A liquid level detection device

Abstract

This invention discloses a liquid level detection device. The device includes a probe capacitor, a capacitance acquisition circuit, and a controller. The capacitance acquisition circuit is connected to the probe capacitor and generates a capacitance detection signal based on the capacitance value of the probe capacitor. The controller is connected to the capacitance acquisition circuit and determines the current capacitance value of the probe capacitor based on the capacitance detection signal. The controller is further configured to control the liquid level detection output terminal to output a first-level signal when it is determined that the current capacitance value is greater than the upper limit capacitance threshold corresponding to the upper limit of the liquid level, and the duration of the current capacitance value being greater than the upper limit capacitance threshold is greater than or equal to a first preset time; and to control the liquid level detection output terminal to output a second-level signal when it is determined that the current capacitance value is less than the lower limit capacitance threshold corresponding to the lower limit of the liquid level, and the duration of the current capacitance value being less than the lower limit capacitance threshold is greater than or equal to a second preset time. The first preset time is greater than the second preset time. This invention improves the accuracy of oil level detection.

Description

Technical Field

[0001] This invention relates to the field of liquid level detection technology, and more particularly to a liquid level detection device. Background Technology

[0002] Liquid level detection devices are widely used in equipment such as engine oil pans, engine crankcases, electric drive axles, transfer cases, submerged oil-cooled energy storage units, and diesel filters. They are used to detect the liquid level of fluids such as engine oil, coolant, or diesel, and output an alarm signal when the liquid level is too low.

[0003] Existing capacitive level detection devices typically include a capacitive sensing probe. Due to the different dielectric properties of oil and air, the capacitance value of the probe changes accordingly when the oil level changes, allowing the level to be determined based on this change in capacitance. However, in equipment with high-speed rotating gears, such as electric drive bridges and transfer cases, gear rotation may splash oil onto the capacitive sensing probe, causing oil surface fluctuations and resulting in short-term changes in the probe's capacitance value. This affects the stability and accuracy of the level detection results. Summary of the Invention

[0004] This invention provides a liquid level detection device that determines the oil level by combining the current capacitance value of the probe capacitor with the duration for which the current capacitance value meets preset conditions, thereby improving the accuracy of oil level detection.

[0005] The first aspect of the present invention provides a liquid level detection device, which includes: a probe capacitor, a capacitance acquisition circuit, and a controller; The capacitance acquisition circuit is electrically connected to the probe capacitor and is used to generate a capacitance detection signal based on the capacitance value of the probe capacitor. The controller is electrically connected to the capacitance acquisition circuit and is used to acquire the capacitance detection signal in real time and determine the current capacitance value of the probe capacitor based on the capacitance detection signal. The controller is also electrically connected to the liquid level detection output terminal of the liquid level detection device; the controller is also used to control the liquid level detection output terminal to output a first level signal when it is determined that the current capacitance value meets a first preset condition, and to control the liquid level detection output terminal to output a second level signal when it is determined that the current capacitance value meets a second preset condition. The first preset condition includes the current capacitance value being greater than the upper limit capacitance threshold corresponding to the upper limit of the liquid level, and the duration for which the current capacitance value is greater than the upper limit capacitance threshold being greater than or equal to a first preset time; the second preset condition includes the current capacitance value being less than the lower limit capacitance threshold corresponding to the lower limit of the liquid level, and the duration for which the current capacitance value is less than the lower limit capacitance threshold being greater than or equal to a second preset time; the first preset time is greater than the second preset time.

[0006] Optionally, the liquid level detection device may also include: a power module; The power module is used to convert the external power supply voltage into the internal power supply voltage and supply power to the capacitor acquisition circuit and the controller, respectively.

[0007] Optionally, the capacitance acquisition circuit includes a first transistor, a second transistor, a reference capacitor, a first charging resistor, a second charging resistor, a first current-limiting resistor, and a second current-limiting resistor. The emitter of the first transistor is electrically connected to the power module through the first current-limiting resistor, the collector of the first transistor is grounded, and the base of the first transistor is electrically connected to the power module through the second charging resistor. The emitter of the second transistor is electrically connected to the power module through the second current-limiting resistor, the collector of the second transistor is grounded, and the base of the second transistor is electrically connected to the power module through the first charging resistor. The reference capacitor is electrically connected between the emitter of the first transistor and the base of the second transistor, and the probe capacitor is electrically connected between the emitter of the second transistor and the base of the first transistor. The emitter of the second transistor is the capacitance detection signal output terminal of the capacitance acquisition circuit.

[0008] Optionally, the controller is further configured to determine the current capacitance value of the probe capacitor based on a first calculation formula, according to the period of the capacitance detection signal, the resistance value of the first charging resistor, the resistance value of the second charging resistor, and the capacitance value of the reference capacitor. The first calculation formula is: ; in, The period of the capacitance detection signal is denoted as . For preset time coefficient, Let be the resistance value of the first charging resistor. The resistance value of the second charging resistor. The capacitance value of the reference capacitor. This is the current capacitance value of the probe capacitor.

