measurement value obtained by the first measurement electrode 300, where the measurement result is a series capacitance C, on the basis that the container 500 is configured such that the top surface area of the liquid 600 carried by the container does not change with the rise of height a1 With liquidsGround distributed capacitance C w Series capacitance of (2)The second capacitance is configured as a second self-capacitance measurement taken through the second measurement electrode 400, the measurement being the series capacitance C a2 Capacitance C distributed with liquid to ground w Series capacitance of->The third capacitance is configured to obtain a third self-capacitance measurement value via the first measurement electrode 300 in parallel with the second measurement electrode 400, the measurement result being a series capacitance C a1 、C a2 Capacitance C distributed with liquid to ground w Series capacitor->At this time, the liquid-to-ground distributed capacitance C w Is further configured to:
wherein C is s1 Is a first capacitance, C s2 Is the second capacitance, C s3 For the third capacitance, k 1 0.9-1.1, k 2 The value is allowed for the error. In this scheme, the first capacitor is configured as self-capacitance, the second capacitor is configured as self-capacitance, the third capacitor is configured as self-capacitance after the area change (two electrodes are combined by an analog switch to enable the two electrodes to be connected in parallel), and a more accurate measurement result is obtained by using the mode of three measurement modes of the area change of the self-capacitance.
In the present application, when the series capacitances between the first measurement electrode and the second measurement electrode and the liquid are configured to be the same or different, respectively, as shown in fig. 7 and 8, in a specific implementation, the series capacitance can be implemented by configuring the normal projection area S1 of the first measurement electrode 300 corresponding to the liquid 600 and the normal projection area S2 of the second measurement electrode 400 corresponding to the liquid 600 to be the same or different, and configuring the distance D1 between the first measurement electrode 300 and the liquid 600 and the distance D2 between the second measurement electrode 400 and the liquid 600 to be the same or different, as shown in fig. 9 and 10, in other words, the requirements on the arrangement relationship of the electrodes are not high, so that more arrangement selectivity is obtained and most of scene requirements are satisfied.
Preferably, as shown in fig. 1, the distance D between the first measuring electrode 300 and the second measuring electrode 400 is greater than 1mm and not greater than the maximum distance of the container boundary, so as to ensure that the two electrodes sense the temperature and humidity variation in the same space, and avoid the interference of large temperature and humidity difference at the two electrodes caused by the too far distance.
Preferably, as shown in fig. 11, the non-contact measuring sensor for liquid volume in the container of the present application may further comprise a plurality of measuring electrodes arranged along the height direction of the container 500, wherein the measuring electrodes of the upper and lower layers are respectively used as the first measuring electrode 300 and the second measuring electrode 400, and the above-mentioned series capacitance C can be eliminated by using any two of the measuring electrodes a While the multi-layer structure (i.e. the segments) of the measuring electrode can be used for level stratification detection; alternatively, as shown in fig. 12, on the basis of providing a plurality of measuring electrodes arranged along the height direction of the container 500, each layer includes at least two measuring electrodes, and the two measuring electrodes in each layer are respectively used as the first measuring electrode 300 and the second measuring electrode 400, for example, in a double-row segmented arrangement mode, wherein the segmentation is used for detecting the liquid level in a layered manner, and the double rows are used for measuring the continuous liquid level for different layers by using the three measuring methods respectively. The liquid level layering detection mode is further configured to acquire the capacitance of each layer of measurement electrode by using a capacitance-to-digital conversion circuit (CDC) 100, and the processing module 200 determines the liquid level demarcation position of the liquid based on the capacitance change between the adjacent two layers of measurement electrodes by using the characteristic that the capacitance change between the upper and lower layers of electrodes at the liquid level demarcation is large. For example, as shown in fig. 13, in the range hood scenario, water 700 and oil 800 are mixed (water 700 is above oil 800), the capacitance change between the electrodes of each layer below the water-oil interface is small, the same applies to the capacitance change between the electrodes of each layer above the water-oil interface to below the oil top surface, and between the adjacent two electrodes of the water-oil interface, becauseThe dielectric constant of the material is changed, the capacitance change amplitude of the material and the material is larger, and the processing module 200 can identify the boundary position of the liquid level.
In the present application, as shown in fig. 14, the first measuring electrode 300 and the second measuring electrode 400 are disposed on the same side or different sides of the wall of the container 500. As shown in fig. 15, the first measuring electrode 300 and the second measuring electrode 400 are disposed outside the wall of the bottom, middle or top of the container.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the scope of the present application, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solution of the present application without departing from the spirit and scope of the technical solution of the present application.

