Device for detecting liquid level of non-conductive or conductive liquid, sensor and electric appliance

Abstract

The utility model relates to a non-conductive or conductive liquid level detection device, a sensor and an electric appliance, and the device comprises a multivibrator driven by a direct-current power supply, and the multivibrator is provided with an oscillation / oscillation stopping control end and an oscillator signal output end. A metal liquid level sensing probe is connected to the oscillation / oscillation stopping control end; when the measured liquid level reaches or exceeds the height of the metal liquid level sensing probe, the multivibrator stops oscillating, and the signal output end of the oscillator outputs a high level or a low level; when the measured liquid level is lower than the height of the metal liquid level sensing probe, the multivibrator performs self-oscillation, the signal output end of the oscillator outputs an astable pulse oscillation signal, and the height position of the liquid level is recognized according to the output state. The liquid level detection device can effectively and accurately detect the liquid levels of liquids with different electrical conductivity water qualities, even can detect the liquid level of liquid grease, and particularly can detect non-conductive pure water and distilled water.

Description

TECHNICAL FIELD

[0001] The utility model relates to sensor technical field, concretely relates to a device for detecting non-conductive or conductive liquid level, sensor and electric appliance. BACKGROUND

[0002] At present, the mainstream method for detecting the liquid level of conductive liquid (usually refers to water-containing liquid) in a container is the traditional ordinary electrode type and capacitance type. For example, the water level detection of a kettle is achieved by installing an electrode needle in direct contact with water in the kettle, using the conductivity of water to detect the water level, applying a certain low voltage to the electrode probe, passing through the water equivalent to a certain resistance, passing through a voltage dividing circuit to detect the change of voltage, and thus determining whether there is water at a certain liquid level in the kettle.

[0003] However, the electrode type detection has the following problems: 1. This method may cause different detection voltages due to different water qualities, different conductivities, and other factors equivalent to different resistance values. For example, the resistance of reverse osmosis pure water is high, up to 10-15 megaohm centimeters or more. Because pure water or ultrapure water contains no or very few minerals, impurities or other electrolytes, its conductivity is very low or even theoretically non-conductive, so the current through the electrode is very small; while tap water containing many minerals has a low resistivity, so the current through the electrode is relatively large. Therefore, the same amount of water will produce different currents due to different water qualities, and the voltage detected by the voltage dividing circuit will be greatly different, thus often causing misjudgment and failure to detect normally. 2. Because the electrode probe is installed in direct contact with water in the kettle, after a long period of use, the electrode probe will be corroded due to electrolysis when measuring the current, even if it is made of stainless steel. The electrode probe will be rusted and wrapped by scale, resulting in failure to detect, so the electrode probe cannot conduct electricity or its conductivity decreases, thus easily causing misjudgment and failure to detect normally. For insulating liquid oil (such as edible oil), there is no probe contact method for detecting water.

[0004] The capacitance type detection method is generally non-contact and closely attached to the outside of the container, which is easily affected by temperature. For example, the liquid in the kettle may be heated to a very hot state, which may cause inaccurate detection. In addition, the continuously boiling and turbulent liquid in the kettle and the water vapor evaporated by heating may also cause misjudgment and failure to detect normally.

[0005] Therefore, there is an urgent need for a liquid level detection device that can effectively and accurately detect different water qualities, such as pure water, pure water, distilled water and non-pure water (ultrafiltration water, mineral water, tap water). SUMMARY

[0006] The utility model provides a non -conducting or conductive liquid level detection device, sensor and electrical equipment, can effectively accurate detection different conductivity water quality's liquid level, even can detect liquid oil's liquid level.

[0007] First, the utility model provides a non -conducting or conductive liquid level detection device, including the multivibrator of direct current power drive, set up an oscillation / stop oscillation control end and an oscillator signal output end on this multivibrator, have a metal liquid level inductive probe on oscillation / stop oscillation control end connection;

[0008] When the measured liquid level reaches or exceeds the height of metal liquid level inductive probe, the multivibrator stops oscillation, and the oscillator signal output end outputs high level or low level;When the measured liquid level is lower than the height of metal liquid level inductive probe, the multivibrator self -excitation oscillation, and the oscillator signal output end outputs no steady state pulse oscillation signal, and thus the output state identifies the height position of liquid level.