[0009] Optionally, the controller is further configured to, after determining that the current capacitance value meets the first preset condition, if it is detected that the current capacitance value is between the lower limit threshold and the upper limit threshold, control the liquid level detection output terminal to maintain the output of the first level signal; The controller is further configured to, after determining that the current capacitance value meets the second preset condition, if it detects that the current capacitance value is between the lower capacitance threshold and the upper capacitance threshold, control the liquid level detection output terminal to maintain the output of the second level signal.

[0010] Optionally, the liquid level detection device may also include: a probe assembly; The probe assembly includes an inner electrode and an outer electrode that is at least partially disposed around the inner electrode; the inner electrode and the outer electrode are insulated from each other; the probe capacitance and the liquid level detection space are formed between the inner electrode and the outer electrode; The external electrode is provided with a first drainage through hole group and a second drainage through hole group that communicate with the liquid level detection space. The first drainage through hole group and the second drainage through hole group are respectively located on opposite sides of the external electrode. Both the first drainage through hole group and the second drainage through hole group include at least two drainage through holes, and at least two drainage through holes in the same drainage through hole group are arranged sequentially along the axial direction of the external electrode; The drainage hole is an elliptical hole.

[0011] Optionally, the liquid level detection device may also include: a drive circuit; The drive circuit is electrically connected between the controller and the liquid level detection output terminal; The controller is also configured to output a high liquid level drive signal when it is determined that the current capacitance value meets the first preset condition, and to output a low liquid level drive signal when it is determined that the current capacitance value meets the second preset condition; The driving circuit is used to control the liquid level detection output terminal to output the first level signal after receiving the high liquid level driving signal, and to control the liquid level detection output terminal to output the second level signal after receiving the low liquid level driving signal. The power module is also used to supply power to the drive circuit.

[0012] Optionally, the driving circuit includes a first MOSFET, a first resistor, a second resistor, and a third resistor; The gate of the first MOSFET is electrically connected to the drive signal output terminal of the controller through the first resistor, and grounded through the second resistor; The source of the first MOS transistor is grounded, and the drain of the first MOS transistor is electrically connected to the liquid level detection output terminal. The liquid level detection output terminal is also electrically connected to the power module through the third resistor; When the drive signal output terminal outputs the high liquid level drive signal, the first MOS transistor is turned off, and the liquid level detection output terminal outputs a high level; when the drive signal output terminal outputs the low liquid level drive signal, the first MOS transistor is turned on, and the liquid level detection output terminal outputs a low level.

[0013] Optionally, the driving circuit further includes an anti-reverse diode and a transient voltage suppression diode; The anti-reverse diode is electrically connected between the drain of the first MOS transistor and the liquid level detection output terminal; the transient voltage suppression diode is electrically connected between the liquid level detection output terminal and the ground terminal.

[0014] Optionally, the liquid level detection device may also include: an alarm module; The controller is also connected to the alarm module; the controller is also used to control the alarm module to sound an alarm when it is determined that the current capacitance value meets the second preset condition.

[0015] The technical solution of this invention, by setting a probe capacitor, a capacitance acquisition circuit, and a controller in a liquid level detection device, and by electrically connecting the capacitance acquisition circuit to the probe capacitor, enables the capacitance acquisition circuit to generate a capacitance detection signal based on the capacitance value of the probe capacitor. By electrically connecting the controller to both the capacitance acquisition circuit and the liquid level detection output terminal of the liquid level detection device, the controller can acquire the capacitance detection signal in real time and determine the current capacitance value of the probe capacitor based on the capacitance detection signal. Therefore, when the current capacitance value is determined to be greater than the upper limit threshold corresponding to the upper limit threshold of the liquid level, and the duration of the current capacitance value being greater than the upper limit threshold is greater than or equal to a first preset time, the controller outputs a first-level signal at the liquid level detection output terminal. Conversely, when the current capacitance value is determined to be less than the lower limit threshold corresponding to the lower limit threshold of the liquid level, and the duration of the current capacitance value being less than the lower limit threshold is greater than or equal to a second preset time, the controller outputs a second-level signal at the liquid level detection output terminal. By setting the first preset time to be greater than the second preset time, a delay filtering of the capacitance detection result is achieved, which can reduce liquid level misjudgments caused by oil splashing and liquid surface fluctuations, and improve the stability and accuracy of liquid level detection.

