Water level detection device, method and household appliance

Abstract

The present application relates to a water level detection device, method and household appliance, wherein the water level detection device comprises: an acquisition module, a shaping and amplifying module and a control module pre-stored with a correspondence table between water level and frequency; the acquisition module is used to output an oscillation signal to the shaping and amplifying module according to the current water pressure; the shaping and amplifying module is used to differentially amplify the oscillation signal and convert the waveform into a square wave through a loop composed of a resistor, a capacitor, a voltage-stabilizing diode and an NPN-type transistor; the control module is used to detect the frequency of the square wave output by the shaping and amplifying module and obtain the actual water level according to the correspondence table between water level and frequency. The present invention uses a combination of a voltage-stabilizing diode and an NPN-type transistor to replace the complex design of a 4069 chip and its peripheral circuits to realize water level detection, thereby simplifying the design of the water level detection device and saving costs.

Description

Technical Field

[0001] The present application relates to the technical field of water level detection, and in particular to a water level detection device, method and household appliance. Background Art

[0002] With the continuous development of intelligence, the popularity of intelligence in the home appliance industry is also increasing. The functions of home appliances are becoming more and more powerful, bringing greater convenience and speed to people's lives. Some home appliances, such as washing machines and dishwashers, have water filling, water storage, and drainage functions. Water level detection and its accuracy are particularly basic and important.

[0003] During the implementation process, the inventors found that most household appliance water level detection circuits in traditional technology use 4069 chips and peripheral circuits to amplify and shape the collected signals, and then use software filtering to obtain a relatively stable number of pulses (frequency), and then transform them to obtain the actual water level value. In this way, there are at least the following problems:

[0004] 1. The circuit structure is complex, resulting in high cost;

[0005] 2. In the case of abnormal waveform level or missing waveform, the number of pulses (frequency) cannot be effectively detected, resulting in inaccurate water level detection results. Summary of the invention

[0006] The embodiments of the present application provide a water level detection device, method and household appliance to solve the problems of complex structure of existing water level detection circuits, high design difficulty and cost, and inaccurate water level detection results, simplify the design of the water level detection device and reduce costs, while improving the stability and reliability of water level detection.

[0007] In order to achieve the above-mentioned purpose, on the one hand, an embodiment of the present application provides a water level detection device, including: a collection module, a shaping and amplification module, and a control module pre-stored with a correspondence table between water level and frequency;

[0008] The acquisition module is used to output an oscillation signal to the shaping and amplification module according to the current water pressure;

[0009] The shaping and amplifying module is used to differentially amplify the oscillating signal and convert the waveform into a square wave; the shaping and amplifying module includes a differential amplifier, a first resistor, a second resistor, a first capacitor, a second capacitor, a voltage regulator diode and an NPN transistor; wherein,

[0010] The input end and the output end of the differential amplifier are respectively connected to the output end of the acquisition module and one end of the first resistor, the other end of the first resistor is connected to one end of the first capacitor, the other end of the first capacitor is respectively connected to the cathode of the voltage zener diode and the base of the NPN transistor, the emitter of the NPN transistor is respectively connected to the anode of the voltage zener diode and one end of the second capacitor and is grounded, and the collector of the NPN transistor is respectively connected to one end of the second resistor, the other end of the second capacitor and the input end of the control module;

[0011] The control module is used to detect the frequency of the square wave output by the shaping and amplifying module, and obtain the actual water level according to the corresponding relationship table between the water level and the frequency.

[0012] In one of the embodiments, the control module includes a filtering unit, a counting unit and a query unit;

[0013] The filtering unit is used to monitor the level jump time of the square wave and filter out the square wave whose level jump time is less than the first preset time;

[0014] The counting unit is used to count the square wave filtered by the filtering unit within a second preset time to obtain the frequency of the square wave;

[0015] The query unit is used to query the corresponding relationship table between water level and frequency pre-stored locally according to the frequency of the square wave to obtain the actual water level.

