CN107518851B - Dish washing machine and liquid level detection device and liquid level detection method thereof - Google Patents
Dish washing machine and liquid level detection device and liquid level detection method thereof Download PDFInfo
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- CN107518851B CN107518851B CN201710653472.0A CN201710653472A CN107518851B CN 107518851 B CN107518851 B CN 107518851B CN 201710653472 A CN201710653472 A CN 201710653472A CN 107518851 B CN107518851 B CN 107518851B
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- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
- A47L15/00—Washing or rinsing machines for crockery or tableware
- A47L15/42—Details
- A47L15/4244—Water-level measuring or regulating arrangements
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- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
- A47L2401/00—Automatic detection in controlling methods of washing or rinsing machines for crockery or tableware, e.g. information provided by sensors entered into controlling devices
- A47L2401/09—Water level
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Abstract
The invention discloses a dish washing machine and a liquid level detection device and a detection method thereof, wherein the liquid level detection device comprises an electrode module, a shielding module, a capacitance digital conversion module and a processing module, wherein the electrode module is arranged outside a container and comprises a liquid level sensing electrode pair and a reference liquid sensing electrode pair; the reference liquid sensing electrode pair comprises a reference liquid sensing electrode and a second grounding electrode; the shielding module comprises a first shielding electrode and a second shielding electrode; the capacitance digital conversion module respectively adopts differential potential drive to the liquid level sensing electrode and the first shielding electrode as well as to the reference liquid sensing electrode and the second shielding electrode, and obtains a liquid level sensing capacitor and a liquid level measurement unit capacitor; and the processing module calculates the liquid level height according to the liquid level sensing capacitor and the liquid level measurement unit capacitor. And a non-contact mode is adopted to avoid pollution, a shielding electrode is added to perform anti-phase compensation measurement, and external interference is avoided.
Description
Technical Field
The invention belongs to the technical field of electric appliance manufacturing, and particularly relates to a liquid level detection device of a dish washing machine, the dish washing machine with the liquid level detection device and a liquid level detection method of the dish washing machine.
Background
At present, there are several methods for measuring the level of liquid, for example, a capacitive water level monitoring method, in which two parallel electrodes are placed in water, one of the electrodes is rich in insulating layer, so that a capacitor C is formed between the two electrodes, and the capacity of the capacitor C is proportional to the depth of the electrodes submerged in water. However, there are problems with this detection method, for example, if it is used for a long time, scale is easily formed and the detection accuracy is lowered; the contact measurement is required to be fixed in the measured liquid, so that a water source is easily polluted; the traditional capacitance sensing technology is limited in stability and external interference (such as human hands), and usually causes capacitance value drift, so that the external interference resistance is poor, the EMI detection is not always qualified, and the requirement of CS (conducted interference rejection test) cannot be met.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.
Therefore, the present invention needs to provide a liquid level detection device, which can avoid the contamination to the liquid and improve the anti-interference capability when performing the liquid level detection.
The invention also discloses a dishwasher comprising the liquid level detection device and a liquid level detection method of the dishwasher.
In order to solve the above problem, a liquid level detecting apparatus according to an embodiment of a first aspect of the present invention includes: the electrode module is arranged outside the container and comprises a liquid level sensing electrode pair and a reference liquid sensing electrode pair, wherein the liquid level sensing electrode pair comprises a liquid level sensing electrode and a first grounding electrode, the liquid level sensing electrode and the first grounding electrode are correspondingly arranged in parallel, and the height of the liquid level sensing electrode in the liquid level change direction of the container is greater than or equal to the maximum allowable liquid level height; the reference liquid sensing electrode pair comprises a reference liquid sensing electrode and a second grounding electrode, and the reference liquid sensing electrode and the second grounding electrode are correspondingly arranged in parallel; the shielding module comprises a first shielding electrode and a second shielding electrode, the first shielding electrode is arranged corresponding to the liquid level sensing electrode pair and is positioned on one side of the liquid level sensing electrode pair far away from the liquid, and the second shielding electrode is arranged corresponding to the reference liquid sensing electrode pair and is positioned on one side of the reference liquid sensing electrode pair far away from the liquid; the capacitance digital conversion module is used for respectively adopting differential potential drive to the liquid level sensing electrode and the first shielding electrode as well as to the reference liquid sensing electrode and the second shielding electrode, obtaining a liquid level sensing capacitance according to a liquid level sensing signal acquired by the liquid level sensing electrode pair, and obtaining a liquid level measurement unit capacitance according to a liquid level measurement unit increment acquired by the reference liquid sensing electrode pair; and the processing module is used for calculating the liquid level height in the container according to the liquid level sensing capacitor and the liquid level measurement unit capacitor.
According to the liquid level detection device provided by the embodiment of the invention, the sensing electrode is arranged outside the container, non-contact measurement is adopted, the liquid can be prevented from being polluted, the sensing electrode is not easy to form scale, the measurement precision is ensured, in addition, the shielding electrode and the capacitance digital conversion module are additionally arranged to provide differential potential drive for the sensing electrode and the shielding electrode so as to carry out reverse phase compensation measurement, the external interference can be avoided, the detection precision and accuracy are improved, and the electromagnetic test performance is improved.