[0016] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a liquid level detection device provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of another liquid level detection device provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of a capacitance acquisition circuit provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a driving circuit provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of another liquid level detection device provided in an embodiment of the present invention; Figure 6 This is an exploded view of a liquid level detection device provided in an embodiment of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] Figure 1 This is a schematic diagram of the structure of a liquid level detection device provided in an embodiment of the present invention. Figure 1As shown, the liquid level detection device includes: a probe capacitor 1, a capacitance acquisition circuit 2, and a controller 3; the capacitance acquisition circuit 2 is electrically connected to the probe capacitor 1 and is used to generate a capacitance detection signal based on the capacitance value of the probe capacitor 1; the controller 3 is electrically connected to the capacitance acquisition circuit 2 and is used to acquire the capacitance detection signal in real time and determine the current capacitance value of the probe capacitor 1 based on the capacitance detection signal; the controller 3 is also electrically connected to the liquid level detection output terminal 01 of the liquid level detection device; the controller 3 is also used to control the liquid level detection output terminal 01 to output a first level signal when it is determined that the current capacitance value meets a first preset condition, and to control the liquid level detection output terminal 01 to output a second level signal when it is determined that the current capacitance value meets a second preset condition; wherein, the first preset condition includes the current capacitance value being greater than the upper limit threshold corresponding to the upper limit threshold of the liquid level, and the duration for which the current capacitance value is greater than the upper limit threshold of the liquid level is greater than or equal to a first preset time; the second preset condition includes the current capacitance value being less than the lower limit threshold corresponding to the lower limit threshold of the liquid level, and the duration for which the current capacitance value is less than the lower limit threshold of the liquid level is greater than or equal to a second preset time; the first preset time is greater than the second preset time.

[0022] Specifically, probe capacitor 1 is used to sense changes in the level of the oil being tested. When the level of the oil changes, the degree to which probe capacitor 1 is in contact with or submerged in the oil changes accordingly. Because the dielectric properties of the oil and air are different, the capacitance of probe capacitor 1 also changes. When the level of the oil rises, the contact area between probe capacitor 1 and the oil increases, and the capacitance of probe capacitor 1 increases accordingly; when the level of the oil decreases, the contact area between probe capacitor 1 and the oil decreases, and the capacitance of probe capacitor 1 decreases accordingly. Therefore, the capacitance of probe capacitor 1 is positively correlated with the level of the oil, and the capacitance value of probe capacitor 1 can be used to characterize the level state of the oil.

[0023] The capacitance acquisition circuit 2 is used to convert the capacitance value of the probe capacitor 1 into a capacitance detection signal that is easy for the controller 3 to acquire and process. For example, the capacitance acquisition circuit 2 may include an oscillation circuit, and the probe capacitor 1 can serve as a timing capacitor in the oscillation circuit. When the capacitance value of the probe capacitor 1 changes, the charging time, discharging time, or oscillation period of the oscillation circuit changes accordingly, thereby causing a change in the capacitance detection signal output by the capacitance acquisition circuit 2. The capacitance detection signal can be a periodic pulse signal, such as a pulse width modulation (PWM) signal, a square wave signal, or other signals that can characterize the capacitance value of the probe capacitor 1 through its period, frequency, pulse width, or duty cycle. When the capacitance detection signal is a PWM signal, a change in the capacitance value of the probe capacitor 1 can cause a change in the frequency, period, or pulse width of the PWM signal; when the capacitance detection signal is a square wave signal, a change in the capacitance value of the probe capacitor 1 can cause a change in the period, high-level duration, or low-level duration of the square wave signal.

[0024] Controller 3 can be a microcontroller unit (MCU). Controller 3 can acquire capacitance detection signals according to a preset sampling period and obtain at least one of the following signal parameters: frequency, period, high-level duration, low-level duration, and duty cycle. Controller 3 can determine the current capacitance value of probe capacitor 1 based on a pre-established correspondence between signal parameters and capacitance values, or based on a preset calculation formula. The method by which controller 3 determines the current capacitance value of probe capacitor 1 based on the capacitance detection signal can be determined according to actual needs, and this invention does not impose specific limitations on this.

[0025] The controller 3 can preset the upper limit threshold of the capacitance corresponding to the upper limit threshold of the liquid level and the lower limit threshold of the capacitance corresponding to the lower limit threshold of the liquid level. The upper limit threshold of the liquid level is used to characterize the liquid level height corresponding to the normal or high liquid level state of the oil being tested, and the upper limit threshold of the capacitance is the capacitance judgment value of probe capacitor 1 at that liquid level height. The lower limit threshold of the liquid level is used to characterize the liquid level height corresponding to the low or alarm liquid level state of the oil being tested, and the lower limit threshold of the capacitance is the capacitance judgment value of probe capacitor 1 at that liquid level height. After determining the current capacitance value of probe capacitor 1, the controller 3 can further compare the current capacitance value with the upper limit threshold and the lower limit threshold of the capacitance. If the current capacitance value is greater than the upper limit threshold of the capacitance, it indicates that the probe capacitor 1 is in high contact with the oil being tested, and the liquid level of the oil being tested may be higher than the upper limit threshold of the liquid level; if the current capacitance value is less than the lower limit threshold of the capacitance, it indicates that the probe capacitor 1 is in low contact with the oil being tested, and the liquid level of the oil being tested may be lower than the lower limit threshold of the liquid level.