[0016] In one of the embodiments, the control module further includes a delay unit;

[0017] The delay unit is used to delay the detection action of the frequency of the square wave output by the shaping and amplifying module by a preset third time.

[0018] In one of the embodiments, the first preset time is the product of 1 / 2 period of the square wave and the filter coefficient.

[0019] In one of the embodiments, 1 / 2 period of the square wave is 1 / 2 period of the square wave of maximum frequency, and the filter coefficient is less than 0.5.

[0020] In one of the embodiments, the acquisition module is a pressure water level sensor.

[0021] On the other hand, the embodiment of the present application further provides a water level detection method, comprising:

[0022] Collect the oscillation signal corresponding to the current water pressure;

[0023] The oscillation signal is differentially amplified by a shaping amplifier circuit and the waveform is converted into a square wave; wherein the shaping amplifier circuit includes a differential amplifier, a first resistor, a second resistor, a first capacitor, a second capacitor, a voltage regulator diode and an NPN transistor; wherein,

[0024] The output end of the differential amplifier is connected to one end of the first resistor, the other end of the first resistor is connected to one end of the first capacitor, the other end of the first capacitor is respectively connected to the cathode of the voltage zener diode and the base of the NPN transistor, the emitter of the NPN transistor is respectively connected to the anode of the voltage zener diode and one end of the second capacitor and is grounded, and the collector of the NPN transistor is respectively connected to one end of the second resistor and the other end of the second capacitor;

[0025] The frequency of the square wave is detected, and the actual water level is obtained according to the local pre-stored correspondence table between water level and frequency.

[0026] In one embodiment, the detecting the frequency of the square wave and obtaining the actual water level according to a locally pre-stored correspondence table between water level and frequency includes:

[0027] Monitoring the level jump time of the square wave, and filtering out the square wave whose level jump time is less than the first preset time;

[0028] Counting the square wave filtered by the filtering unit within a second preset time to obtain the frequency of the square wave;

[0029] According to the frequency of the square wave, the local pre-stored correspondence table between water level and frequency is queried to obtain the actual water level.

[0030] In one of the embodiments, the first preset time is the product of 1 / 2 period of the square wave and the filter coefficient.

[0031] On the other hand, an embodiment of the present application further provides a household appliance, comprising the water level detection device as described above.

[0032] The present invention has the following advantages and beneficial effects:

[0033] In view of the problem that the existing water level detection circuit has a complex structure, is difficult to design and has a high cost, one of the above technical solutions replaces the complex design of the 4069 chip and its peripheral circuits with a circuit composed of a first resistor, a second resistor, a first capacitor, a second capacitor, a voltage-stabilizing diode and an NPN transistor to achieve water level detection, thereby simplifying the design of the water level detection device and saving costs. On the other hand, in view of the problem that the water level detection result is inaccurate, one of the above technical solutions effectively avoids the situation that the number of pulses (frequency) cannot be effectively detected due to abnormal waveform level or missing waveform during square wave counting by setting a filtering time, thereby improving the stability and reliability of water level detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic structural diagram of a water level detection device provided for one embodiment of the present application.

[0035] Figure 2 A schematic structural diagram of a water level detection device provided for one embodiment of the present application.

[0036] Figure 3 for Figure 1 or Figure 2 Schematic diagram of the square wave detected by the control module.

[0037] Figure 4 A schematic structural diagram of a water level detection device provided for one embodiment of the present application.

[0038] Figure 5 A schematic structural diagram of a water level detection device provided for one embodiment of the present application.

[0039] Figure 6 A schematic flow chart of a water level detection method provided for one embodiment of the present application.

[0040] Figure 7 A schematic flow chart of a water level detection method provided for one embodiment of the present application.