[0009] Further, the non -conducting liquid includes non -conducting pure water, poor conductivity reverse osmosis filtered pure water, distilled water;The conductive liquid includes water in nature, mineral water, tap water and its ultrafiltration water.

[0010] Preferably, the liquid is water or aqueous liquid.

[0011] Further, at least one trigger capacitor is connected in series between the oscillation / stop oscillation control end and the metal liquid level inductive probe.

[0012] Further, the trigger capacitor is a strong / weak electric isolation capacitor C2, C3.

[0013] Further, the oscillator signal output end directly outputs a digital voltage signal output end Vod;Or, the analog voltage signal output end Voa outputting analog voltage signal is formed by connecting a resistance-capacitance filter circuit on the oscillator signal output end.

[0014] Preferably, the metal liquid level inductive probe is a contact inductive probe.

[0015] Preferably, the digital voltage signal output end Vod or the analog voltage signal output end Voa is connected with the computer detection control device Mcu corresponding to the specific application occasion, and the system ground of the direct current power supply is grounded.

[0016] Further, the multivibrator is composed of 555 / 556 time base circuit, and the high threshold trigger end THR and the low threshold trigger end TR are connected in parallel as the signal input end to form the oscillation / stop oscillation control end, and the signal output end is the out pin to form the oscillator signal output end.

[0017] Further, the pulse oscillation signal is a square wave.

[0018] Further, the multivibrator is a typical astable multivibrator composed of two triodes and resistance-capacitance circuit, wherein the output end of an optional triode is connected with the metal liquid level sensing probe at the self-oscillation control end as the oscillator signal output end.

[0019] Further, the pulse oscillation signal is a triangular wave or a sine wave.

[0020] Further, the computer detection control device Mcu contains 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 with the corresponding digital voltage signal output end Vod or analog voltage signal output end Voa.

[0021] Further, the non-conductive or conductive liquid level detection device judges that the liquid level reaches or exceeds the position of the metal liquid level sensing probe when the corresponding digital signal input interface In1 of the computer detects that the received signal is a stable high or low level; judges that the liquid level is lower than the position of the metal liquid level sensing probe when the corresponding digital signal input interface In1 of the computer detects that the received signal is a pulse oscillation signal; or judges that the liquid level reaches or exceeds the position of the metal liquid level sensing probe 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; judges that the liquid level is lower than the position of the metal liquid level sensing 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.

[0022] In the second aspect, the utility model provides a kind of sensor for detecting the liquid level of non-conductive or conductive liquid, and the device for detecting the liquid level of non-conductive or conductive liquid is packaged as liquid level sensor.

[0023] In the third aspect, the utility model provides a kind of electric appliance made of method for detecting the liquid level of non-conductive or conductive liquid, and the electric appliance is provided with the device for detecting the liquid level of non-conductive or conductive liquid or the liquid level sensor, wherein, electric appliance includes electric kettle, electric tea stove, water dispenser, water purifier and boiler.

[0024] In a fourth aspect, the utility model provides a kind of sensor, including the liquid level detection device made of the method of the detection non-conductive or conductive liquid level, wherein metal liquid level sensing probe is arranged multiple longitudinal step-by-step in the liquid to be measured;Each metal liquid level sensing probe is connected with the corresponding level input end of multiple selection and one multiple channel electronic switch, and the output end of multiple selection and one multiple channel electronic switch is connected with the input end of the detection non-conductive or conductive liquid level detection device, and the corresponding switch is gated by computer detection control device Mcu scanning multiple channel switch address, whether the metal liquid level sensing probe detects the liquid signal to be measured is judged, and the liquid level of the liquid to be measured is determined.

