Non-conductive or conductive liquid level detection method and device, sensor and electric appliance
By forming a capacitor structure with a multivibrator driven by a DC power supply and a metal liquid level sensing probe, the liquid level is detected by the change in dielectric constant. This solves the problems of misjudgment and corrosion in the existing liquid level detection technology and realizes accurate detection of different water qualities and non-conductive liquids.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 王婕
- Filing Date
- 2024-10-21
- Publication Date
- 2026-04-21
AI Technical Summary
In the existing technology, electrode-type and capacitive liquid level detection methods are prone to misjudgment when detecting the liquid level of different water qualities, especially pure water and tap water. In addition, electrode probes are easily corroded, and capacitive detection is easily affected by temperature and cannot accurately detect non-conductive liquids such as liquid oils.
A multivibrator driven by a DC power supply is used to form a capacitor structure between a metal liquid level sensing probe and the container wall. The liquid level is detected by the change in dielectric constant, and a high-level or astable pulse signal is output. The liquid level height is identified by a computer.
It enables accurate level detection of water with different conductivity and non-conductive liquids, avoiding electrode corrosion and temperature effects, and is easy to install and low in cost.
Smart Images
Figure CN121898558A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sensor technology, and specifically to a method, apparatus, sensor, and electrical appliance for detecting non-conductive or conductive liquid levels. Background Technology
[0002] Currently, the mainstream methods for detecting the level of conductive liquids (usually water-containing liquids) in containers are traditional electrode and capacitive methods. For example, for water level detection in kettles, an electrode needle that is in direct contact with the water is installed inside the kettle. The conductivity of water is used for electrode-based water level detection. A certain low voltage is applied to the electrode probe, and then water with a certain resistance is passed through it. Through a voltage divider circuit, the change in voltage is detected, thereby determining whether there is water at a certain level in the kettle.
[0003] However, electrode-based detection has the following problems: 1. This method can lead to different detected voltage levels due to variations in water quality, conductivity, and equivalent resistance. For example, purified water has a higher resistance because it lacks minerals, impurities, or other electrolytes, resulting in very low conductivity or even theoretically no conductivity, thus producing a small current through the electrodes. In contrast, tap water, which contains many minerals, has a lower resistivity, leading to a larger current through the electrodes. Therefore, the same volume of water will produce different currents due to different water qualities, resulting in significant differences in the voltage detected by the voltage divider circuit, often leading to misjudgments and failure to detect correctly. 2. Since the electrode probe is installed inside the kettle and in direct contact with the water, prolonged use can cause corrosion due to electrolysis during measurement. Even stainless steel probes can rust and become coated with scale due to electrolysis, leading to malfunction. This can cause the electrode probe to lose conductivity or its conductivity to decrease, easily resulting in misjudgments and failure to detect correctly. To date, no probe-contact method has been found that can detect insulating liquids and greases (such as cooking oil).
[0004] Current capacitive detection methods are generally non-contact and tightly attached to the outside of the container, which is easily affected by temperature. For example, it may be inaccurate to detect liquids heated to very hot in a kettle. In addition, the constantly boiling and churning liquids and the steam evaporating from the kettle can also lead to misjudgments and failure to detect properly.
[0005] Therefore, there is an urgent need for a liquid level detection device that can effectively and accurately detect liquids of different qualities, such as pure water, purified water, distilled water, and non-pure water (ultrafiltration water, mineral water, tap water). Summary of the Invention
[0006] This invention provides a method, apparatus, sensor, and electrical appliance for detecting the level of non-conductive or conductive liquids, which can effectively and accurately detect the level of liquids of different conductivity, such as water, and can even detect the level of liquid oils.
[0007] In a first aspect, the present invention provides a method for detecting the level of non-conductive or conductive liquids, comprising the steps of: firstly fabricating a DC power-driven multivibrator, setting an oscillation / stop oscillation control terminal and an oscillator signal output terminal on the multivibrator, and connecting a metal liquid level sensing probe to the oscillation / stop oscillation control terminal;
[0008] When the measured liquid level reaches or exceeds the height of the metal liquid level sensor, the multivibrator stops oscillating, and the oscillator signal output terminal outputs a high or low level; when the measured liquid level is lower than the height of the metal liquid level sensor, the multivibrator self-excites and oscillates, and the oscillator signal output terminal outputs an unsteady pulse oscillation signal, thereby identifying the height position of the liquid level.
[0009] Furthermore, the non-conductive liquid includes non-conductive pure water, reverse osmosis filtered pure water with poor conductivity, and distilled water; the conductive liquid includes water found in nature, mineral water, tap water, and its ultrafiltered water.