In some embodiments of the invention, the electrode module further comprises: an environment sensing electrode pair disposed outside the container at a position higher than the maximum allowable liquid level height, the environment sensing electrode pair including an environment sensing electrode and a third ground electrode, the environment sensing electrode and the third ground electrode being arranged in parallel correspondingly; the capacitance digital conversion module obtains an environment reference capacitance according to an environment sensing signal acquired by the environment sensing electrode pair, and the processing module calculates the liquid level height in the container according to the liquid level sensing capacitance, the liquid level measurement unit capacitance and the environment reference capacitance. So that the influence of the environment on the measurement can be compensated.
In some embodiments of the present invention, the first shielding electrode and the liquid level sensing electrode have the same size, and the second shielding electrode and the liquid level sensing electrode have the same size, so as to better shield external interference.
In some embodiments of the invention, the processing module performs gain compensation on the calculated liquid level height in the container, so that the measurement accuracy can be improved.
In some embodiments of the present invention, the liquid level sensing electrode, the reference liquid sensing electrode, the environment sensing electrode, the first shielding electrode, the second shielding electrode are all embedded on a flexible circuit board. Therefore, the device can be arranged outside containers with different shapes, and is more flexible and convenient.
In some embodiments of the invention, the liquid level detection apparatus further comprises: a connector module connected to the liquid level sensing electrode, the reference liquid sensing electrode, the environment sensing electrode, the first shielding electrode, the second shielding electrode, and the capacitance-to-digital conversion module, respectively.
In some embodiments of the invention, the distance between the liquid level sensing electrode pair and the first shield electrode is between 1/4-1/2 of the electrode width of the liquid level sensing electrode, and the distance between the reference liquid sensing electrode pair and the second shield electrode is between 1/4-1/2 of the electrode width of the reference liquid sensing electrode.
In some embodiments of the present invention, the capacitive-to-digital conversion module comprises a PDC1004 chip.
In some embodiments of the present invention, the PDC1004 chip employs a differential mode of CIN1, CIN2, CIN3, CIN4, where CIN1 is the liquid level sensing electrode input, CIN2 is the reference liquid sensing electrode input, CIN3 is the environmental sensing electrode input, CIN4 is floating, CIN1 and CIN2 are both in phase with SHLD1, CIN4 is in phase with SHLD2, the PDF1004 chip is configured to: MEAS1 ═ CNI1(CHA) -CIN4(CHB), where CIN1 is set as the positive phase input channel and CIN4 is set as the negative phase input channel; MEAS2 ═ CNI2(CHA) -CIN4(CHB), where CIN2 is set as the positive phase input channel and CIN4 is set as the negative phase input channel; wherein MEAS1 and MEAS2 are differential mode, CHA and CHB are channels.
Based on the liquid level detection device of the embodiment of the above aspect, the dishwasher of another embodiment of the invention comprises the liquid level detection device.
According to the dishwasher provided by the embodiment of the invention, by adopting the liquid level detection device in the embodiment of the aspect, liquid pollution can be avoided by adopting non-contact measurement, scale formation of the sensing electrode is avoided, the measurement precision is improved, and external interference can be reduced and the CS test or EMI test performance can be improved by adopting an anti-phase compensation measurement mode.
In order to solve the above problems, a liquid level detecting method of a dishwasher according to an embodiment of still another aspect of the present invention is a liquid level detecting method of a dishwasher, wherein the dishwasher includes a liquid level detecting device including an electrode module and a shielding module installed outside a container containing liquid, wherein the electrode module includes a liquid level sensing electrode pair including a liquid level sensing electrode and a first ground electrode, and a reference liquid sensing electrode pair, the liquid level sensing electrode pair being arranged in parallel to the first ground electrode and having a height in a liquid level variation direction of the container greater than or equal to a maximum allowable liquid level height; the reference liquid sensing electrode pair comprises a reference liquid sensing electrode and a second grounding electrode, and the reference liquid sensing electrode and the second grounding electrode are correspondingly arranged in parallel; the shielding module comprises a first shielding electrode and a second shielding electrode, the first shielding electrode is arranged corresponding to the liquid level sensing electrode pair and is positioned on one side of the liquid level sensing electrode pair far away from the liquid, and the second shielding electrode is arranged corresponding to the reference liquid sensing electrode pair and is positioned on one side of the reference liquid sensing electrode pair far away from the liquid; the liquid level detection method comprises the following steps: driving the liquid level sensing electrode, the reference liquid sensing electrode and the shielding module with differential potentials; acquiring a liquid level sensing capacitance according to the liquid level sensing signal acquired by the liquid level sensing electrode pair, and acquiring a liquid level measurement unit capacitance according to the liquid level measurement unit increment acquired by the reference liquid sensing electrode pair; and calculating the liquid level height in the container according to the liquid level sensing capacitor and the liquid level measurement unit capacitor.
According to the liquid level detection method of the dish washing machine, disclosed by the embodiment of the invention, liquid pollution can be avoided by adopting non-contact measurement, the sensing electrode is not easy to generate scale, the detection precision is ensured, the shielding electrode is additionally arranged, differential potential driving is carried out on the shielding electrode and the sensing electrode, the anti-phase compensation measurement is carried out, external interference can be avoided, and the anti-electromagnetic interference performance is improved.
In some embodiments of the present invention, the electrode module further comprises an environment sensing electrode pair disposed outside the container at a position higher than the maximum allowable liquid level height, the environment sensing electrode pair comprising an environment sensing electrode and a third ground electrode, the environment sensing electrode and the third ground electrode being arranged in parallel correspondingly; the liquid level detection method further comprises: obtaining an environment reference capacitance according to the environment sensing signals collected by the environment sensing electrode pairs; and calculating the liquid level height in the container according to the liquid level sensing capacitor, the liquid level measurement unit capacitor and the environment reference capacitor.