[0025] Further, the liquid to be measured includes liquid grease.

[0026] Compared with prior art, the utility model has the beneficial effects as follows: the metal sensing probe in suspension forms a detection loop with the medium with different dielectric constants contained in the container and the ground, and the medium that can be detected is conductive or non-conductive liquid containing low conductivity water, or air, according to the different ways of circuit output signal, the waveform is different, so as to distinguish whether the water exceeds or submerges the water level probe to determine the water level height, effectively solve the problem that the traditional electrode type liquid level detection sensor cannot be detected and the accuracy is easy to fail or even cannot be detected due to the fact that pure water cannot conduct electricity, and the stainless steel material cannot be electrolyzed and rusted, and can be wrapped by water scale to cause failure, and only needs to open installation hole at the container during installation, so that installation is convenient and fast, and the cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a kind of sensor structure schematic diagram of the utility model embodiment for detecting non-conductive or conductive liquid level;

[0028] Figure 2 It is a kind of structure schematic diagram of the liquid level detection device of the utility model embodiment for detecting non-conductive or conductive liquid level;

[0029] Figure 3 It is the internal structure schematic diagram of NE555 chip;

[0030] Figure 4 It is the triangular waveform signal generated at C, D point of the common end of high threshold trigger end THR and low threshold trigger end TR of NE555DR chip when water level probe does not contact water;

[0031] Figure 5 It is the square waveform signal generated at output end A, B point of NE555DR chip when water level probe does not contact water;

[0032] Figure 6is the filtered signal generated at the C, D point of the common end of the high threshold trigger end THR and the low threshold trigger end TR of the NE555DR chip when the water level probe contacts water;

[0033] Figure 7 is the low level signal filtered from the output signal of pin 3 of the NE555 when the water level probe contacts water;

[0034] Figure 8 is the high level signal filtered from the output signal of pin 3 of the NE555 when the water level probe contacts water;

[0035] Figure 9 is a flowchart of whether the high and low water level probes have water detected by the liquid level detection device; wherein the judgment threshold of V1, V2 can be preset;

[0036] Figure 10 is a circuit structure schematic diagram of a sensor provided by an embodiment of the utility model;

[0037] Figure 11 is a flowchart of whether multiple water level detection points have water detected by the sensor provided by an embodiment of the utility model. DETAILED DESCRIPTION

[0038] The conception, specific structure and generated technical effects of the utility model will be clearly and completely described below in combination with embodiments and drawings, so as to fully understand the purpose, scheme and effect of the utility model. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0039] Referring to Figure 1 is a structure schematic diagram of a sensor for detecting the liquid level of non-conductive or conductive liquid provided by an embodiment of the utility model. The sensor comprises a multi-vibrator driven by a direct current power supply, an oscillation / stop oscillation control end and a vibrator signal output end are arranged on the multi-vibrator, and a metal liquid level sensing probe is connected to the oscillation / stop oscillation control end. When the measured liquid level reaches or exceeds the height of the metal liquid level sensing probe, the multi-vibrator stops oscillation, and the vibrator signal output end outputs a high level or a low level. When the measured liquid level is lower than the height of the metal liquid level sensing probe during use, the multi-vibrator self-excited oscillation, and the vibrator signal output end outputs a non-steady square wave pulse signal, which constitutes a digital voltage signal output end, so as to identify the height position of the liquid level.

[0040] The time base circuit of the multi-vibrator is the time base circuit of the NE555DR, the high threshold trigger end THR and the low threshold trigger end TR are connected in parallel as the signal input end to constitute the oscillation / stop oscillation control end, and the signal output end is the out pin to constitute the vibrator signal output end.

[0041] The metal liquid level sensing probe is a contact sensing probe, specifically a water level (metal) probe. The water level probe is actually a small metal rod. The signal output end of the water level probe is connected to the input end of the oscillation / stop oscillation control end. The water level probe is insulated from the container wall, wherein the container wall is entirely metal and connected to ground. Alternatively, the container wall is partially metal, such as a kettle with a glass circumferential wall and a metal bottom wall connected to ground and serving as a contact heating disc. The water level probe and the metal material inner wall of the container form a capacitor structure.