[0026] Furthermore, the controller 3 can also determine the duration for which the current capacitance value meets the corresponding threshold condition. It is understood that if the current capacitance value is greater than the upper limit threshold, and the current capacitance value remains greater than the upper limit threshold for a period greater than or equal to a first preset time, it indicates that the probe capacitor 1 continuously exhibits capacitance characteristics corresponding to a high liquid level for a relatively long period. In this case, the controller 3 will determine that the oil to be tested is in a high liquid level state and control the liquid level detection output terminal 01 to output a first level signal. If the current capacitance value is less than the lower limit threshold, and the current capacitance value remains less than the lower limit threshold for a period greater than or equal to a second preset time, it indicates that the probe capacitor 1 continuously exhibits capacitance characteristics corresponding to a low liquid level for a relatively long period. In this case, the controller 3 will determine that the oil to be tested is in a low liquid level state and control the liquid level detection output terminal 01 to output a second level signal. For example, the first level signal can be a high-level signal with a voltage range of 3.4V-5V, and the second level signal can be a low-level signal with a voltage range of 0V-0.5V. This invention does not specifically limit these values. The liquid level detection output terminal 01 can be connected to an external controller so that the external controller can perform liquid level display or protection control based on the level signal output by the liquid level detection output terminal 01.

[0027] It is also understandable that the oil splashing caused by the high-speed rotation of the gears usually causes the capacitance value of probe capacitor 1 to increase in a short period of time. If the current capacitance value is immediately determined to be high when it just exceeds the upper limit threshold, the instantaneous capacitance change caused by oil splashing may be misjudged as a true high liquid level. Therefore, by setting the system to confirm that the oil under test is in a high liquid level state only after the current capacitance value has been continuously greater than the upper limit threshold for a first preset time, the short-term increase in capacitance value caused by oil splashing can be filtered out. When the current capacitance value is continuously less than the lower limit threshold, it indicates that probe capacitor 1 has detached from the oil under test, and the oil under test may be in a state of insufficient oil or low liquid level. In order to output a low liquid level alarm signal in a timely manner, the first preset time can be set to be greater than the second preset time. Thus, the liquid level detection device can quickly identify the true low liquid level state while preventing the misjudgment of high liquid level caused by oil splashing. For example, controller 3 can acquire a capacitance detection signal every 8ms. When the current capacitance value acquired 1250 times is greater than the upper limit threshold, and the current capacitance value remains greater than the upper limit threshold for 10s, controller 3 determines that the current capacitance value meets the first preset condition and controls the liquid level detection output terminal 01 to output a high-level signal. When the current capacitance value acquired 100 times is less than the lower limit threshold, and the current capacitance value remains less than the lower limit threshold for 0.8s, controller 3 determines that the current capacitance value meets the second preset condition and controls the liquid level detection output terminal 01 to output a low-level signal.

[0028] The liquid level of the oil under test is determined by combining the current capacitance value of probe capacitor 1 and the time during which the current capacitance value continuously meets the corresponding threshold condition. This achieves delayed filtering of the capacitance detection results, thereby reducing misjudgment of liquid level caused by oil splashing and surface fluctuations, and improving the stability and accuracy of liquid level detection.

[0029] In this embodiment, a probe capacitor 1, a capacitance acquisition circuit 2, and a controller 3 are incorporated into the liquid level detection device. The capacitance acquisition circuit 2 is electrically connected to the probe capacitor 1, enabling it to generate a capacitance detection signal based on the capacitance value of the probe capacitor 1. The controller 3 is electrically connected to both the capacitance acquisition circuit 2 and the liquid level detection output terminal 01 of the liquid level detection device. This allows the controller 3 to acquire the capacitance detection signal in real time and determine the current capacitance value of the probe capacitor 1 based on the signal. When the current capacitance value is determined to be greater than the upper limit threshold corresponding to the upper limit of the liquid level, and the duration of this value being greater than or equal to a first preset time, the controller 01 outputs a first-level signal. Conversely, when the current capacitance value is determined to be less than the lower limit threshold corresponding to the lower limit of the liquid level, and the duration of this value being less than or equal to a second preset time, the controller 01 outputs a second-level signal. By setting the first preset time to be greater than the second preset time, a delay filtering effect on the capacitance detection results is achieved. This reduces misjudgments of the liquid level caused by oil splashing and surface fluctuations, improving the stability and accuracy of the liquid level detection.

[0030] Optional, Figure 2 This is a schematic diagram of another liquid level detection device provided in an embodiment of the present invention. Figure 2 As shown, the liquid level detection device also includes a power supply module 4; the power supply module 4 is used to convert the external power supply voltage into the internal power supply voltage and supply power to the capacitor acquisition circuit 2 and the controller 3 respectively.