In some embodiments of the invention, the liquid level detection method further comprises: and performing gain compensation on the liquid level height in the container obtained by calculation.
In some embodiments of the present invention, the liquid level detection device comprises a PDC1004, the PDC1004 chip employs a differential mode of CIN1, CIN2, CIN3, CIN4, wherein CIN1 is a liquid level sensing electrode input, CIN2 is a reference liquid sensing electrode input, CIN3 is an environmental sensing electrode input, CIN4 is floating, CIN1 and CIN2 are both in phase with SHLD1, CIN4 is in phase with SHLD2, the PDF1004 chip is configured to: MEAS1 ═ CNI1(CHA) -CIN4(CHB), where CIN1 is set as the positive phase input channel and CIN4 is set as the negative phase input channel; MEAS2 ═ CNI2(CHA) -CIN4(CHB), where CIN2 is set as the positive phase input channel and CIN4 is set as the negative phase input channel; wherein MEAS1 and MEAS2 are differential mode, CHA and CHB are channels.
Drawings
FIG. 1 is a block diagram of a liquid level detection apparatus according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a sensing electrode mounting and dimensions according to one embodiment of the invention;
FIG. 3 is a schematic diagram of the principle of liquid level detection of a sensing electrode with the addition of a shield electrode according to one embodiment of the present invention;
FIG. 4 is a block diagram of a liquid level detection device according to one embodiment of the present invention;
FIGS. 5 (1) and (2) are schematic diagrams showing a circuit pattern of a conventional electrode with no interference from the outside, and FIG. 5 (3) is a schematic side view of a container and an electrode mounting;
FIG. 6 is a schematic diagram of a conventional equivalent circuit model for liquid level detection;
FIG. 7 is a schematic diagram of an equivalent circuit model for liquid level detection according to an embodiment of the present invention;
FIG. 8 is a schematic illustration of the stacking between anti-phase sense electrode plates according to one embodiment of the present invention;
FIG. 9 is a schematic diagram of dimensions of a shield electrode and a reference liquid sense electrode according to one embodiment of the invention;
FIG. 10 is a block diagram of a liquid level detection device according to one embodiment of the present invention;
FIG. 11 is a schematic view of a connector module according to one embodiment of the invention;
FIG. 12 is a block diagram of a dishwasher according to an embodiment of the present invention; and
FIG. 13 is a flow chart of a method of level detection for a dishwasher in accordance with an embodiment of the present invention.
Reference numerals:
a dishwasher 1000;
a liquid level detection device 100;
the electrode module 10, the shielding module 20, the capacitance-to-digital conversion module 30, the processing module 40 and the connector module 50;
a liquid level sensing electrode pair 11, a reference liquid sensing electrode pair 12, an environment sensing electrode pair 13;
liquid level sensing electrode 111, reference liquid sensing electrode 121, environment sensing electrode 131, first shielding electrode 21, second shielding electrode 22;
Cwfor the liquid capacitance to be measured, RwTo the liquid resistance to be measured, CpIs the capacitor capacitance.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
Hereinafter, a liquid level detection apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.
Fig. 1 is a block diagram of a liquid level detection apparatus according to an embodiment of the present invention, and as shown in fig. 1, the liquid level detection apparatus 100 of an embodiment of the present invention includes an electrode module 10, a shielding module 20, a capacitance-to-digital conversion module 30, and a processing module 40.
Wherein the electrode module 10 is installed outside the container, and the electrode module 10 includes a liquid level sensing electrode pair 11 and a reference liquid sensing electrode pair 12. Referring to fig. 2, which is a schematic size diagram of an electrode module according to an embodiment of the present invention, a liquid level sensing electrode pair 11 includes a liquid level sensing electrode 111 and a first ground electrode 112, the liquid level sensing electrode 111 and the first ground electrode 112 are correspondingly arranged in parallel and have a height in a liquid level variation direction of a container greater than or equal to a maximum allowable liquid level height, wherein the corresponding parallel arrangement may be consistent in size and arranged in parallel because the liquid level sensing electrode detects a liquid level height as h in fig. 2wProportional, the height of the level sensing electrode must therefore reach the maximum height allowed by the liquid level. The principle of operation of level height sensing is to measure the capacitance change between parallel plates, i.e. between the level sensing electrode 111 and the first ground electrode 112, as shown with reference to fig. 2 and 3, and in the direction of level change, e.g. Z-direction, the capacitance-electrolyte change is a proportional function of the level height as follows: cmeas ^ hwεw+(hL-hw)εaWherein Cmeas is the inter-plate capacitance hwIs the height of the liquid, hLIs the maximum height, epsilon, of liquid allowed in the containerwIs the dielectric constant of the liquid,. epsilonaIs the dielectric constant of air.
Referring to fig. 2, the reference liquid sensing electrode pair 12 includes a reference liquid sensing electrode 121 and a second ground electrode 122, the reference liquid sensing electrode 121 is disposed in parallel with the second ground electrode 122, and the reference liquid sensing electrode pair 12 is used to detect the increase of the liquid level measurement unit, preferably, the liquid level height to be measured must be higher than the height of the reference liquid sensing electrode 121 in order to make independent measurement of the liquid level height and temperature.
In the embodiment of the invention, the liquid level detection is carried out by adopting a non-contact capacitance sensing mode, the electrode module 10 is arranged outside the container, so that liquid pollution can be avoided, scale is not easily formed on the sensing electrode, and the detection precision is ensured.