[0010] Preferably, the liquid is water or an aqueous liquid.
[0011] Furthermore, at least one trigger capacitor is connected in series between the oscillation / stop oscillation control terminal and the metal liquid level sensing probe.
[0012] Furthermore, the trigger capacitor is a strong / weak current isolation capacitor C2, C3.
[0013] Furthermore, the oscillator signal output terminal directly outputs a digital voltage signal output terminal Vod; or, if an RC filter circuit is connected to the oscillator signal output terminal, it forms an analog voltage signal output terminal Voa that outputs an analog voltage signal.
[0014] Preferably, the metal liquid level sensing probe is a contact sensing probe.
[0015] Furthermore, a computer detection and control device MCU corresponding to the specific application is connected to the digital voltage signal output terminal Vod or the analog voltage signal output terminal Voa, and the DC power supply is grounded systematically.
[0016] Furthermore, the multivibrator is composed of a 555 / 556 timer circuit, with its high threshold trigger terminal THR and low threshold trigger terminal TR connected in parallel as the signal input terminal to form the oscillation / stop oscillation control terminal, and the signal output terminal is the out pin to form the oscillator signal output terminal.
[0017] Furthermore, the pulse oscillation signal is a square wave.
[0018] Furthermore, the multivibrator is a typical astable multivibrator composed of two transistors and resistor and capacitor circuits, wherein the output terminal of one transistor is selected as the oscillator signal output terminal, and the metal liquid level sensing probe is connected to its self-excitation control terminal.
[0019] Furthermore, the pulse oscillation signal is a triangular wave or a sine wave. Furthermore, the computer detection and control device MCUC includes an embedded or single-chip computer, and one of the computer's digital signal input interfaces In1 or an analog-to-digital converter (A / D) is connected to the digital voltage signal output terminal Vod or the analog voltage signal output terminal Voa.
[0020] Further, the computer identifies the liquid level sensed by the metal liquid level sensor probe using one of the following two methods: (1) When the corresponding digital signal input interface In1 of the computer detects that the received signal is a stable high or low level, it determines that the liquid level has reached or exceeded the position of the metal liquid level sensor probe; when the corresponding digital signal input interface In1 of the computer detects that the received signal is a pulse oscillation signal, it determines that the liquid level is lower than the position of the metal liquid level sensor probe; (2) When the corresponding analog / digital conversion interface A / D of the computer detects that the received signal is a high voltage close to the power supply voltage or a low voltage close to zero voltage, it determines that the liquid level has reached or exceeded the position of the metal liquid level sensor probe; when the corresponding analog / digital conversion interface A / D of the computer detects that the received signal is an intermediate value between the high voltage and the low voltage, it determines that the liquid level is lower than the position of the metal liquid level sensor probe.
[0021] Secondly, the present invention provides a liquid level detection device made by a method for detecting the liquid level of a non-conductive or conductive liquid, wherein the device for detecting the liquid level of a non-conductive or conductive liquid is made by the method described.
[0022] Thirdly, the present invention provides a sensor for detecting the level of non-conductive or conductive liquids, wherein the device for detecting the level of non-conductive or conductive liquids is packaged as a sensor.
[0023] Fourthly, the present invention provides an electrical appliance having the aforementioned device or sensor, wherein the electrical appliance includes an electric kettle, an electric tea stove, a water dispenser, a water purifier, and a boiler.
[0024] Fifthly, the present invention provides a liquid level sensor, comprising a liquid level detection device manufactured by the method for detecting the liquid level of non-conductive or conductive liquids, wherein multiple metal liquid level sensing probes are arranged longitudinally and sequentially in the liquid to be measured; each metal liquid level sensing probe is connected to the corresponding input terminal of a multi-channel electronic switch, and the output terminal of the multi-channel electronic switch is connected to the input terminal of the liquid level detection device for detecting non-conductive or conductive liquids. A computer detection and control device MCU scans the address of the multi-channel switch to select the corresponding switch, determines whether the metal liquid level sensing probe has detected the liquid level signal, and determines the liquid level of the liquid to be measured.
[0025] Furthermore, the liquid being tested includes liquid grease.