[0041] Figure 8 A schematic flow chart of a water level detection method provided for one embodiment of the present application. DETAILED DESCRIPTION

[0042] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0043] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to another element and integrated therewith, or there may be an intermediate element at the same time. The terms "installed", "one end", "the other end" and similar expressions used herein are for illustrative purposes only.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0045] The camera posture method, device, computer equipment and storage medium provided by the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0046] In one embodiment, Figure 1-2 As shown, a water level detection device is provided, comprising: an acquisition module 1, a shaping and amplification module 2, and a control module 3 which pre-stores a corresponding relationship table between water level and frequency.

[0047] The acquisition module 1 is used to output an oscillation signal to the shaping and amplification module 2 according to the current water pressure.

[0048] Exemplarily, the acquisition module 1 is a pressure-type water level sensor, including an inductor 11 and a third capacitor 12. The pressure-type water level sensor generates different air pressures due to the water level, which in turn affects the internal inductor 11, so that the resonant frequency also changes. In this way, the pressure-type water level sensor can accurately output an oscillation signal according to the current water pressure.

[0049] The shaping and amplifying module 2 is used to differentially amplify the oscillating signal and convert the waveform into a square wave. The shaping and amplifying module 2 includes a differential amplifier 21, a first resistor 22, a second resistor 26, a first capacitor 23, a second capacitor 27, a voltage stabilizing diode 24 and an NPN transistor 25.

[0050] Among them, the input end and the output end of the differential amplifier 21 are respectively connected to the output end of the acquisition module 1 and one end of the first resistor 22, the other end of the first resistor 22 is connected to one end of the first capacitor 23, the other end of the first capacitor 23 is respectively connected to the cathode of the voltage-stabilizing diode 24 and the base of the NPN transistor 25, the emitter of the NPN transistor 25 is respectively connected to the anode of the voltage-stabilizing diode 24 and one end of the second capacitor 27 and grounded, and the collector of the NPN transistor 25 is respectively connected to one end of the second resistor 26, the other end of the second capacitor 27 and the input end of the control module 3.

[0051] In the prior art, a 4069 chip is usually used to connect to a pressure-type water level sensor. The difference in air pressure is generated by the height of the water level, thereby changing the internal inductance 11 and the frequency of the oscillation circuit. The 4069 chip and the peripheral circuit are inverted, amplified, and shaped, and finally output to the control system, which collects square waves and determines the height of the water level according to the change in frequency. This method causes the structural design of the water level detection device to become complicated and the design cost is relatively large. For this reason, in the present embodiment, the loop composed of the first resistor 22, the second resistor 26, the first capacitor 23, the second capacitor 27, the voltage-stabilizing diode 24 and the NPN transistor 25 replaces the complex design of the 4069 chip and its peripheral circuit to realize water level detection, thereby simplifying the design of the water level detection device and saving costs.

[0052] Exemplarily, in addition to the pressure-type water level sensor that outputs the collectable signal, the hardware circuit also includes a first capacitor 23, a first resistor 22, a voltage-stabilizing diode 24, an NPN transistor 25, a second resistor 26, and a second capacitor 27. The pressure-type water level sensor generates a sine wave with a frequency f and an amplitude V1 through different water levels, and after passing through the differential amplifier 21, it becomes a sine wave with a frequency f and an amplitude V1. After the sine wave passes through the loop formed by the first resistor 22, the first capacitor 23 and the Zener diode 24, when the amplitude V1 is greater than 0 and greater than the breakdown voltage VDR1 of the Zener diode 24, the amplitude V1 is clamped to the voltage VDR1. When VDR1 is greater than the VBE conduction voltage of the NPN transistor 25, the NPN transistor 25 is turned on, and the control module 3 can detect a low level. When the amplitude V1 is less than 0 and the value is greater than the conduction voltage VDF1 of the Zener diode 24, the base voltage of the NPN transistor 25 is clamped to -VDF1, the NPN transistor 25 is turned off, and the control module 3 can detect a high level. In this way, the control module 3 can detect a square wave with a frequency of f, where the waveform of the square wave is as follows: Figure 3 shown.