[0042] Alternatively, the container wall is made of a non-conductive material, such as a ceramic inner wall. A metal ring is extended into the container interior through a hole in the bottom wall, and a ground wire is led out of the container. The water level probe is extended out of the hole in the circumferential wall and is water-tight. The water level probe and the metal ring form a capacitor structure.

[0043] Grounding is used to prevent water in the container wall from leaking electricity and to form a loop for the capacitor structure.

[0044] When the water level probe is not in contact with water, the water level probe and the container wall form a capacitor with air as the medium. It can be understood that air is a non-conductive medium and generally does not have the ability to charge a capacitor. There is no charge between the water level probe and the container wall, and the water level probe is suspended, with no input signal. The oscillation circuit inside the NE555DR chip generates an oscillation signal, and the output signal at pin 3 of the OUT output end of the NE555DR chip, i.e., the signal at point A, is a non-steady-state square wave pulse signal, as shown in Figure 5 .

[0045] When the water level probe is in contact with water, the water level probe and the metal part of the container wall form a capacitor with water as the medium. The output signal is input to the common end of the high threshold trigger end THR and the low threshold trigger end TR of the NE555DR chip. The oscillation circuit inside the NE555DR chip stops generating an oscillation signal, and the output signal at pin 3 of the OUT output end of the NE555DR chip, i.e., the signal at point A, is a high or low level signal after filtering, as shown in Figure 7 、 Figure 8 .

[0046] This embodiment forms a capacitor structure with the water level probe and the metal inner wall (or metal ring) of the container. The output signal obtained using the dielectric material change comparison, such as air dielectric material, is different from the output signal of pure water with low conductivity, thereby determining whether pure water reaches the water level probe based on different signals. The liquid level height position is determined based on the water level probes arranged at different heights in the container. Thus, the liquid level height of various conductive and low-conductivity pure water can be measured.

[0047] Based on the above embodiment, two high-voltage porcelain capacitors C2 and C3 are connected in series between the oscillation / stop oscillation control end and the metal liquid level sensing probe. In this scheme, the high-voltage porcelain capacitors C2 and C3 are used to isolate the 220V high-voltage when the water level probe contacts water and the water leaks electricity, so as to protect the upper computer circuit. If the circuit board of the upper computer leaks electricity, the two capacitors can ensure that the water in the container is not electrified, avoid human contact with the electrified water, and thus realize bidirectional protection.

[0048] The trigger capacitors C2 and C3 can be strong or weak electricity, and the trigger capacitors can be selected to be greater than 220V, 400V, 800V, or 1000V. With the increase of the rated voltage, the volume of the capacitor becomes larger. In some narrow installation space requirements, for example, an electric kettle, two small capacitors C2 and C3 can be connected in series to reduce the volume, so as to solve the installation space problem of the high / low voltage safety isolation circuit with the smallest space.

[0049] Based on the above embodiment, a resistance-capacitance filter circuit R1, C1 is connected to the oscillator signal output end to form an output analog voltage signal output end. This scheme can filter out noise and smooth the voltage of the output signal. Referring to Figure 1 , when the water level probe contacts or exceeds water, the resistance-capacitance filter makes the output signal of the OUT pin 3 (point A) of the NE555DR chip filtered, and a smooth signal at MCU-IO1 is obtained. According to the parameters of the resistance-capacitance filter circuit components R1, C1, and R3, the signal at point A can be filtered and smoothed to a high-level signal at MCU-IO1, referring to Figure 8 ; or the signal at point A can be filtered and smoothed to a low-level signal at MCU-IO1, referring to Figure 7 .