[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: The suspended metal induction probe forms a detection circuit with the ground through the medium with different dielectric constants contained in the container. The medium that can be detected is conductive or non-conductive liquid containing water with low conductivity, or air. Depending on the mode of the circuit output signal, the waveform is different, thereby distinguishing whether the water exceeds or submerges the water level probe to determine the water level height. This effectively solves the problem that traditional electrode-type liquid level detection sensors cannot detect due to the lack of conductivity of pure water, etc., and the accuracy is prone to errors or even failure to detect. At the same time, the stainless steel material will not or is not easily electrolyzed and rusted, nor will it be covered by scale and cause failure. Moreover, installation is convenient and quick, only requiring the opening of a mounting hole in the container, and the cost is low. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the implementation environment of a method for detecting the level of non-conductive or conductive liquids according to an embodiment of the present invention;
[0028] Figure 2 This is a schematic diagram of the structure of a liquid level detection device for detecting the level of non-conductive or conductive liquids provided in an embodiment of the present invention;
[0029] Figure 3 This is a schematic diagram of the internal structure of the NE555 chip;
[0030] Figure 4 It is a triangular waveform signal generated at points C and D at the common terminal of the parallel connection of the high threshold trigger terminal THR and the low threshold trigger terminal TR of the NE555DR chip when the water level probe is not in contact with the water.
[0031] Figure 5 It is a square waveform signal generated at points A and B of the output terminal of the NE555DR chip when the water level probe is not in contact with the water.
[0032] Figure 6It is the filtered signal generated at points C and D at the common terminal of the parallel connection of the high threshold trigger terminal THR and the low threshold trigger terminal TR of the NE555DR chip when the water level probe comes into contact with water.
[0033] Figure 7 It is the low-level signal output from pin 3 of the NE555 after filtering when the water level probe comes into contact with the water;
[0034] Figure 8 It is the high-level signal output from pin 3 of the NE555 after filtering when the water level probe comes into contact with the water;
[0035] Figure 9 This is a flowchart illustrating the process of a liquid level detection device detecting whether there is water on the high and low water level probes; the judgment thresholds for V1 and V2 can be preset.
[0036] Figure 10 This is a schematic diagram of the circuit structure of a liquid level sensor provided in an embodiment of the present invention;
[0037] Figure 11 This is a schematic diagram of a process for a liquid level sensor to detect whether there is water at multiple water level detection points, according to an embodiment of the present invention. Detailed Implementation
[0038] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, solution, and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.
[0039] See Figure 1 This is a schematic diagram of the implementation environment of a method for detecting the level of non-conductive or conductive liquids according to an embodiment of the present invention. The method includes the following steps:
[0040] Step 1: First, make a DC power supply driven multivibrator. Set an oscillation / stop oscillation control terminal and an oscillator signal output terminal on the multivibrator. Connect a metal liquid level sensing probe to the oscillation / stop oscillation control terminal.
[0041] In this step, the multivibrator is the time base circuit of NE555DR. Its high threshold trigger terminal THR and low threshold trigger terminal TR are connected in parallel as the signal input terminal to form the oscillation / stop oscillation control terminal. The signal output terminal is the out pin, which forms the oscillator signal output terminal.
[0042] The metal liquid level sensor is a contact-type sensor, specifically a water level (metal) probe, which is actually a tiny metal rod. The signal output terminal of the water level probe is connected to the input terminal of the oscillation / stop oscillation control terminal.
[0043] The water level probe is insulated from the container wall, which is entirely metal and connected to ground. Alternatively, the container wall may be partially metal, such as in a kettle with glass circumferential walls, and the bottom wall may be made of metal that contacts the heating plate and is grounded. The water level probe and the inner metal wall of the container form a capacitor structure.
[0044] Optionally, the container wall is made of a non-conductive material, such as a container with an inner wall entirely made of ceramic. A perforation is drilled in the bottom wall of the container to create a water seal, and a metal ring extends into the container. A grounding wire is led out from the metal ring to the outside of the container. The water level probe extends from holes in the four sides of the container wall and is water-sealed. The water level probe and the metal ring together form a capacitor structure.
[0045] Grounding is used to prevent water leakage from the container wall and to form a circuit for the capacitor structure.
[0046] Step 2: When the measured liquid level reaches or exceeds the height of the metal liquid level sensor probe, the multivibrator stops oscillating, and the oscillator signal output terminal outputs a high level or a low level; when the measured liquid level is lower than the height of the metal liquid level sensor probe, the multivibrator self-excites and oscillates, and the oscillator signal output terminal outputs an unsteady pulse oscillation signal, thereby identifying the height position of the liquid level.
[0047] In this step, when the water level probe is not in contact with water, it forms a capacitor with the container wall using air as the medium. This can be understood as air being a non-conductive medium, generally lacking the ability to form a capacitor. Therefore, there is no charge between the water level probe and the container wall; the probe is suspended and there is no input signal. The oscillation circuit inside the NE555DR chip generates an oscillation signal, which is output at pin 3 (OUT) of the NE555DR chip, i.e., the signal at point A. The output waveform of this signal is an astable (approximate) square wave pulse signal. See [link to relevant documentation]. Figure 5 .