The shielding module 20 includes a first shielding electrode 21 and a second shielding electrode 22, the first shielding electrode 21 is disposed corresponding to the liquid level sensing electrode pair 11 and located on a side of the liquid level sensing electrode pair 11 away from the liquid, and the second shielding electrode 22 is disposed corresponding to the reference liquid sensing electrode pair 12 and located on a side of the reference liquid sensing electrode pair 12 away from the liquid. As shown in fig. 3, the first shielding electrode 21 is disposed behind the liquid sensing electrode pair 11, so that the sensing of the liquid level sensing electrode 111 and the first ground electrode 112 has directionality, and thus external interference from the back side can be effectively prevented. Since the first shielding electrode 21 and the liquid level sensing electrode 111 have the same positive excitation signal driving, i.e. the same potential, and no electric field exists in the direction of the first shielding electrode 21, the region of effective induced capacitance change can only be one side of the container containing the liquid. Similarly, the second shielding electrode 22 also functions to shield interference on the backside of the reference liquid sensing electrode 121. In some embodiments of the present invention, in order to better shield the external interference, the first shielding electrode 21 is the same size as the liquid level sensing electrode 111, and the second shielding electrode 22 is the same size as the liquid level sensing electrode 111.
The capacitance-to-digital conversion module 30 is configured to drive the liquid level sensing electrode 111 and the first shielding electrode 21, and the reference liquid sensing electrode 121 and the second shielding electrode 22 by using differential potentials, that is, by using anti-phase compensation input signals, so that the parasitic capacitance can be kept constant, and a potential difference caused by a liquid level change can be avoided. The capacitance-to-digital conversion module 30 obtains a liquid level sensing capacitance according to the liquid level sensing signal collected by the liquid level sensing electrode pair 11, and obtains a liquid level measurement unit capacitance according to the increment of the collected liquid level measurement unit by the reference liquid sensing electrode 12. In some embodiments of the present invention, the capacitance-to-digital conversion module employs a PDC1004 chip.
The processing module 40 calculates the liquid level height within the container from the liquid level sensing capacitance and the liquid level measurement unit capacitance.
In some embodiments of the present invention, as shown in fig. 4, the electrode module 10 further includes an environment sensing electrode pair 13, the environment sensing electrode pair 13 is disposed at a position higher than the maximum allowable liquid level height outside the container, as shown in fig. 2, the environment sensing electrode pair 13 includes an environment sensing electrode 131 and a third grounding electrode 132, and the environment sensing electrode 131 and the third grounding electrode 132 are correspondingly arranged in parallel. For the characteristics of the container, in order to isolate the container from the liquid level to be measured, the environmental reference sensing electrode pair 13 needs to be placed above the maximum liquid level, i.e. only the environmental variation is tracked instead of the influence of the liquid in the container, and the environmental reference parameter obtained by using the environmental sensing electrode pair 13 can compensate the influence of the environmental variation, such as temperature, humidity or pressure on the container, on the measurement.
In embodiments of the present invention, the dimensions of the environmental sensing electrode 131 should be consistent with the dimensions of the reference liquid sensing electrode 111, so that the measurements can be subtracted and if the dimensions do not match, a differential measurement cannot be made because the amount of capacitance change is not linearly proportional to the size of the area between the parallel plates.
The capacitance-to-digital conversion module 30 obtains an environment reference capacitance according to the environment sensing signal collected by the environment sensing electrode pair 13, and the processing module 40 calculates the liquid level height in the container according to the liquid level sensing capacitance, the liquid level measurement unit capacitance and the environment reference capacitance.
Specifically, the liquid level sensing electrode 111, the reference liquid sensing electrode 121 and the environment sensing electrode 131 are driven by the same positive excitation signal, and the varying capacitance between the plates causes the positive excitation input signal to vary accordingly, so that the corresponding liquid level height variation can be calculated according to the corresponding variation relationship. Referring to the parametric illustration of FIG. 2, the processing module 40 calculates the arbitrary interval liquid level height according to the following formula:
wherein, Level is the height of liquid Level hRLFor reference liquid sensing electrode unit height (usually taken as 1), ClevelFor liquid level sensing capacitance, Clevel(0) The level sensing capacitance (empty state) when there is no liquid in the container, CRLFor measuring the unit capacitance of the liquid level, CREThe environment sensing capacitance. If the environmental impact is not taken into account, i.e. including the environmental sensing capacitance, C is used in the above formulaRL(0) To replace CRE，CRL(0) The specific capacitance is measured for the level detected by the reference liquid sensing electrode pair 12 when there is no liquid in the vessel.
Further, while theoretically the capacitance measurement is proportional to the liquid level height, in actual measurement there will be a large difference because the reference liquid sensing electrode 121 and the environment sensing electrode 131 are different for each layer of equally spaced liquid level sensing electrodes. Thus, in order to match the actual measured level height, in an embodiment of the invention, the processing module 40 performs a gain compensation on the calculated level height within the vessel. For example, a first order linear correction algorithm is applied to the calculated liquid level height in the container, and the formula of the first order linear correction algorithm is as follows: the Level' is the Level of the liquid Level after correction, the Gain is the Gain value, and the offset is the correction deviation, which can refer to the processing procedure of first-order linear correction in the related technology, and can perform real-time Gain compensation in each measurement to adapt to the change of the system environment state.