[0050] Based on the above embodiment, a computer detection control device Mcu corresponding to a specific application can be connected to the digital voltage signal output end. In this scheme, the computer detection control device Mcu can record the initial state and the current state of the water level probe, and compare and calculate the current signals of multiple water level probes to determine the high and low positions of the water level in the container. The computer detection control device Mcu includes an embedded or single-chip computer, and a digital signal input interface or an analog / digital conversion interface A / D of the computer is connected to the digital voltage signal output end or the analog voltage signal output end.

[0051] Based on the above embodiment, the non-conductive liquid is pure water or distilled water, pure water with poor conductivity, and spring water, tap water, and ultrafiltration water containing conductive substances. In this scheme, compared with ordinary tap water, mineral water and other mineral-rich water can be used as a conductive medium, so that the water level probe can detect the electric signal. However, pure water or distilled water does not exist as a conductive medium. By contacting the inductive probe as a metal liquid level inductive probe, the dielectric constant of the water level probe and the container wall is different, for example, the dielectric constant of air is different from that of pure water or distilled water. Different output signals and waveforms are measured to distinguish whether the liquid level reaches the water level probe. According to the water level probes arranged at different heights in the container, the liquid level height position is determined.

[0052] Based on the above embodiment, the multivibrator is a typical astable multivibrator composed of two triodes and resistance, capacitance circuits. The output end of an optional triode is used as the oscillator signal output end, and the self-oscillation control end is connected with the metal liquid level inductive probe.

[0053] Based on the above embodiment, the computer is used for: (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 is determined that the liquid level reaches or exceeds the position of the metal liquid level inductive probe at this time. When the corresponding digital signal input interface of the computer detects that the received signal is a pulse oscillation signal, it is determined that the liquid level is lower than the position of the metal liquid level inductive probe at this time.

[0054] (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 is determined that the liquid level reaches or exceeds the position of the metal liquid level inductive probe at this time. 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 or low voltage, it is determined that the liquid level is lower than the position of the metal liquid level inductive probe at this time.

[0055] Referring to Figure 2This 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 this utility model. 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 water jug ​​is used as an example. Due to the limited space of the water jug, the inner wall of the jug 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 jug. The water level probe and the inner wall of the jug form a capacitor structure. Optionally, the water level probe is insulated from the jug; the circumferential wall of the jug 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.

[0056] Optionally, the kettle wall is made of a non-conductive material, such as a container with an entirely ceramic inner wall. A hole is drilled in the bottom wall of the container to create a water seal, and a metal ring extends 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.

[0057] Grounding is used to prevent water leakage from the container wall and to form a circuit for the capacitor structure.

[0058] 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.

[0059] C3, C4, C5, C6: 10pF~100nF

[0060] C1, C2:nF~1Uf

[0061] R1, R2, R3, R4, R5, R6: 1kΩ~100MΩ

[0062] C3, C4, C5, C6 are high-voltage ceramic capacitor, filter, strong electric isolation.

[0063] R3, R5 are pull-down resistors.

[0064] R4, R6 are current limiting resistors, R1 and C1, R2 and C2 form RC filter circuit, so that the effective average voltage value of square wave signal output of A point, B point, the greater the R, the more stable the voltage.

[0065] MCU-IO1 and MCU-IO2 are set to analog input mode, detect voltage value, the kettle body is connected to GND.

[0066] The multivibrator NE555 chip in the embodiment can be replaced by NE556 chip.

[0067] Referring to Figure 3 , it is an internal structure diagram of NE555 chip. The input voltage Va at the high threshold trigger end THR of NE555 chip, the input voltage Vb at the low threshold trigger end TR. NE555 chip mainly consists of three parts: voltage divider circuit, voltage comparator, RS trigger; the voltage divider circuit is used for providing voltage comparator comparison voltage; the voltage comparator is used for outputting high and low level according to trigger signal; the RS trigger is used for outputting rectangular wave.