[0048] When the water level probe contacts water, it forms a capacitance with the water as the dielectric between the probe and the metal part of the container wall. Its output signal is input to the common terminal of the parallel connection between the high threshold trigger terminal (THR) and the low threshold trigger terminal (TR) of the NE555DR chip. The internal oscillation circuit of the NE555DR chip stops generating the oscillation signal, and the signal is output at pin OUT3 of the NE555DR chip. Figure 1 The signal at point A, after filtering, outputs either a high-level or low-level signal. (See [reference needed]). Figure 7 , Figure 8 .
[0049] Based on the difference in dielectric constant of the capacitor between the water level probe and the container's metal wall (or metal ring), and by comparing the changes in the dielectric material of the capacitor—for example, the output signal obtained by the dielectric material of air differs from the output signal of the dielectric material of pure water with low conductivity—the two signals and waveforms are different, allowing the determination of whether the liquid level has reached the water level probe. By placing several water level probes at different heights within the container, the liquid level position can be determined. Therefore, the liquid level height of various conductive and non-conductive liquids can be measured.
[0050] Based on the above embodiment, two high-voltage ceramic capacitors C2 and C3 are connected in series between the oscillation / stop oscillation control terminal and the metal liquid level sensing probe. In this solution, these high-voltage ceramic capacitors C2 and C3 are used to isolate the 220V high-voltage current when the water level probe contacts water and there is leakage, thus protecting the host computer circuitry. If the host computer circuit board leaks current, the two capacitors can ensure that the water in the isolation container is not energized, preventing people from coming into contact with the leaking water, thereby achieving bidirectional protection.
[0051] Trigger capacitors C2 and C3 can be either high-voltage or low-voltage, and their voltage ratings can be greater than 220V, 400V, 800V, or 1000V. As the rated voltage increases, the capacitor size also increases. In applications with limited installation space, such as electric kettles, two small capacitors C2 and C3 can be connected in series to reduce size, thus solving the installation space problem of high / low voltage safety isolation circuits with minimal space.
[0052] Based on the above embodiment, a resistor-capacitor filter circuit R1 and C1 are connected to the oscillator signal output terminal to form the output analog voltage signal. This solution can filter out noise from the output signal and stabilize the voltage. See also Figure 1 When the water level probe touches or exceeds the water level, the output signal at pin 3 (point A) of the NE555DR chip is filtered by the RC filter to obtain a stable signal at MCU-IO1. Based on the parameters of the RC filter components R1, C1, and R3, the signal at point A can be filtered and stabilized into a high-level signal at MCU-IO1. (See [link to relevant documentation]). Figure 8 Alternatively, the signal at point A can be filtered and stabilized into a low-level signal at MCU-IO1. See [link / reference]. Figure 7 .
[0053] Based on the above embodiments, a computer detection and control device (MCU) corresponding to a specific application can be connected to the digital voltage signal output terminal. In this solution, the computer detection and control device (MCU) can record the initial state and current state of the water level probe, as well as compare and calculate the current signals of multiple water level probes to determine the water level position inside the container. The computer detection and control device (MCU) includes an embedded or single-chip computer, and the computer's designated digital signal input interface or designated analog-to-digital conversion interface (A / D) is connected to the digital voltage signal output terminal or analog voltage signal output terminal respectively.
[0054] Based on the above embodiments, the non-conductive liquid includes pure water (with poor conductivity), such as purified water or distilled water, as well as spring water, tap water, and ultrafiltered water containing conductive substances. In this solution, compared to ordinary tap water, mineral water and other mineral-rich water can act as a conductive medium, allowing the water level probe to detect electrical signals. However, purified water or distilled water does not have a conductive medium. A contact-type induction probe is used as a metal liquid level sensing probe. Utilizing the difference in dielectric constant between the water level probe and the container wall (e.g., the dielectric constant of air differs from that of purified water or distilled water), different output signals and waveforms are measured to distinguish whether the liquid level has reached the probe. By using several water level probes placed at different heights within the container, the liquid level position is determined.
[0055] Based on the above embodiments, optionally, the multivibrator is a typical astable multivibrator composed of two transistors and resistor and capacitor circuits, wherein the output terminal of one transistor is selected as the oscillator signal output terminal, and the metal liquid level sensing probe is connected to its self-excitation control terminal.
[0056] Based on the above embodiments, the computer identifies the liquid level sensed by the metal liquid level sensor probe in either of the following two methods: (1) When the corresponding digital signal input interface (In1) of the computer detects that the received signal is a stable high or low level, it determines that the liquid level has reached or exceeded the position of the metal liquid level sensor probe; when the corresponding digital signal input interface of the computer detects that the received signal is a pulse oscillation signal, it determines that the liquid level is lower than the position of the metal liquid level sensor probe.