The following describes a process of driving the capacitance-to-digital conversion module 30, such as the PDC1004, by inverse phase compensation to avoid the potential difference caused by the parasitic capacitance according to the embodiment of the present invention.
First, a potential difference generated by a change in liquid level due to external disturbance will be described. Fig. 5 (1) and (2) are model top views showing the presence or absence of external interference of the conventional electrode. Fig. 5 (3) is a schematic side view of the container and sensing electrode mounting. Where CINx is the sense electrode, CwFor the liquid capacitance to be measured, RwTo the liquid resistance to be measured, CpFor the capacitor, as shown in (1) of fig. 5, if the system is isolated from external interference, the conventional method is to connect the liquid level sensing electrode 111 to the input end of the system, and then to cooperate with the first grounding electrode 112 for normal operationDo this. If any external interference with the ground is introduced, a parasitic capacitance C is generated as shown in (2) of fig. 5hTherefore, the measurement deviation of the capacitance is caused, and the deviation is very important enough to influence that the system cannot well distinguish the liquid level height change, reduce the accuracy and reliability of the system and finally influence the normal work of the whole system.
FIG. 6 is an equivalent circuit diagram of a motor model of a conventional liquid level height detecting system, wherein a liquid capacitor C to be detected can be simplified from a liquid level sensing electrode 111 to a first grounding electrode 112wLiquid resistance R to be measuredwCapacitor Cp. Wherein, the liquid capacitor C to be measuredwThe increase of the capacitance is linear change, when a human hand approaches or contacts the liquid to be measured, an additional parasitic capacitance C of the model is introducedhA potential difference due to the change in the liquid level is generated (without the approach or contact of a human hand). In the embodiment of the invention, the generation of the potential difference can be avoided by adopting an anti-phase compensation electrode model.
FIG. 7 is an equivalent circuit diagram of an electrode model of a liquid level height detection device according to an embodiment of the invention. The liquid level sensor can offset the parasitic capacitance generated when a human body approaches or contacts through symmetrical sensing electrode arrangement and anti-phase compensation driving, thereby carrying out stable liquid level measurement. In the traditional measuring method, the liquid to be measured can form potential change, and in the anti-phase compensation electrode model, the potential of the liquid to be measured can be always kept constant in positive and negative excitation driving through differential capacitance measurement. In the embodiment of the invention, the shielding electrode replaces the grounding electrode to access the forward driving signal, and the liquid level sensing electrode 111 and the first shielding electrode 21 adopt differential potential driving to enable the node CHThe potential of (2) remains fixed. As shown in fig. 7, where CINx represents the electrode input and SHLDy represents the shield electrode input, configured by the PDC1004 chip into differential mode (CINx and CINy), e.g., CIN1-CIN4, which is the default mode, SHLD1 (the first shield electrode) is in phase with CIN1, and SHLD2 (the second shield electrode) is in phase with CIN 4. Since CIN1 and CIN4 are 180 DEG opposite to each other, CHThe node maintains a constant potential.
FIG. 8 is a schematic diagram of an inter-electrode stack for reverse phase sensing according to an embodiment of the present invention, in which a shield electrode behind the electrodes is also included. The anti-phase drive signals are identical with respect to the capacitance of the liquid to be measured. The symmetry of the input measurement channel CHx, which represents the channel, including both channels CHA and CHB, and the shield electrode SHLD are critical. If the matching is not good, the liquid to be measured cannot keep constant potential.
In some embodiments of the present invention, the PDC1004 chip employs a differential mode of CIN1, CIN2, CIN3, CIN4, i.e., where there can be only two channels of electrode inputs at the same time, creating a differential mode, the following sensing combination collocation can be used to achieve anti-phase compensation measurements: CIN1 is the liquid level sensing electrode input, CIN2 is the reference liquid sensing electrode input, CIN3 is the environmental sensing electrode input (optional), CIN4 is floating, no additional electrodes, CIN1 and CIN2 are both in phase with SHLD1, CIN4 is in phase with SHLD2, i.e. CIN1 and CIN2 are 180 ° out of phase with CIN4, respectively. As shown in fig. 8, the SHLD corresponds to two channels, including SHLD1 and SHLD2, which correspond to channels CHA and CHB, respectively, and the SHLD2 adjacent to CHx needs to match the shield electrode of the other SHLD2 adjacent to SHLD1 for in-phase and anti-phase symmetric excitation input. The PDF1004 chip is configured to: MEAS1 ═ CNI1(CHA) -CIN4(CHB), where CIN1 is set as the positive phase input channel and CIN4 is set as the negative phase input channel; MEAS2 ═ CNI2(CHA) -CIN4(CHB), where CIN2 is set as the positive phase input channel and CIN4 is set as the negative phase input channel; wherein MEAS1 and MEAS2 are in differential mode. By adopting the reverse phase compensation measurement, the potential difference generated when the liquid level changes due to the existence of the parasitic capacitance can be avoided, so that the influence of external interference is avoided, and the EMI test and the CS test are more conveniently passed.
To improve the resolution and accuracy of the measurement, the sensing electrodes are arranged symmetrically, and further to improve the symmetry, referring to fig. 9, the shielding electrodes SHLD1 and SHLD2 (the ends away from the liquid) are strictly sized to the liquid level sensing electrode 111. Shield electrodes SHLD1 and SHLD2 are between liquid level sensing electrode 111 and reference liquid sensing electrode 121. Because the FDC1004 will sample the capacitance of each channel sequentially, when reading the capacitance measurement of the level sense electrode 111, the reference liquid sense electrode 121 is floating while the shield electrodes SHLD1 and SHLD2 are connected.