Claims (10)

1. A non-contact measuring sensor for the liquid volume of a container based on a three-time measurement method, which is characterized in that:
the device comprises a capacitance-to-digital conversion circuit, a processing module, a first measuring electrode and a second measuring electrode;
the first measuring electrode and the second measuring electrode are arranged outside the container wall and used for non-contact capacitive sensing of the liquid;
the capacitance-to-digital conversion circuit is coupled with each measuring electrode and acquires a first capacitance, a second capacitance and a third capacitance, wherein the first capacitance is one of a first self-capacitance measured value acquired through the first measuring electrode, a second self-capacitance measured value acquired through the second measuring electrode, a third self-capacitance measured value acquired through the first measuring electrode and the second measuring electrode in parallel, and a first mutual capacitance measured value acquired through the first measuring electrode and the second measuring electrode, and the second capacitance and the third capacitance are two of the other three respectively;
the processing module constructs a liquid-to-ground distributed capacitance C based on the first capacitance w Constructing a first equation with the corresponding series capacitance as a variable based on the second capacitanceCloth capacitor C w A second equation with the corresponding series capacitance as a variable, and constructing a liquid-to-ground distribution C based on the third capacitance w A third equation with the corresponding series capacitance as a variable, and calculating the liquid-to-ground distributed capacitance C by using an equation set consisting of the first equation, the second equation and the third equation w To output liquid amount information.
2. The container liquid amount non-contact measurement sensor according to claim 1, wherein:
the first capacitance is configured as a first self-capacitance measurement, the second capacitance is configured as a second self-capacitance measurement, and the third capacitance is configured as a first mutual capacitance measurement;
the container is configured such that the top surface area of the liquid it carries does not change as the height rises;
the liquid-to-ground distributed capacitance C w Is further configured asWherein C is s1 For the first capacitance, C s2 For the second capacitance, C x For the third capacitance, k 1 0.9-1.1, k 2 The value is allowed for the error.
3. The container liquid amount non-contact measurement sensor according to claim 1, wherein:
the first capacitance is configured as a first self-capacitance measurement, the second capacitance is configured as a second self-capacitance measurement, and the third capacitance is configured as a third self-capacitance measurement;
the container is configured such that the top surface area of the liquid it carries does not change as the height rises;
the liquid-to-ground distributed capacitance C w Is further configured asWherein C is s1 For the first capacitance, C s2 For the second capacitance, C s3 For the third capacitance, k 1 0.9-1.1, k 2 The value is allowed for the error.
4. A container liquid amount non-contact measuring sensor according to claim 2 or 3, characterized in that:
the processing module is based on the liquid-to-ground distributed capacitance C w And converting the liquid level of the liquid according to the proportional relation formed by the liquid level height.
5. The container liquid amount non-contact measurement sensor according to claim 1, wherein: the series capacitances between the first and second measuring electrodes and the liquid are configured to be the same or different, respectively.
6. The container liquid amount non-contact measurement sensor according to claim 1, wherein: the distance between the first and second measuring electrodes is configured to be > 1mm and less than the maximum distance of the container boundary.
7. The container liquid amount non-contact measurement sensor according to claim 1, wherein:
the container liquid amount non-contact measuring sensor is provided with a plurality of layers of measuring electrodes which are distributed along the height direction of the container;
the measuring electrodes of the upper layer and the lower layer are respectively used as the first measuring electrode and the second measuring electrode; or each layer comprises at least two measuring electrodes, and the two measuring electrodes in each layer are respectively used as the first measuring electrode and the second measuring electrode.
8. The container liquid amount non-contact measurement sensor according to claim 7, wherein:
the capacitance-to-digital conversion circuit acquires the capacitance of each layer of measuring electrode, and the processing module determines the liquid level demarcation position of the liquid based on the capacitance change between two adjacent layers of measuring electrodes.
9. The container liquid amount non-contact measurement sensor according to claim 1, wherein: the first measuring electrode and the second measuring electrode are arranged on the same side or different sides of the container wall.
10. The container liquid amount non-contact measurement sensor according to claim 1, wherein: the first measuring electrode and the second measuring electrode are arranged outside the wall at the bottom, the middle or the top of the container.
CN202310485660.2A 2023-04-28 2023-04-28 Non-contact measuring sensor for liquid volume of container based on three-time measuring method Pending CN116642557A (en)

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CN202310485660.2A CN116642557A (en) 2023-04-28 2023-04-28 Non-contact measuring sensor for liquid volume of container based on three-time measuring method

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