[0057] (2) When the corresponding analog-to-digital converter (A / D) of the computer detects that the received signal is a high voltage that is close to the power supply voltage or a low voltage that is close to zero voltage, it determines that the liquid level has reached or exceeded the position of the metal liquid level sensor probe; when the corresponding analog-to-digital converter (A / D) of the computer detects that the received signal is an intermediate value between the high voltage and the low voltage, it determines that the liquid level is lower than the position of the metal liquid level sensor probe.
[0058] See Figure 2 This is a schematic diagram of a liquid level detection device for detecting the level of non-conductive or conductive liquids according to an embodiment of the present invention. The device includes a high-level probe and a low-level probe, the outputs of which are respectively connected to the inputs of a set of water level detection circuits. The outputs of the two sets of water level detection circuits are respectively connected to the inputs of the MCU chip in the computer detection and control device, MCU-IO1 and MCU-IO2. The high-level probe and low-level probe are disposed inside a container; in this embodiment, a kettle is used as an example. Due to the limited space of the kettle, the inner wall of the kettle is made of metal and is grounded. Holes are provided on the inner wall, through which the silicone-coated water level probe passes, allowing the probe to contact the water inside the kettle. Optionally, the water level probe is insulated from the kettle; the circumferential wall of the kettle is glass, and the bottom wall is a metal material that contacts the heating plate and is grounded. The water level probe and the metal inner wall of the container form a capacitor structure.
[0059] Optionally, the kettle wall is made of a non-conductive material, such as a container with an entirely ceramic inner wall. A perforation is made in the bottom wall of the container, and a water seal is established to extend a metal ring into the kettle. A grounding wire is led out from the metal ring to the outside of the kettle. A water level probe extends from holes in the surrounding walls of the kettle and is water-sealed. The water level probe and the metal ring together form a capacitor structure.
[0060] Grounding is used to prevent water leakage from the container wall and to form a circuit for the capacitor structure.
[0061] See Figure 2 The water level detection circuit includes NE555 multivibrator chips U1 and U2. The output of the high water level probe is connected to two high-voltage ceramic capacitors C3 and C4 in series, and a pull-down resistor R3 branch. The output of this branch is connected to the common terminal of the parallel connection of the high threshold trigger THR and low threshold trigger TR of the NE555DR chip U1. The output pin OUT of the NE555DR chip is connected to the filter circuit of R2 and C2. The common terminal of resistor R2 and capacitor C2 is connected to the current-limiting resistor R4, and the second input terminal MCU-IO2 of the MCU chip U3. The output of the low water level probe is connected to two high-voltage ceramic capacitors C5 and C6 in series, and a pull-down resistor R5 branch. The output of this branch is connected to the common terminal of the parallel connection of the high threshold trigger THR and low threshold trigger TR of the NE555 chip U2. The output pin OUT of the NE555 chip is connected to the filter circuit of R1 and C1. The common terminal of resistor R1 and capacitor C2 is connected to the current-limiting resistor R6, and the first input terminal MCU-IO1 of the MCU chip U3.
[0062] C3, C4, C5, C6: 10pF~100nF
[0063] C1, C2:nF~1Uf
[0064] R1, R2, R3, R4, R5, R6: 1kΩ~100MΩ
[0065] C3, C4, C5, and C6 are high-voltage ceramic capacitors used for filtering and high-voltage isolation.
[0066] R3 and R5 are pull-down resistors.
[0067] R4 and R6 are current-limiting resistors. R1 and C1, R2 and C2 form an RC filter circuit, which makes the square wave signal output at points A and B have an effective average voltage value. The larger R is, the more stable the voltage.
[0068] MCU-IO1 and MCU-IO2 are set to analog input mode to detect voltage values, and the kettle body is connected to GND.
[0069] The NE555 multivibrator chip in this embodiment can be replaced with an NE556 chip.
[0070] See Figure 3 This is a schematic diagram of the internal structure of the NE555 chip. The input voltage Va is at the high threshold trigger terminal THR, and the input voltage Vb is at the low threshold trigger terminal TR. The NE555 chip mainly consists of three parts: a voltage divider circuit, a voltage comparator, and an RS flip-flop. The voltage divider circuit provides the comparison voltage for the voltage comparator; the voltage comparator outputs high and low levels based on the trigger signal; and the RS flip-flop outputs a rectangular wave.