Also, in some embodiments of the present invention, the distance between liquid level sensing electrode pair 11 and first shield electrode 21 is between 1/4-1/2 of the electrode width of liquid level sensing electrode 111, and the distance between reference liquid sensing electrode pair 12 and second shield electrode 22 is between 1/4-1/2 of the electrode width of reference liquid sensing electrode 121. In addition, the resolution and accuracy of the measurement also depends on the gap between the sensing electrode and the container, the material and thickness of the container. The double-layer electrode plate, such as the insulation layer between the sensing electrode and the grounding electrode, can be selected from epoxy plates of FR 4. The liquid level measuring accuracy of the liquid level detecting device 100 of the embodiment of the invention can reach 1mm (millimeter).
In view of the different shapes of the containers, in some embodiments of the present invention, the liquid level sensing electrode 111, the reference liquid sensing electrode 121, the environment sensing electrode 131, the first shielding electrode 21, and the second shielding electrode 22 are all embedded on a flexible circuit board. As shown in fig. 10, the liquid level detection apparatus 100 further includes a connector module 50, and the connector module 50 is respectively connected to the liquid level sensing electrode 111, the reference liquid sensing electrode 121, the environment sensing electrode 131, the first shielding electrode 21, the second shielding electrode 22 and the capacitance-to-digital conversion module 30, as shown in fig. 11, which is a schematic diagram of the connector module according to an embodiment of the present invention, and the use of a soft-hard combination circuit allows the sensing electrode to be mounted on the surface of containers with various shapes, which is more flexible and convenient.
In summary, the liquid level detection apparatus 100 according to the embodiment of the present invention can avoid the problem of liquid contamination by installing the capacitance sensing electrode outside the container, and changing the relative node constant between the plates due to the liquid level change, so as to change the capacitance, and further determine the liquid level height according to the capacitance change, compared with placing the sensing electrode in the liquid; the non-contact installation measurement has an average effect, and scale cannot be formed to cause reduction of measurement precision; in addition, in the embodiment of the invention, the shielding electrode and the anti-phase compensation input signal circuit are added, so that the external interference can be effectively avoided, and the CS test performance and the EMI test performance are improved.
Based on the liquid level detection device of the above aspect embodiment, fig. 12 is a block diagram of a dishwasher according to an embodiment of the present invention, and as shown in fig. 12, a dishwasher 1000 of an embodiment of the present invention includes the liquid level detection device 100 of the above aspect embodiment, and the dishwasher 1000 includes a container for containing liquid and, of course, other necessary components, which will not be described in detail herein. The sensing electrode of the liquid level detection device 100 is placed outside the container, and a shielding electrode is disposed at an end away from the liquid, the sensing electrode and the shielding electrode of the liquid level detection device 100 are driven by differential potential to perform anti-phase compensation measurement, and the specific liquid level detection process refers to the description of the above embodiments, and is not repeated herein.
The dishwasher 1000 according to the embodiment of the present invention, by using the liquid level detection apparatus 100 according to the above-described embodiments, can avoid liquid contamination by using non-contact measurement, avoid scale formation on the sensing electrode, and improve measurement accuracy. And, the adoption of the anti-phase compensation measurement mode can reduce external interference and improve the CS test or EMI test performance.
Hereinafter, a liquid level detecting method of a dishwasher according to an embodiment of still another aspect of the present invention will be described with reference to the accompanying drawings. The dishwasher comprises a liquid level detection device, wherein the liquid level detection device comprises an electrode module and a shielding module which are arranged outside a container for containing liquid, the electrode module comprises a liquid level sensing electrode pair and a reference liquid sensing electrode pair, the liquid level sensing electrode pair comprises a liquid level sensing electrode and a first grounding electrode, the liquid level sensing electrode and the first grounding electrode are correspondingly arranged in parallel, and the height in the liquid level change direction of the container is greater than or equal to the maximum allowable liquid level height; the reference liquid sensing electrode pair comprises a reference liquid sensing electrode and a second grounding electrode, and the reference liquid sensing electrode and the second grounding electrode are correspondingly arranged in parallel; the shielding module comprises a first shielding electrode and a second shielding electrode, the first shielding electrode is arranged corresponding to the liquid level sensing electrode pair and is positioned on one side of the liquid level sensing electrode pair far away from the liquid, and the second shielding electrode is arranged corresponding to the reference liquid sensing electrode pair and is positioned on one side of the reference liquid sensing electrode pair far away from the liquid. The non-contact electrode arrangement is adopted, so that the liquid pollution can be avoided, and the electrodes are not easy to form scale, so that the detection precision is ensured.
Fig. 13 is a flowchart of a level detecting method of a dishwasher according to an embodiment of the present invention, as shown in fig. 13, the level detecting method of the embodiment of the present invention includes:
and S1, driving the liquid level sensing electrode, the reference liquid sensing electrode and the shielding module by adopting differential potential.
In the embodiment of the invention, the liquid level is measured by adopting the reverse phase compensation, so that the potential difference generated by the liquid level change caused by the parasitic capacitance introduced by the external interference is avoided, and the detection accuracy is improved.