[0031] Specifically, the power supply module 4 receives an external power supply voltage and converts it into an internal power supply voltage suitable for the operation of the capacitor acquisition circuit 2 and the controller 3, thereby enabling the internal power supply voltage to be provided to the capacitor acquisition circuit 2 and the controller 3 respectively. For example, the external power supply voltage can be 5V, and the power supply module 4 may include at least one of a step-down unit, a voltage regulator unit, and a filter unit. The step-down unit reduces the external power supply voltage to the operating voltage required by the capacitor acquisition circuit 2 and the controller 3; the voltage regulator unit reduces the impact of external power supply voltage fluctuations on the internal power supply voltage; and the filter unit filters out pulse interference or high-frequency noise in the external power supply voltage to improve the stability of the internal power supply voltage. This improves the stability of the capacitance detection signal output by the capacitor acquisition circuit 2 and the accuracy of the liquid level detection results.

[0032] Optional, Figure 3 This is a schematic diagram of a capacitance acquisition circuit provided in an embodiment of the present invention. Figure 3 As shown, the capacitance acquisition circuit 2 includes a first transistor Q1, a second transistor Q2, a reference capacitor C1, a first charging resistor R1, a second charging resistor R2, a first current-limiting resistor R3, and a second current-limiting resistor R4. The emitter of the first transistor Q1 is electrically connected to the power module 4 through the first current-limiting resistor R3, the collector of the first transistor Q1 is grounded, and the base of the first transistor Q1 is electrically connected to the power module 4 through the second charging resistor R2. The emitter of the second transistor Q2 is electrically connected to the power module 4 through the second current-limiting resistor R4, the collector of the second transistor Q2 is grounded, and the base of the second transistor Q2 is electrically connected to the power module 4 through the first charging resistor R1. The reference capacitor C1 is electrically connected between the emitter of the first transistor Q1 and the base of the second transistor Q2, and the probe capacitor 1 is electrically connected between the emitter of the second transistor Q2 and the base of the first transistor Q1. The emitter of the second transistor Q2 is the capacitance detection signal output terminal O2 of the capacitance acquisition circuit 2.

[0033] Specifically, the first transistor Q1 and the second transistor Q2 can be transistors of the same specification to ensure that the circuits on both sides have similar conduction and cutoff characteristics. The reference capacitor C1 is a capacitor with a known capacitance value. The first transistor Q1 and the second transistor Q2 form a cross-coupled circuit through the reference capacitor C1 and the probe capacitor 1. The emitter of the second transistor Q2 is the capacitance detection signal output terminal O2 of the capacitance acquisition circuit 2. The second current-limiting resistor R4 not only limits the current flowing through the second transistor Q2, but also pulls up the capacitance detection signal output terminal O2 to the internal supply voltage when the second transistor Q2 is off. Thus, when the second transistor Q2 is off, the capacitance detection signal output terminal O2 outputs a high level; when the second transistor Q2 is on, the potential of the capacitance detection signal output terminal O2 is pulled low, and a low level is output.

[0034] After the capacitance acquisition circuit 2 is powered on, due to the difficulty in achieving perfect consistency in the component parameters, resistance values, and capacitance values ​​of the two circuits, one of the first transistor Q1 and the second transistor Q2 will initially turn on while the other turns off. Assuming the first transistor Q1 turns on first and the second transistor Q2 turns off, the potential change at the emitter of the first transistor Q1 is coupled to the base of the second transistor Q2 through the reference capacitor C1, keeping the second transistor Q2 off. At this time, the power module 4 charges the reference capacitor C1 through the first charging resistor R1, causing the base potential of the second transistor Q2 to gradually change.

[0035] When the base potential of the second transistor Q2 reaches the corresponding state switching threshold, the second transistor Q2 begins to conduct. The potential change at the emitter of the second transistor Q2 is coupled to the base of the first transistor Q1 through the probe capacitor 1, causing the first transistor Q1 to switch from the conducting state to the cutoff state. Under the effect of cross-coupling, the second transistor Q2 further conducts, and the first transistor Q1 further cuts off, thus enabling the circuit to quickly complete the state transition. At this time, the capacitance detection signal output terminal O2 switches from a high level to a low level.

[0036] After the second transistor Q2 is turned on and the first transistor Q1 is turned off, the power module 4 charges the probe capacitor 1 through the second charging resistor R2, causing the base potential of the first transistor Q1 to gradually change. When the base potential of the first transistor Q1 reaches the corresponding state switching threshold, the first transistor Q1 is turned on again, and the second transistor Q2 is turned off through the reference capacitor C1, thus causing the circuit to flip again. At this time, the capacitance detection signal output terminal O2 switches from low level to high level.