[0053] The control module 3 is configured to detect the frequency of the square wave output by the shaping and amplifying module 2, and obtain the actual water level according to the corresponding relationship table between the water level and the frequency.

[0054] As Figure 4 shown, in one embodiment, the control module 3 includes a filtering unit, a counting unit, and a query unit;

[0055] The filtering unit is configured to monitor the level transition time of the square wave and filter out the square wave whose level transition time is less than a first preset time;

[0056] The counting unit is configured to count the square wave filtered by the filtering unit within a second preset time to obtain the frequency of the square wave;

[0057] The query unit is configured to query the corresponding relationship table between the water level and the frequency pre-stored locally according to the frequency of the square wave to obtain the actual water level.

[0058] As Figure 5 shown, in one embodiment, the control module 3 further includes a delay unit;

[0059] The delay unit is configured to delay the detection action of the frequency of the square wave output by the shaping and amplifying module 2 by a preset third time.

[0060] Exemplarily, the control module 3 is an MCU (Motor Control Unit, i.e., motor controller) loaded with relevant software algorithms. After the control module 3 detects a square wave with a frequency of f, the control module 3 is initialized after power-on and performs the detection action of the frequency of the square wave after initialization. Therefore, the control module 3 delays for t0, and it is known in advance that the water level frequency range is f0~f1 (according to the specification provided by the manufacturer), where f0 < f < f1, and the minimum value t1 of half of the square wave period can be obtained.

[0061] The control module 3 counts the detected square wave and monitors the level transition time of the square wave. When monitoring and timing during the level conversion, if the level conversion interval time is less than nt1, where n is the filtering coefficient and n < 0.5, no counting is performed, otherwise the count is incremented by 1. The control module 3 continuously counts until the duration t2 to obtain the water level frequency f2. Query the corresponding relationship table between the water level frequency and the water level to determine the actual water level height and perform subsequent processing.

[0062] The above embodiment effectively avoids the situation where the pulse number (frequency) cannot be effectively detected due to abnormal waveform level or waveform missing during the square wave counting process by setting the filtering time, improving the stability and reliability of water level detection.

[0063] In one of the embodiments, the first preset time is the product of 1 / 2 period of the square wave and the filter coefficient.

[0064] The filtering time needs to be adjusted according to the circuit disturbance. For example, when the first preset time is 1 / 2 cycle of the square wave, the practicality of this implementation is higher and the implementation cost is lower.

[0065] In one of the embodiments, 1 / 2 period of the square wave is 1 / 2 period of the square wave of maximum frequency, and the filter coefficient is less than 0.5.

[0066] like Figure 3 As shown, the control module 3 can detect the square wave signal converted by the water level height, but there will also be resonance interference. The software loaded by the control module 3 performs the next step of filtering to ensure the accuracy of the water level parameters. According to the specification provided by the water level sensor supplier, the measurable water level frequency range is obtained, that is, the actual frequency range of the square wave is determined, and then the square wave half cycle t1 of the maximum frequency is determined. The filter coefficient n (n<0.5) is introduced. Thereby avoiding the situation in which the number of pulses (frequency) cannot be effectively detected due to abnormal waveform level or missing waveform during square wave counting, and improving the stability and reliability of square wave counting.

[0067] On the other hand, Figure 6 As shown, the embodiment of the present application also provides a water level detection method, including:

[0068] S1. Collect the oscillation signal corresponding to the current water pressure.

[0069] Exemplarily, the acquisition module 1 is a pressure water level sensor. The pressure water level sensor generates different air pressures due to the water level, which in turn affects the internal inductor 11, so that the resonant frequency will also change. In this way, the pressure water level sensor can accurately output an oscillation signal according to the current water pressure.

[0070] S2. The oscillation signal is differentially amplified by a shaping amplifier circuit and the waveform is converted into a square wave; wherein the shaping amplifier circuit includes a differential amplifier 21, a first resistor 22, a second resistor 26, a first capacitor 23, a second capacitor 27, a voltage regulator diode 24 and an NPN transistor 25.