In some embodiments of the present invention, the liquid level detection device comprises PDC1004, and PDC1004 chip employs differential mode of CIN1, CIN2, CIN3, CIN4, where CIN1 is the liquid level sensing electrode input, CIN2 is the reference liquid sensing electrode input, CIN3 is the environmental sensing electrode input, CIN4 is floating, CIN1 and CIN2 are both in phase with SHLD1, CIN4 is in phase with SHLD2, and PDF1004 chip is configured: MEAS1 ═ CNI1(CHA) -CIN4(CHB), where CIN1 is set as the positive phase input channel and CIN4 is set as the negative phase input channel; MEAS2 ═ CNI2(CHA) -CIN4(CHB), where CIN2 is set as the positive phase input channel and CIN4 is set as the negative phase input channel; wherein MEAS1 and MEAS2 are differential mode, CHA and CHB are channels. With this configuration, differential potential driving can be performed, providing an anti-phase compensation input signal.
And S2, acquiring a liquid level sensing capacitance according to the liquid level sensing signals acquired by the liquid level sensing electrode pairs, and acquiring a liquid level measurement unit capacitance according to the liquid level measurement unit increment acquired by the reference liquid sensing electrode pairs.
And S3, calculating the liquid level height in the container according to the liquid level sensing capacitance and the liquid level measurement unit capacitance.
In some embodiments of the invention, the electrode module further comprises an environment sensing electrode pair disposed outside the container at a position higher than the maximum allowable liquid level height, the environment sensing electrode pair comprising an environment sensing electrode and a third ground electrode, the environment sensing electrode being arranged in parallel with the third ground electrode.
In consideration of the influence of the environment on liquid level detection, the liquid level detection method provided by the embodiment of the invention can also obtain the environment reference capacitance according to the environment sensing signal acquired by the environment sensing electrode pair; and calculating a liquid level height within the container based on the liquid level sensing capacitance, the liquid level measurement unit capacitance, and the environmental reference capacitance, including environmental sensing that can compensate for environmental changes such as temperature, humidity, or pressure on the container effects on the measurement.
Further, in the embodiment of the invention, gain compensation is carried out on the liquid level height in the container obtained through calculation, and the measurement accuracy is improved.
In summary, the liquid level detection method of the dishwasher according to the embodiment of the present invention adopts non-contact measurement to avoid liquid contamination, the sensing electrode is not prone to scale generation, the detection precision is ensured, and the shielding electrode is added, and differential potential driving is performed on the shielding electrode and the sensing electrode to perform anti-phase compensation measurement, so that external interference can be avoided, and the anti-electromagnetic interference performance is improved.
It should be noted that in the description of this specification, any process or method description in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and that the scope of the preferred embodiments of the present invention includes additional implementations in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present invention.
The logic and/or steps represented in the flowcharts or otherwise described herein, e.g., an ordered listing of executable instructions that can be considered to implement logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.
It should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
It will be understood by those skilled in the art that all or part of the steps carried by the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, which may be stored in a computer readable storage medium, and when the program is executed, the program includes one or a combination of the steps of the method embodiments.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (12)
1. A liquid level detection device, comprising:
the electrode module is arranged outside the container and comprises a liquid level sensing electrode pair and a reference liquid sensing electrode pair, wherein the liquid level sensing electrode pair comprises a liquid level sensing electrode and a first grounding electrode, the liquid level sensing electrode and the first grounding electrode are correspondingly arranged in parallel, and the height of the liquid level sensing electrode in the liquid level change direction of the container is greater than or equal to the maximum allowable liquid level height; the reference liquid sensing electrode pair comprises a reference liquid sensing electrode and a second grounding electrode, and the reference liquid sensing electrode and the second grounding electrode are correspondingly arranged in parallel;
the shielding module comprises a first shielding electrode and a second shielding electrode, the first shielding electrode is arranged corresponding to the liquid level sensing electrode pair and is positioned on one side of the liquid level sensing electrode pair far away from the liquid, and the second shielding electrode is arranged corresponding to the reference liquid sensing electrode pair and is positioned on one side of the reference liquid sensing electrode pair far away from the liquid;
a capacitance digital conversion module, configured to drive the liquid level sensing electrode and the first shielding electrode, and the reference liquid sensing electrode and the second shielding electrode respectively by using differential potentials, so that a driving signal input to the liquid level sensing electrode and the first shielding electrode and a driving signal input to the reference liquid sensing electrode and the second shielding electrode are opposite to each other by 180 degrees, obtain a liquid level sensing capacitance according to the liquid level sensing signal acquired by the liquid level sensing electrode pair, and obtain a liquid level measurement unit capacitance according to a liquid level measurement unit increment acquired by the reference liquid sensing electrode pair;
and the processing module is used for calculating the liquid level height in the container according to the liquid level sensing capacitor and the liquid level measurement unit capacitor, and performing gain compensation on the liquid level height in the container by adopting a first-order linear correction algorithm on the calculated liquid level height in the container.
2. The fluid level detection apparatus of claim 1, wherein the electrode module further comprises:
an environment sensing electrode pair disposed outside the container at a position higher than the maximum allowable liquid level height, the environment sensing electrode pair including an environment sensing electrode and a third ground electrode, the environment sensing electrode and the third ground electrode being arranged in parallel correspondingly;
the capacitance digital conversion module obtains an environment reference capacitance according to an environment sensing signal acquired by the environment sensing electrode pair, and the processing module calculates the liquid level height in the container according to the liquid level sensing capacitance, the liquid level measurement unit capacitance and the environment reference capacitance.
3. The fluid level detection apparatus of claim 2, wherein the first shield electrode is of a size consistent with the fluid level sensing electrode and the second shield electrode is of a size consistent with the fluid level sensing electrode.