[0037] Therefore, the first transistor Q1 and the second transistor Q2 alternately turn on and off under the action of the reference capacitor C1, the probe capacitor 1, the first charging resistor R1, and the second charging resistor R2, causing the capacitance detection signal output terminal O2 to periodically switch between high and low levels and output a periodic square wave signal. The reference capacitor C1 and the first charging resistor R1 determine the duration of one state, while the probe capacitor 1 and the second charging resistor R2 determine the duration of the other state. Therefore, when the capacitance value of the probe capacitor 1 changes, the period of the capacitance detection signal will also change accordingly.

[0038] Optionally, the controller 3 is further configured to determine the current capacitance value of the probe capacitor 1 based on a first calculation formula, according to the period of the capacitance detection signal, the resistance value of the first charging resistor R1, the resistance value of the second charging resistor R2, and the capacitance value of the reference capacitor C1; wherein the first calculation formula is: ;in, The period of the capacitance detection signal. For preset time coefficient, Let R1 be the resistance value of the first charging resistor. The resistance value of the second charging resistor R2. The capacitance value of the reference capacitor C1, This is the current capacitance value of probe capacitor 1.

[0039] Specifically, the duration of the charging phase corresponding to the reference capacitor C1 is recorded as the first duration. Then the first duration It can be represented as: For example, a preset time coefficient It can be 0.693. The duration of the charging phase corresponding to probe capacitor 1 is recorded as the second duration. Then the second duration It can be represented as: A complete cycle of the capacitance detection signal. Including the first duration Second duration ,therefore: This allows us to further analyze and obtain the current capacitance value of probe capacitor 1. for .

[0040] The controller 3 can acquire the square wave signal output from the capacitance detection signal output terminal 02 and determine the time interval between two adjacent identical edges of the square wave signal to obtain the period of the capacitance detection signal. Since the resistance values ​​of the first charging resistor R1, the second charging resistor R2, and the reference capacitor C1 are all known parameters, the controller 3 can calculate the current capacitance value of the probe capacitor 1 according to the first calculation formula. The capacitance acquisition circuit 2 can convert the change in the capacitance value of the probe capacitor 1 into a periodic change of the square wave signal, which helps to reduce the difficulty of capacitance detection and improve the stability of capacitance value acquisition.

[0041] Optionally, the controller 3 is further configured to, after determining that the current capacitance value meets the first preset condition, if the current capacitance value is detected to be between the lower limit threshold and the upper limit threshold, control the liquid level detection output terminal 01 to maintain the output of the first level signal; the controller 3 is further configured to, after determining that the current capacitance value meets the second preset condition, if the current capacitance value is detected to be between the lower limit threshold and the upper limit threshold, control the liquid level detection output terminal 01 to maintain the output of the second level signal.

[0042] It should be noted that after the power module 4 powers on the controller 3, the controller 3 can first perform an initialization operation. During the initialization process, the liquid level detection output terminal 01 outputs a first-level signal by default to avoid false alarms when the oil being tested is at a high liquid level. The initialization time can be, for example, 1.5 seconds. After initialization is completed, the controller 3 begins to collect the current capacitance value of the probe capacitor 1 and determines the liquid level based on the current capacitance value.

[0043] Specifically, a hysteresis interval for liquid level determination is formed between the upper and lower capacitance thresholds. The upper capacitance threshold corresponds to the upper liquid level threshold, and the lower capacitance threshold corresponds to the lower liquid level threshold. When controller 3 detects that the current capacitance value is between the lower and upper capacitance thresholds, it does not switch the level signal output by liquid level detection output terminal 01 according to the current capacitance value, but maintains the level signal output by liquid level detection output terminal 01 that was determined before entering this interval.

[0044] In an exemplary embodiment, when the controller 3 has determined that the current capacitance value meets the first preset condition and controls the liquid level detection output terminal 01 to output a first level signal, it indicates that the oil under test is in a high liquid level state. Subsequently, if the liquid level of the oil under test gradually decreases from above the upper limit threshold to between the lower limit threshold and the upper limit threshold, causing the current capacitance value to be between the lower limit threshold and the upper limit threshold, the controller 3 maintains the high liquid level determination and controls the liquid level detection output terminal 01 to continue outputting the first level signal. Only when the current capacitance value further decreases to below the lower limit threshold and the duration reaches the second preset time, does the controller 3 determine that the current capacitance value meets the second preset condition and control the liquid level detection output terminal 01 to output a second level signal.

[0045] In another exemplary embodiment, when the controller 3 has determined that the current capacitance value meets the second preset condition and controls the liquid level detection output terminal 01 to output a second level signal, it indicates that the oil under test is in a low liquid level state. Subsequently, if the liquid level of the oil under test gradually rises from below the lower liquid level threshold to between the lower and upper liquid level thresholds, causing the current capacitance value to be between the lower and upper capacitance thresholds, the controller 3 maintains the low liquid level determination and controls the liquid level detection output terminal 01 to continue outputting the second level signal. Only when the current capacitance value further rises to above the upper capacitance threshold, and the duration reaches the first preset time, does the controller 3 determine that the current capacitance value meets the first preset condition and control the liquid level detection output terminal 01 to output a first level signal.