[0068] Combined with Figure 2 and Figure 3 , the input voltage of NE555 chip, input and output logic are as follows table 1, table 2:

[0069] Table 1

[0070] Va Vb R S Q > 2 / 3 Vcc > 1 / 3 Vcc 0 1 0 <2 / 3Vcc > 1 / 3 Vcc 1 1 Hold <2 / 3Vcc <1 / 3Vcc 1 0 1

[0071] Table 2

[0072] Va = Vb R S Q 0V 1 0 1 > 1 / 3 Vcc 1 1 Hold > 2 / 3 Vcc 0 1 0 <2 / 3Vcc 1 1 Hold <1 / 3Vcc 1 0 1

[0073] When the kettle has no water, C3, C4, R3 and C5, C6, R5 are in suspended state, when NE555 timer works, C point and D point will produce a triangular wave signal as Figure 4When C=0, D=0, A, B point output 1; when C>1 / 3Vcc, D>1 / 3Vcc, A, B point keep original state, still output 1; when C>2 / 3Vcc, D>2 / 3Vcc, A, B point output 0, level produces flip; when C<2 / 3Vcc, D(2 / 3Vcc, A, B point keep original state, still output 0; when C<1 / 3Vcc, D<1 / 3Vcc, A, B point output 1, level produces flip. A, B point will output a square wave signal such as Figure 5 , square wave signal frequency is about 50HZ, duty cycle is about 1 / 2, MCU-I01 and MCU-I02 pin measured voltage value is about 1 / 2VCC.

[0074] When there is water in the kettle, and higher than the water level probe, the water level probe and the metal kettle wall equivalent to a water capacitor connected to GND, C3, C4, R3 and C5, C6, R5 can filter signal such as Figure 6 , so that the C point and D point voltage value is small. When C<1 / 3Vcc, D<1 / 3Vcc, A, B point output 1; when C>2 / 3Vcc, D>2 / 3Vcc, A, B point output 0; when 1 / 3Vcc<C<2 / 3Vcc, 1 / 3Vcc<D<2 / 3Vcc, A, B point is to keep the original state, C point or D point voltage is from less than 1 / 3Vcc to more than 1 / 3Vcc less than 2 / 3Vcc, A, B point output 1, C point or D point voltage is from more than 2 / 3Vcc to less than 2 / 3Vcc more than 1 / 3Vcc, A, B point output 0, so the pin 3 of NE555 output signal such as Figure 7 or such as Figure 8 signal, MCU-IO1 and MCU-IO2 pin measured voltage value is about 0 or VCC. Thus can know the high and low state of the kettle.

[0075] Referring to Figure 2 , when the water level probe contacts or exceeds the water, due to the resistance and capacitance filter, the signal at the output end OUT pin 3 (A point) of the NE555 DR chip U2 is filtered, and a stable signal at MCU-IO1 is obtained; according to the parameters of the resistance and capacitance filter circuit components R1, C1, R6, the signal at A point can be filtered and stabilized as a high level signal at MCU-IO1, see Figure 8 ; the signal at A point can also be filtered and stabilized as a low level signal at MCU-IO1, see Figure 7 . Similarly, according to the parameters of the resistance and capacitance filter circuit components R2, C2, R4, the signal at B point can be filtered and stabilized as a high level signal at MCU-IO2, see Figure 8 ; the signal at B point can also be filtered and stabilized as a low level signal at MCU-IO2, see Figure 7.

[0076] Referring to Figure 9 , the voltage of VCC is set to 5V, the threshold for determining whether there is water is 1.5V, and the threshold for determining whether there is water is 3.5V; the actual voltage V1 of the MCU-IO2 pin (high water level) is measured, if V1 < 1.5V, the high water level has water, and the output signal diagram is shown in Figure 7 , if V1 > 3.5V, the high water level has water, and the output signal diagram is shown in Figure 8 ; when 1.5 < V1 < 3.5V, the high water level has no water. The low water level determination method is the same.

[0077] , the threshold is , the low voltage threshold of the signal at MCU-IO1 after resistance-capacitance filtering is , the high voltage threshold of the signal at MCU-IO1 after resistance-capacitance filtering is.