4. The fluid level detection apparatus of claim 3, wherein the fluid level sensing electrode, the reference fluid sensing electrode, the environment sensing electrode, the first shielding electrode, and the second shielding electrode are all embedded on a flexible circuit board.
5. The fluid level detection apparatus of claim 4, further comprising:
a connector module connected to the liquid level sensing electrode, the reference liquid sensing electrode, the environment sensing electrode, the first shielding electrode, the second shielding electrode, and the capacitance-to-digital conversion module, respectively.
6. The liquid level detection apparatus of claim 3, wherein a distance between the liquid level sensing electrode pair and the first shield electrode is between 1/4-1/2 of an electrode width of the liquid level sensing electrode, and a distance between the reference liquid sensing electrode pair and the second shield electrode is between 1/4-1/2 of an electrode width of the reference liquid sensing electrode.
7. The apparatus of claim 2, wherein the capacitance-to-digital conversion module comprises a PDC1004 chip.
8. The fluid level sensing apparatus of claim 7, wherein said PDC1004 chip employs a differential mode of CIN1, CIN2, CIN3, CIN4, wherein CIN1 is a fluid level sensing electrode input, CIN2 is a reference fluid sensing electrode input, CIN3 is an environmental sensing electrode input, CIN4 is floating, CIN1 and CIN2 are both in phase with SHLD1, CIN4 is in phase with SHLD2, said PDC1004 chip is configured to:
MEAS1 ═ CNI1(CHA) -CIN4(CHB), where CIN1 is set as the positive phase input channel and CIN4 is set as the negative phase input channel;
MEAS2 ═ CNI2(CHA) -CIN4(CHB), where CIN2 is set as the positive phase input channel and CIN4 is set as the negative phase input channel;
wherein MEAS1 and MEAS2 are differential mode, CHA and CHB are channels.
9. A dishwasher, comprising:
a dishwasher body including a container to hold a liquid; and
the liquid level detection apparatus of any one of claims 1-8.
10. A liquid level detection method of a dishwasher, the dishwasher comprising a liquid level detection apparatus including an electrode module and a shielding module installed outside a container containing liquid, wherein the electrode module includes a liquid level sensing electrode pair and a reference liquid sensing electrode pair, the liquid level sensing electrode pair includes a liquid level sensing electrode and a first ground electrode, the liquid level sensing electrode is arranged in parallel corresponding to the first ground electrode, and a height in a liquid level variation direction of the container is greater than or equal to a maximum allowable liquid level height; the reference liquid sensing electrode pair comprises a reference liquid sensing electrode and a second grounding electrode, and the reference liquid sensing electrode and the second grounding electrode are correspondingly arranged in parallel; the shielding module comprises a first shielding electrode and a second shielding electrode, the first shielding electrode is arranged corresponding to the liquid level sensing electrode pair and is positioned on one side of the liquid level sensing electrode pair far away from the liquid, and the second shielding electrode is arranged corresponding to the reference liquid sensing electrode pair and is positioned on one side of the reference liquid sensing electrode pair far away from the liquid; the liquid level detection method comprises the following steps:
driving the liquid level sensing electrode, the reference liquid sensing electrode and the shielding module by adopting differential potential, so that driving signals input into the liquid level sensing electrode and the first shielding electrode and driving signals input into the reference liquid sensing electrode and the second shielding electrode are opposite to each other by 180 degrees;
acquiring a liquid level sensing capacitance according to the liquid level sensing signal acquired by the liquid level sensing electrode pair, and acquiring a liquid level measurement unit capacitance according to the liquid level measurement unit increment acquired by the reference liquid sensing electrode pair;
and calculating the liquid level height in the container according to the liquid level sensing capacitor and the liquid level measurement unit capacitor, and performing gain compensation on the liquid level height in the container by adopting a first-order linear correction algorithm on the calculated liquid level height in the container.
11. The liquid level detection method of claim 10, wherein the electrode module further comprises an environmental sensing electrode pair disposed outside the vessel above the maximum allowable liquid level height, the environmental sensing electrode pair comprising an environmental sensing electrode and a third ground electrode, the environmental sensing electrode and the third ground electrode being arranged in parallel; the liquid level detection method further comprises:
obtaining an environment reference capacitance according to the environment sensing signals collected by the environment sensing electrode pairs;
and calculating the liquid level height in the container according to the liquid level sensing capacitor, the liquid level measurement unit capacitor and the environment reference capacitor.
12. The liquid level detection method of claim 11, wherein the liquid level detection apparatus comprises a PDC1004, and the PDC1004 chip employs a differential mode of CIN1, CIN2, CIN3, CIN4, wherein CIN1 is a liquid level sensing electrode input, CIN2 is a reference liquid sensing electrode input, CIN3 is an environmental sensing electrode input, CIN4 is floating, CIN1 and CIN2 are both in phase with SHLD1, CIN4 is in phase with SHLD2, the PDC1004 chip configured to:
MEAS1 ═ CNI1(CHA) -CIN4(CHB), where CIN1 is set as the positive phase input channel and CIN4 is set as the negative phase input channel;
MEAS2 ═ CNI2(CHA) -CIN4(CHB), where CIN2 is set as the positive phase input channel and CIN4 is set as the negative phase input channel;
wherein MEAS1 and MEAS2 are differential mode, CHA and CHB are channels.
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| CN108387294A (en) * | 2018-05-11 | 2018-08-10 | 广东美的厨房电器制造有限公司 | Water-level measuring equipment and its method, steam oven for water box |
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