[0046] It is understandable that by setting an upper and lower threshold for the capacitor and a hysteresis interval between them, the level signal output by the level detection output terminal 01 can be prevented from frequently switching between the first and second level signals when the level of the oil being tested fluctuates near the threshold, thereby improving the stability and accuracy of the level determination result.

[0047] Optional, continue to refer to Figure 2 The liquid level detection device further includes: a drive circuit 5; the drive circuit 5 is electrically connected between the controller 3 and the liquid level detection output terminal 01; the controller 3 is also used to output a high liquid level drive signal when it is determined that the current capacitance value meets the first preset condition, and to output a low liquid level drive signal when it is determined that the current capacitance value meets the second preset condition; the drive circuit 5 is used to control the liquid level detection output terminal 01 to output a first level signal after receiving the high liquid level drive signal, and to control the liquid level detection output terminal 01 to output a second level signal after receiving the low liquid level drive signal; the power supply module 4 is also used to supply power to the drive circuit 5.

[0048] Specifically, when controller 3 determines that the current capacitance value meets the first preset condition, it indicates that the oil under test is in a high-level state. Controller 3 can output a high-level drive signal to drive circuit 5 through drive signal output terminal 03, so that drive circuit 5 can control level detection output terminal 01 to output a first-level signal according to the high-level drive signal. When controller 3 determines that the current capacitance value meets the second preset condition, it indicates that the oil under test is in a low-level state. Controller 3 can output a low-level drive signal to drive circuit 5 through drive signal output terminal 03, so that drive circuit 5 can control level detection output terminal 01 to output a second-level signal according to the low-level drive signal.

[0049] The liquid level detection output terminal 01 can be connected to the signal input terminal of an external controller, enabling the external controller to identify the liquid level status of the oil under test based on the level signal output by the liquid level detection output terminal 01. The liquid level detection output terminal 01 can also be connected to the power supply module 4 via a pull-up load such as a relay, indicator light, buzzer, or resistor. When the drive circuit 5 is not connected to the ground terminal, the liquid level detection output terminal 01 presents a high level under the action of the power supply module 4 and the pull-up load; when the drive circuit 5 is connected to the ground terminal, the liquid level detection output terminal 01 is pulled low to near the ground potential, thus presenting a low level.

[0050] Optional, Figure 4 This is a schematic diagram of a driving circuit provided in an embodiment of the present invention. Figure 4 As shown, the driving circuit 5 includes a first MOSFET Q3, a first resistor R5, a second resistor R6, and a third resistor R7. The gate of the first MOSFET Q3 is electrically connected to the driving signal output terminal 03 of the controller 3 through the first resistor R5, and grounded through the second resistor R6. The source of the first MOSFET Q3 is grounded, and the drain of the first MOSFET Q3 is electrically connected to the liquid level detection output terminal 01. The liquid level detection output terminal 01 is also electrically connected to the power module 4 through the third resistor R7. When the driving signal output terminal 03 outputs a high liquid level driving signal, the first MOSFET Q3 is turned off, and the liquid level detection output terminal 01 outputs a high level. When the driving signal output terminal 03 outputs a low liquid level driving signal, the first MOSFET Q3 is turned on, and the liquid level detection output terminal 01 outputs a low level.

[0051] Specifically, the first MOSFET Q3 can be an N-channel MOSFET. The first resistor R5 is a gate series resistor, used to limit the instantaneous current at the gate of the first MOSFET Q3 during charging and discharging, reducing the impact of the switching process of the first MOSFET Q3 on the drive signal output terminal 03 of the controller 3, and suppressing signal oscillation during the switching process. The second resistor R6 is a gate pull-down resistor, used to maintain the gate of the first MOSFET Q3 at a low level when the controller 3 has not yet output a valid drive signal or when the drive signal output terminal 03 is in a high-impedance state, ensuring reliable turn-off of the first MOSFET Q3 and preventing false turn-on due to a floating gate. The third resistor R7 is a pull-up resistor, used to pull the liquid level detection output terminal 01 to the internal power supply voltage to form a high-level signal when the first MOSFET Q3 is off; the third resistor R7 also limits the current flowing from the power module 4 to the ground terminal when the first MOSFET Q3 is on.