[0071] Combination Figure 2 and Figure 3 The input voltage and input / output logic of the NE555 chip are shown in Table 1 and Table 2 below:
[0072] Table 1
[0073] Va Vb R S Q >2 / 3Vcc >1 / 3Vcc 0 1 0 <2 / 3Vcc >1 / 3Vcc 1 1 Maintain the original state <2 / 3Vcc <1 / 3Vcc 1 0 1
[0074] Table 2
[0075] Va = Vb R S Q 0V 1 0 1 >1 / 3Vcc 1 1 Maintain the original state >2 / 3Vcc 0 1 0 <2 / 3Vcc 1 1 Maintain the original state <1 / 3Vcc 1 0 1
[0076] When the kettle is empty, C3, C4, R3 and C5, C6, R5 are in a floating state. When the NE555 timer is working, points C and D will generate an approximately triangular waveform signal, as shown below. Figure 4When C=0 and D=0, points A and B output 1; when C>1 / 3Vcc and D>1 / 3Vcc, points A and B maintain their original state and still output 1; when C>2 / 3Vcc and D>2 / 3Vcc, points A and B output 0, and the level flips; when C<2 / 3Vcc and D<2 / 3Vcc, points A and B maintain their original state and still output 0; when C<1 / 3Vcc and D<1 / 3Vcc, points A and B output 1, and the level flips. Thus, points A and B will output a square wave signal as follows: Figure 5 The square wave signal has a frequency of approximately 50Hz and a duty cycle of approximately 1 / 2. The voltage values measured at the MCU-IO1 and MCU-IO2 pins are approximately 1 / 2VCC.
[0077] When the kettle contains water and the water level is above the probe, the probe and the metal wall of the kettle are essentially connected to a capacitor connected to GND, forming a circuit. Connecting C3, C4, R3 and C5, C6, R5 can filter the signal. Figure 2 This causes the voltage values at points C and D to decrease. When C < 1 / 3Vcc and D < 1 / 3Vcc, points A and B output 1; when C > 2 / 3Vcc and D > 2 / 3Vcc, points A and B output 0; when 1 / 3Vcc < C < 2 / 3Vcc and 1 / 3Vcc < D < 2 / 3Vcc, points A and B remain in their original state, while the voltage at point C or D increases from less than 1 / 3Vcc to greater than 1 / 3Vcc but less than 2 / 3Vcc, causing points A and B to output 1; conversely, when the voltage at point C or D decreases from greater than 2 / 3Vcc to less than 2 / 3Vcc but greater than 1 / 3Vcc, points A and B output 0. Therefore, the output signal of pin 3 of the NE555 is as follows: Figure 7 Or such as Figure 8 The voltage values measured on the MCU-IO1 and MCU-IO2 pins are approximately 0 or VCC. This allows us to determine the high and low states of the kettle.
[0078] See Figure 2 When the water level probe touches or exceeds the water level, the output signal at pin 3 (point A) of the NE555DR chip U2 is filtered by the RC filter to obtain a stable signal at MCU-IO1. Based on the parameters of the RC filter components R1, C1, and R6, the signal at point A can be filtered and stabilized into a high-level signal at MCU-IO1. (See [link to relevant documentation]). Figure 8 Alternatively, the signal at point A can be filtered and stabilized into a low-level signal at MCU-IO1. See [link / reference]. Figure 7 Similarly, based on the parameters of the RC filter components R2, C2, and R4, the signal at point B can be filtered and stabilized into a high-level signal at MCU-IO2. (See [link to relevant documentation]). Figure 8 Alternatively, the signal at point B can be filtered and stabilized into a low-level signal at MCU-IO2. See [link / reference]. Figure 7。
[0079] See Figure 9 , set the voltage of VCC to 5V, and the threshold for judging whether there is water or not is The threshold is 1.5V; the threshold for judging whether there is water or not is The threshold is 3.5V; the actual voltage V1 measured at the MCU-IO2 pin (high water level). If V1 < 1.5V, there is water at the high water level, and the output signal diagram is shown in Figure 7 , if V1 > 3.5V, there is water at the high water level, and the output signal diagram is shown in Figure 8 ; when 1.5 < V1 < 3.5V, there is no water at the high water level. The method for judging the low water level is the same.
[0080] Among them, the threshold is is the low voltage threshold of the signal at MCU-IO1 after RC filtering, and the threshold is is the high voltage threshold of the signal at MCU-IO1 after RC filtering.
[0081] In this embodiment, a capacitor structure is formed by the water level probe and the inner wall of the kettle. By comparing the changes in the dielectric materials of the capacitor, such as the output signals obtained from the air dielectric material being different from those of the pure water dielectric material, it is thus possible to judge whether the water level probe is submerged or contacted by the water in the kettle based on different signals. Combining the output signals of the high and low water level probes, the position of the liquid in the kettle is determined.