[0078] In this embodiment, the water level probe and the inner wall of the kettle form a capacitor structure, and the output signals obtained by the dielectric material changes of the capacitor, such as air dielectric material, are different from the output signals of pure water dielectric material, so that whether the water level probe is submerged or contacted by the water in the kettle is determined according to different signals, and the position of the liquid in the kettle is determined by combining the output signals of the high and low water level probes.

[0079] The utility model embodiment provides a kind of electric appliance, and the liquid level detection device of the embodiment of detecting non-conductive or conductive liquid level is internally arranged.The electric appliance can be electric kettle, electric tea stove, water dispenser, water purifier.The high water level probe and low water level probe of the liquid level detection device of detecting non-conductive or conductive liquid level are arranged on the inner wall of the electric appliance kettle, the metal bottom wall of the electric appliance kettle or the metal ring of the bottom wall of the insulating material is grounded, and the water level detection circuit and computer detection control device Mcu chip are arranged in the host part of the electric appliance, and the specific embodiment is as described in the device embodiment, which will not be repeated here.

[0080] Referring to Figure 10 , it is a kind of circuit structure schematic diagram of liquid level sensor provided by the utility model embodiment, and the sensor includes the liquid level detection device made of the method of detecting non-conductive or conductive liquid level, wherein the metal liquid level sensing probe is 5 water level probes and is vertically arranged in the bucket. One water level probe is grounded, and the other 4 water level probes are respectively connected to the input end of one single-ended 8-channel multiplexer CD4051 chip, and one output end pin 3 of CD4051 chip is connected to water level detection circuit, wherein water level detection circuit is shown in Figure 1The output end MCU-IO1 of the water level detection circuit is connected to the input end pin 5 of the computer detection control device U3-NY8B062FS8.

[0081] The water bucket is made of non-conductive material, and the inner wall of the water bucket is generally made of polycarbonate material.

[0082] Referring to Figure 11 The computer detection control device U3-NY8B062FS8 continuously scans the A, B and C pins of the CD4051 chip, inputs a binary address signal of 0-7 channels to the A, B and C pins to determine the gating of the corresponding switch, and obtains the signal of the water level probe connected to the corresponding switch to detect whether the water level reaches or exceeds the water level probe.

[0083] The principle of the utility model can also be used to detect the liquid level of liquid oil.

[0084] The above is only a preferred embodiment of the utility model, and the utility model is not limited to the above-mentioned implementation mode, as long as the same means is used to achieve the technical effect of the utility model, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the disclosure should be included in the protection scope of the disclosure. All should belong to the protection scope of the utility model. The technical scheme and / or implementation mode can have various modifications and changes within the protection scope of the utility model.

Claims

1. A device for detecting the level of a non-conducting or conducting liquid, characterized in that The multivibrator is driven by a direct current power supply, and an oscillation / stop oscillation control terminal and an oscillator signal output terminal are arranged on the multivibrator, and 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 sensing probe, the multivibrator stops oscillation, 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 sensing probe, the multivibrator self-excitedly oscillates, and the oscillator signal output terminal outputs a non-steady-state pulse oscillation signal, so that the output state identifies the height position of the liquid level.

2. The apparatus for detecting the level of a non-conductive or conductive liquid of claim 1, wherein, The non-conductive liquid includes non-conductive pure water, poor-conductive reverse osmosis filtered pure water and distilled water; and the conductive liquid includes water in nature, mineral water, tap water and ultra-filtered water thereof.

3. The apparatus for detecting the level of a non-conductive or conductive liquid of claim 1, wherein, The liquid is water or a water-containing liquid.

4. The apparatus for detecting the level of a non-conductive or conductive liquid of claim 1, wherein, 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 apparatus for detecting the level of a non-conductive or conductive liquid of claim 4, wherein, The trigger capacitor is a strong / weak electric isolation capacitor (C2, C3).