[0071] Among them, the output end of the differential amplifier 21 is connected to one end of the first resistor 22, the other end of the first resistor 22 is connected to one end of the first capacitor 23, the other end of the first capacitor 23 is respectively connected to the cathode of the voltage-stabilizing diode 24 and the base of the NPN transistor 25, the emitter of the NPN transistor 25 is respectively connected to the anode of the voltage-stabilizing diode 24 and one end of the second capacitor 27 and grounded, and the collector of the NPN transistor 25 is respectively connected to one end of the second resistor 26 and the other end of the second capacitor 27.

[0072] In the prior art, a 4069 chip is usually used to connect to a pressure-type water level sensor. The difference in air pressure is generated by the height of the water level, thereby changing the internal inductance 11 and the frequency of the oscillation circuit. The 4069 chip and the peripheral circuit are inverted, amplified, and shaped, and finally output to the control system, which collects square waves and determines the height of the water level according to the change in frequency. This method causes the structural design of the water level detection device to become complicated and the design cost is relatively large. For this reason, in the present embodiment, the loop composed of the first resistor 22, the second resistor 26, the first capacitor 23, the second capacitor 27, the voltage-stabilizing diode 24 and the NPN transistor 25 replaces the complex design of the 4069 chip and its peripheral circuit to realize water level detection, thereby simplifying the design of the water level detection device and saving costs.

[0073] like Figure 2 As shown, the hardware circuit, in addition to the pressure-type water level sensor that outputs the collectable signal, also includes a first capacitor 23, a first resistor 22, a voltage-stabilizing diode 24, an NPN transistor 25, a second resistor 26, and a second capacitor 27. The pressure-type water level sensor generates a sine wave with a frequency f and an amplitude V1 through different water levels due to different internal inductance 11; after passing through the differential amplifier 21, it becomes a sine wave with a frequency f and an amplitude V1. After the sine wave passes through the loop formed by the first resistor 22, the first capacitor 23 and the Zener diode 24, when the amplitude V1 is greater than 0 and greater than the breakdown voltage VDR1 of the Zener diode 24, the amplitude V1 is clamped to the voltage VDR1. When VDR1 is greater than the VBE conduction voltage of the NPN transistor 25, the NPN transistor 25 is turned on, and the control module 3 can detect a low level. When the amplitude V1 is less than 0 and the value is greater than the conduction voltage VDF1 of the Zener diode 24, the base voltage of the NPN transistor 25 is clamped to -VDF1, the NPN transistor 25 is turned off, and the control module 3 can detect a high level. In this way, the control module 3 can detect a square wave with a frequency of f, where the waveform of the square wave is as follows: Figure 3 shown.

[0074] S3. Detect the frequency of the square wave and obtain the actual water level according to the corresponding relationship table between water level and frequency pre-stored locally.

[0075] As Figure 7 shown, in one embodiment, detecting the frequency of the square wave and obtaining the actual water level according to the correspondence table of water level and frequency pre-stored locally includes:

[0076] S31. Monitoring the level jump time of the square wave and filtering out the square waves with a level jump time less than a first preset time;

[0077] S32. Counting the square waves filtered by the filtering unit within a second preset time to obtain the frequency of the square wave;

[0078] S33. Querying the correspondence table of water level and frequency pre-stored locally according to the frequency of the square wave to obtain the actual water level.

[0079] As Figure 8 shown, in one embodiment, detecting the frequency of the square wave and obtaining the actual water level according to the correspondence table of water level and frequency pre-stored locally further includes:

[0080] S30. Delaying the detection action of the frequency of the square wave output by the shaping and amplifying module 2 by a preset third time.