[0082] A sensor for detecting the liquid level of non-conductive or conductive liquids provided by an embodiment of the present invention encapsulates the liquid level detection device for detecting the liquid level of non-conductive or conductive liquids in the embodiment as a sensor.
[0083] An electrical appliance provided by an embodiment of the present invention internally incorporates the liquid level detection device for detecting the liquid level of non-conductive or conductive liquids in the embodiment. The electrical appliance can be an electric kettle, an electric tea stove, a water dispenser, or a water purifier. The method for the electrical appliance to detect the liquid level of non-conductive or conductive liquids is as described in the method embodiment; the high and low water level probes of the liquid level detection device for detecting the liquid level of non-conductive or conductive liquids are arranged on the inner wall of the kettle of the electrical appliance, the metal bottom wall of the water container of the electrical appliance or the metal ring extending from the insulating bottom wall is grounded, and the water level detection circuit and the computer detection and control device Mcu chip are arranged in the main body part of the electrical appliance. The specific implementation manner is as described in the device embodiment and will not be elaborated here.
[0084] See Figure 10This is a circuit diagram of a liquid level sensor provided in an embodiment of the present invention. The sensor includes a liquid level detection device manufactured by the method for detecting the level of non-conductive or conductive liquids. The metal liquid level sensing probe consists of five water level probes arranged vertically in a water tank. One water level probe is grounded, and the other four water level probes are respectively connected to the input terminals of a single-ended 8-channel multiplexer CD4051 chip. One output pin 3 of the CD4051 chip is connected to the water level detection circuit, which is described in [reference needed]. Figure 1 The circuit structure within the dashed box. The output terminal MCU-IO1 of this water level detection circuit is connected to pin 5 of the input terminal of the computer detection and control device U3-NY8B062FS8.
[0085] The water bucket is made of non-conductive material, and the inner wall of the bucket is usually made entirely of polycarbonate. Several vertical holes are drilled in the circumferential wall of the bucket. Water level probes are water-sealed through the holes and can contact the water inside the bucket. One of the water level probes is led out to the outside of the bucket with a grounding wire. Grounding is to prevent the water inside the bucket from becoming electrified due to leakage from the host computer, which can play a role in electrical safety. The grounded water level probe and the other four water level probes form a capacitor structure to form a circuit.
[0086] See Figure 11 This is a schematic diagram illustrating the process of the sensor detecting the presence of water at multiple water level detection points in this embodiment. The computer detection and control device U3-NY8B062FS8 continuously scans the A, B, and C pins of the CD4051 chip, inputting binary address signals from channels 0-7 to determine the selection of the corresponding switch, acquiring the signals of the water level probes connected to the corresponding switches, and detecting whether the water level has reached or exceeded the water level probes. By analyzing the four water level probes to determine whether the water level in the bucket has been reached or exceeded, the computer detection and control device U3-NY8B062FS8 determines whether the water in the bucket needs to be replenished in time, and whether to send a signal to the host computer of the water appliance to stop pumping water, preventing water from being pumped even when the bucket is empty.
[0087] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this disclosure, as long as they achieve the same technical effects, should be included within the scope of protection of this disclosure and fall under the protection scope of the present invention. Within the protection scope of the present invention, the technical solutions and / or implementation methods can have various modifications and variations.
Claims
1. A method for detecting the level of a non-conductive or conductive liquid, characterized in that, First, a DC power supply driven multivibrator is made. An oscillation / stop oscillation control terminal and an oscillator signal output terminal are set on the multivibrator. A metal liquid level sensing probe is connected to the oscillation / stop oscillation control terminal. When the measured liquid level reaches or exceeds the height of the metal liquid level sensor, the multivibrator stops oscillating, and the oscillator signal output terminal outputs a high or low level; when the measured liquid level is lower than the height of the metal liquid level sensor, the multivibrator self-excites and oscillates, and the oscillator signal output terminal outputs an unsteady pulse oscillation signal, thereby identifying the height position of the liquid level.
2. The method for detecting the level of non-conductive or conductive liquids according to claim 1, characterized in that, The non-conductive liquids include non-conductive pure water, purified water filtered through reverse osmosis with poor conductivity, and distilled water; the conductive liquids include water found in nature, mineral water, tap water, and their ultrafiltered water.
3. The method for detecting the level of non-conductive or conductive liquids according to claim 1, characterized in that, The liquid is water or an aqueous liquid.
4. The method for detecting the level of non-conductive or conductive liquids according to claim 1, characterized in that, At least one trigger capacitor is connected in series between the oscillation / stop oscillation control terminal and the metal liquid level sensing probe.