6. The apparatus for detecting the level of a non-conductive or conductive liquid of claim 1, wherein, The oscillator signal output terminal directly outputs a digital voltage signal output terminal (Vod); or, a resistance-capacitance filter circuit is connected to the oscillator signal output terminal to form an analog voltage signal output terminal (Voa) outputting an analog voltage signal.

7. The apparatus for detecting the level of a non-conductive or conductive liquid of claim 1, wherein, The metal liquid level sensing probe is a contact type sensing probe.

8. The device for detecting the level of a non-conductive or conductive liquid according to any one of claims 1 to 5, 7, characterized in that, The oscillator signal output terminal is a digital voltage signal output terminal (Vod) or an analog voltage signal output terminal (Voa), and a computer detection control device (Mcu) corresponding to a specific application is connected to the digital voltage signal output terminal (Vod) or the analog voltage signal output terminal (Voa), and the system ground of the direct current power supply.

9. The apparatus for detecting the level of a non-conductive or conductive liquid of claim 8, wherein, The multivibrator is composed of a 555 / 556 time base circuit, and a high threshold trigger end (THR) and a low threshold trigger end (TR) of the multivibrator are connected in parallel as a signal input terminal to form the oscillation / stop oscillation control terminal, and a signal output terminal is an out pin to form the oscillator signal output terminal.

10. The apparatus for detecting the level of a non-conductive or conductive liquid of claim 9, wherein, The pulse oscillation signal is a square wave.

11. The apparatus for detecting the level of a non-conductive or conductive liquid of claim 8, wherein, The multivibrator is a typical non-steady-state multivibrator composed of two triodes and resistance and capacitance circuits, and an output end of an optional triode is used as the oscillator signal output terminal, and the metal liquid level sensing probe is connected to a self-excitation control end of the triode.

12. The apparatus for detecting the level of a non-conductive or conductive liquid of claim 11, wherein, The pulse oscillation signal is a triangular wave or a sine wave.

13. The apparatus for detecting a level of a non-conductive or conductive liquid of claim 8, wherein, The computer detection control device (Mcu) includes an embedded or single-chip computer, and a corresponding digital signal input interface (In1) or an analog / digital conversion interface (A / D) of the computer is connected to the digital voltage signal output terminal (Vod) or the analog voltage signal output terminal (Voa) in correspondence.

14. The device for detecting the liquid level of a non-conductive or conductive liquid according to claim 13, wherein When the corresponding digital signal input interface (In1) of the computer detects that the received signal is a stable high or low level, it is determined that the liquid level reaches or exceeds the position of the metal liquid level sensing probe at this time; when the corresponding digital signal input interface (In1) of the computer detects that the received signal is a pulse oscillation signal, it is determined that the liquid level is lower than the position of the metal liquid level sensing probe at this time; or, 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 is determined that the liquid level reaches or exceeds the position of the metal liquid level sensing probe at this time; 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 or low voltage, it is determined that the liquid level is lower than the position of the metal liquid level sensing probe at this time.

15. A sensor, characterized by The device for detecting the liquid level of non-conductive or conductive liquid in any one of claims 1-14 is packaged as a sensor.

16. An electrical appliance characterised in that, The electric appliance is provided with the device in any one of claims 1-14 or the sensor in claim 15, wherein the electric appliance includes an electric kettle, an electric tea kettle, a water dispenser, a water purifier, and a boiler.

17. A liquid level sensor, characterized by The device for detecting the liquid level of non-conductive or conductive liquid in any one of claims 8-14 includes a plurality of metal liquid level sensing probes longitudinally arranged in the measured liquid, each metal liquid level sensing probe is connected to the corresponding stage input end of the multiple selection multiple channel electronic switch, the output end of the multiple selection multiple channel electronic switch is connected to the input end of the device for detecting the liquid level of non-conductive or conductive liquid, and the metal liquid level sensing probe is scanned by the computer detection control device (Mcu) to determine whether the measured liquid signal is detected, thereby determining the liquid level of the measured liquid.

18. The liquid level sensor of claim 17, wherein, The measured liquid includes liquid oil.

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