[0081] Exemplarily, the control module 3 is an MCU (Motor Control Unit, i.e., motor controller) loaded with relevant software algorithms. After the control module 3 can detect the square wave with a frequency of f, the control module 3 is initialized after power-on and performs the detection action of the frequency of the square wave after initialization. Therefore, the control module 3 delays for t0, and the water level frequency range f0~f1 (according to the specification provided by the manufacturer) is known in advance, where f0 < f < f1, and the minimum value t1 of half of the square wave period can be obtained.

[0082] The control module 3 counts the detected square waves and monitors the level jump time of the square waves. Monitoring and timing are performed during the level conversion. If the level conversion interval time is less than nt1, where n is the filtering coefficient and n < 0.5, no counting is performed, otherwise the count is incremented by 1. The control module 3 continuously counts until the duration t2 to obtain the water level frequency f2. Query the correspondence table of water level frequency and water level to determine the actual water level height and perform subsequent processing.

[0083] The above embodiment effectively avoids the situation where the number of pulses (frequency) cannot be effectively detected due to abnormal waveform levels or waveform loss during the square wave counting process by setting the filtering time, improving the stability and reliability of water level detection.

[0084] In one embodiment, the first preset time is the product of half of the square wave period and the filtering coefficient.

[0085] The filtering time needs to be adjusted according to the circuit disturbance. For example, when the first preset time is 1 / 2 cycle of the square wave, the practicality of this implementation is higher and the implementation cost is lower.

[0086] In one of the embodiments, 1 / 2 period of the square wave is 1 / 2 period of the square wave of maximum frequency, and the filter coefficient is less than 0.5.

[0087] like Figure 3 As shown, the control module 3 can detect the square wave signal converted by the water level height, but there will also be resonance interference. The software loaded by the control module 3 performs the next step of filtering to ensure the accuracy of the water level parameters. According to the specification provided by the water level sensor supplier, the measurable water level frequency range is obtained, that is, the actual frequency range of the square wave is determined, and then the square wave half cycle t1 of the maximum frequency is determined. The filter coefficient n (n<0.5) is introduced. Thereby avoiding the situation in which the number of pulses (frequency) cannot be effectively detected due to abnormal waveform level or missing waveform during square wave counting, and improving the stability and reliability of square wave counting.

[0088] On the other hand, an embodiment of the present application further provides a household appliance, comprising the water level detection device as described above.

[0089] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0090] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A water level detection device, characterized in that: It includes an acquisition module, a shaping and amplification module, and a control module pre-stored with a corresponding relationship table between water level and frequency; The acquisition module is used to output an oscillation signal to the shaping and amplifying module according to the current water pressure. The acquisition module is a pressure-type water level sensor including an inductor and a third capacitor; The shaping and amplifying module is used to differentially amplify the oscillating signal and convert the waveform into a square wave; the shaping and amplifying module includes a differential amplifier, a first resistor, a second resistor, a first capacitor, a second capacitor, a voltage regulator diode and an NPN transistor; wherein, The input end and the output end of the differential amplifier are respectively connected to the output end of the acquisition module and one end of the first resistor, the other end of the first resistor is connected to one end of the first capacitor, the other end of the first capacitor is respectively connected to the cathode of the voltage zener diode and the base of the NPN transistor, the emitter of the NPN transistor is respectively connected to the anode of the voltage zener diode and one end of the second capacitor and is grounded, and the collector of the NPN transistor is respectively connected to one end of the second resistor, the other end of the second capacitor and the input end of the control module; The voltage regulator diode is also used to control the NPN transistor to output a corresponding square wave according to the waveform output by the differential amplifier; wherein, after the waveform passes through the loop formed by the first resistor, the first capacitor and the voltage regulator diode, when the amplitude of the waveform is greater than 0 and greater than the breakdown voltage of the voltage regulator diode, the amplitude of the waveform is clamped to the breakdown voltage of the voltage regulator diode, and when the breakdown voltage of the voltage regulator diode is greater than the conduction voltage of the base and emitter of the NPN transistor, the NPN transistor is turned on; when the amplitude of the waveform is less than 0 and the value is greater than the conduction voltage of the voltage regulator diode, the base voltage of the NPN transistor is clamped to the negative conduction voltage of the voltage regulator diode, and the NPN transistor is turned off; The control module is used to detect the frequency of the square wave output by the shaping and amplifying module, and obtain the actual water level according to the corresponding relationship table between the water level and the frequency.