5. The method for detecting the level of non-conductive or conductive liquids according to claim 4, characterized in that, The trigger capacitor is a strong / weak current isolation capacitor (C2, C3).
6. The method for detecting the level of non-conductive or conductive liquids according to claim 1, characterized in that, The oscillator signal output terminal directly outputs a digital voltage signal output terminal (Vod); or, if an RC filter circuit is connected to the oscillator signal output terminal, it forms an analog voltage signal output terminal (Voa) that outputs an analog voltage signal.
7. The method for detecting the level of non-conductive or conductive liquids according to claim 1, characterized in that, The metal liquid level sensing probe is a contact-type sensing probe.
8. The method for detecting the level of a non-conductive or conductive liquid according to any one of claims 1-7, characterized in that, A computer detection and control device (MCU) for a specific application is connected to the digital voltage signal output terminal (Vod) or the analog voltage signal output terminal (Voa), and the DC power supply is grounded systematically.
9. The method for detecting the level of a non-conductive or conductive liquid according to claim 8, characterized in that, The multivibrator is composed of a 555 / 556 timer circuit. Its high threshold trigger (THR) and low threshold trigger (TR) terminals are connected in parallel as signal input terminals to form the oscillation / stop oscillation control terminal. The signal output terminal is the out pin, which forms the oscillator signal output terminal.
10. The method for detecting the level of a non-conductive or conductive liquid according to claim 9, characterized in that, The pulse oscillation signal is a square wave.
11. The method for detecting the level of a non-conductive or conductive liquid according to claim 8, characterized in that, The multivibrator is a typical astable multivibrator composed of two transistors and resistor and capacitor circuits. The output terminal of one of the transistors is selected as the oscillator signal output terminal, and the metal liquid level sensing probe is connected to its self-excitation control terminal.
12. The method for detecting the level of a non-conductive or conductive liquid according to claim 11, characterized in that, The pulse oscillation signal is a triangular wave or a sine wave.
13. The method for detecting the level of a non-conductive or conductive liquid according to claim 8, characterized in that, The computer detection and control device (MCU) includes an embedded or single-chip computer, and the corresponding digital signal input interface (In1) or analog / digital conversion interface (A / D) of the computer is connected to the corresponding digital voltage signal output terminal (Vod) or analog voltage signal output terminal (Voa).
14. The method for detecting the level of a non-conductive or conductive liquid according to claim 13, characterized in that, The computer identifies the liquid level sensed by the metal liquid level sensor probe using one of the following two methods: (1) When the corresponding digital signal input interface (In1) of the computer detects that the received signal is a stable high or low level, it determines that the liquid level has reached or exceeded the position of the metal liquid level sensor probe; when the corresponding digital signal input interface (In1) of the computer detects that the received signal is a pulse oscillation signal, it determines that the liquid level is lower than the position of the metal liquid level sensor probe; (2) When the corresponding analog / digital converter interface (A / D) of the computer detects that the received signal is a high voltage close to the power supply voltage or a low voltage close to zero voltage, it determines that the liquid level has reached or exceeded the position of the metal liquid level sensor probe; when the corresponding analog / digital converter interface (A / D) of the computer detects that the received signal is an intermediate value between the high voltage and the low voltage, it determines that the liquid level is lower than the position of the metal liquid level sensor probe.
15. A device for detecting the level of non-conductive or conductive liquids, characterized in that, A device for detecting the level of non-conductive or conductive liquids, made using the method described in claims 1-14.
16. A sensor for detecting the level of non-conductive or conductive liquids, characterized in that, The device as described in claim 15 is packaged as a sensor.
17. An electrical appliance, characterized in that, The electrical appliance is equipped with the device as described in claim 15 or the sensor as described in claim 16, wherein the electrical appliance includes an electric kettle, an electric tea stove, a water dispenser, a water purifier, and a boiler.
18. A liquid level sensor, characterized in that, The liquid level detection device includes a method for detecting the level of non-conductive or conductive liquids as described in any of claims 8-14, wherein multiple metal liquid level sensing probes are arranged longitudinally and sequentially in the liquid to be measured; each metal liquid level sensing probe is connected to the corresponding input terminal of a multi-channel electronic switch, the output terminal of the multi-channel electronic switch is connected to the input terminal of the detection device for detecting the level of non-conductive or conductive liquids, and the corresponding switch is selected by scanning the address of the multi-channel switch through a computer detection and control device (MCU) to determine whether the metal liquid level sensing probe has detected the liquid signal to be measured, thereby determining the liquid level of the liquid to be measured.
19. The liquid level sensor according to claim 18, characterized in that, The liquid being tested includes liquid grease.