2. The water level detection device according to claim 1, characterized in that: The control module includes a filtering unit, a counting unit and a query unit; The filtering unit is used to monitor the level jump time of the square wave and filter out the square wave whose level jump time is less than the first preset time; The counting unit is used to count the square wave filtered by the filtering unit within a second preset time to obtain the frequency of the square wave; The query unit is used to query the corresponding relationship table between water level and frequency pre-stored locally according to the frequency of the square wave to obtain the actual water level.

3. The water level detection device according to claim 2, characterized in that: The control module further includes a delay unit; The delay unit is used to delay the detection action of the frequency of the square wave output by the shaping and amplifying module by a preset third time.

4. The water level detection device according to claim 2, characterized in that: The first preset time is the product of 1 / 2 period of the square wave and the filter coefficient.

5. The water level detection device according to claim 4, characterized in that: The 1 / 2 period of the square wave is the 1 / 2 period of the square wave of the maximum frequency, and the filtering coefficient is less than 0.

5.

6. The water level detection device according to claim 1, characterized in that: The acquisition module is a pressure type water level sensor.

7. A water level detection method, characterized in that: include: Collect the oscillation signal corresponding to the current water pressure; The oscillation signal is differentially amplified by a shaping amplifier circuit and the waveform is converted into a square wave; wherein the shaping amplifier circuit includes a differential amplifier, a first resistor, a second resistor, a first capacitor, a second capacitor, a voltage regulator diode and an NPN transistor; wherein, The output end of the differential amplifier is connected to one end of the first resistor, the other end of the first resistor is connected to one end of the first capacitor, the other end of the first capacitor is respectively connected to the cathode of the voltage zener diode and the base of the NPN transistor, the emitter of the NPN transistor is respectively connected to the anode of the voltage zener diode and one end of the second capacitor and is grounded, and the collector of the NPN transistor is respectively connected to one end of the second resistor and the other end of the second capacitor; The voltage regulator diode is also used to control the NPN transistor to output a corresponding square wave according to the waveform output by the differential amplifier; wherein, after the waveform passes through the loop formed by the first resistor, the first capacitor and the voltage regulator diode, when the amplitude of the waveform is greater than 0 and greater than the breakdown voltage of the voltage regulator diode, the amplitude of the waveform is clamped to the breakdown voltage of the voltage regulator diode, and when the breakdown voltage of the voltage regulator diode is greater than the conduction voltage of the base and emitter of the NPN transistor, the NPN transistor is turned on; when the amplitude of the waveform is less than 0 and the value is greater than the conduction voltage of the voltage regulator diode, the base voltage of the NPN transistor is clamped to the negative conduction voltage of the voltage regulator diode, and the NPN transistor is turned off; The frequency of the square wave is detected, and the actual water level is obtained according to the local pre-stored correspondence table between water level and frequency.

8. The water level detection method according to claim 7, characterized in that: The detecting the frequency of the square wave and obtaining the actual water level according to the corresponding relationship table between the water level and the frequency stored locally include: Monitoring the level jump time of the square wave, and filtering out the square wave whose level jump time is less than the first preset time; Counting the square wave filtered by the filter unit within a second preset time to obtain the frequency of the square wave; According to the frequency of the square wave, the local pre-stored correspondence table between water level and frequency is queried to obtain the actual water level.

9. The water level detection method according to claim 8, characterized in that: The first preset time is the product of 1 / 2 period of the square wave and the filter coefficient.

10. A household appliance, characterized in that: It comprises a water level detection device as described in any one of claims 1 to 6.

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