[0052] For example, the high liquid level drive signal can be a low-level signal. When the controller 3 determines that the current capacitance value meets the first preset condition, the drive signal output terminal 03 outputs a low level, causing the gate-source voltage of the first MOSFET Q3 to fall below the conduction threshold, and the first MOSFET Q3 is turned off. At this time, the conductive path between the liquid level detection output terminal 01 and the ground terminal is broken, and the liquid level detection output terminal 01 is pulled up to the internal power supply voltage through the third resistor R7, thereby outputting a high level, indicating that the oil under test is in a high liquid level state. The low liquid level drive signal can be a high-level signal. When the controller 3 determines that the current capacitance value meets the second preset condition, the drive signal output terminal 03 outputs a high level, causing the gate-source voltage of the first MOSFET Q3 to reach the conduction threshold, and the first MOSFET Q3 is turned on. At this time, the liquid level detection output terminal 01 forms a conductive path with the ground terminal through the first MOSFET Q3, and the liquid level detection output terminal 01 is pulled down to near the ground potential, thereby outputting a low level, indicating that the oil under test is in a low liquid level state.

[0053] Therefore, the first MOSFET Q3 forms a low-side switching structure. The controller 3 only needs to control the conduction and cutoff of the first MOSFET Q3 to switch the liquid level detection output terminal 01 between high and low levels. By converting the drive signal output by the controller 3 through the drive circuit 5, the external load can be avoided from being directly driven by the drive signal output terminal 03 of the controller 3, thereby improving the output drive capability and interface reliability of the liquid level detection device.

[0054] Optional, continue to refer to Figure 4 The driving circuit 5 also includes a reverse protection diode D1 and a transient voltage suppression diode D2; the reverse protection diode D1 is electrically connected between the drain of the first MOSFET Q3 and the liquid level detection output terminal 01; the transient voltage suppression diode D2 is electrically connected between the liquid level detection output terminal 01 and the ground terminal.

[0055] Specifically, the reverse protection diode D1 is connected in series between the drain of the first MOSFET Q3 and the liquid level detection output terminal O1, so that the normal pull-down current of the liquid level detection output terminal O1 can flow to the ground terminal through the reverse protection diode D1 and the first MOSFET Q3. At the same time, the reverse protection diode D1 can also block the reverse current when the power module 4 or the pull-up load is reverse connected, reducing the probability of reverse current entering the first MOSFET Q3 and the internal circuit of the liquid level detection device.

[0056] Transient voltage suppression diode D2 is electrically connected between the liquid level detection output terminal 01 and the ground terminal. When the voltage of the liquid level detection output terminal 01 is within the normal operating range, the transient voltage suppression diode D2 is in the off state and does not affect the normal level output of the liquid level detection output terminal 01. When the liquid level detection output terminal 01 is subjected to transient high voltage impacts caused by electrostatic discharge, surge voltage, or external inductive load, the transient voltage suppression diode D2 conducts, dissipates the transient current to the ground terminal, and limits the voltage of the liquid level detection output terminal 01, thereby reducing the risk of damage to the first MOSFET Q3 and controller 3 by transient high voltage.

[0057] By setting up anti-reverse diode D1 and transient voltage suppression diode D2, the tolerance of the liquid level detection output terminal 01 to reverse wiring, electrostatic discharge and surge impact can be improved, thereby improving the output stability and reliability of the liquid level detection device.

[0058] Optional, continue to refer to Figure 2 The liquid level detection device also includes: an alarm module 6; a controller 3 is also connected to the alarm module 6; the controller 3 is also used to control the alarm module 6 to sound an alarm when it is determined that the current capacitance value meets the second preset condition.

[0059] Understandably, when controller 3 determines that the current capacitance value of probe capacitor 1 meets the second preset condition, it indicates that the oil to be tested is in a low-level state. At this time, controller 3 can further control alarm module 6 to output low-level alarm information to remind relevant personnel to replenish the oil to be tested in time or to take protective measures such as shutdown or power reduction for the corresponding equipment. For example, alarm module 6 may include at least one of a sound alarm unit, a light alarm unit, and a communication alarm unit. The sound alarm unit may include a buzzer or speaker to provide sound alarm through beeping, voice prompts, etc.; the light alarm unit may include an indicator light or display screen to provide light alarm by illuminating, flashing, or displaying alarm information; the communication alarm unit can communicate with an external controller, monitoring platform, or user terminal to send low-level alarm information to the external controller, remote monitoring platform, mobile terminal, or other receiving device to achieve remote alarm. Thus, when the level of the oil to be tested is lower than the lower limit threshold, relevant personnel can be promptly reminded, reducing the risk of wear or damage to the equipment due to continued operation in a low-oil state.

[0060] Optional, Figure 5 This is a schematic diagram of another liquid level detection device provided in an embodiment of the present invention. Figure 6 This is an exploded view of a liquid level detection device provided in an embodiment of the present invention. (Combined with...) Figure 5 and Figure 6 As shown, the liquid level detection device further includes: a probe assembly 10; the probe assembly 10 includes an inner electrode 11 and an outer electrode 12 at least partially surrounding the inner electrode 11; the inner electrode 11 and the outer electrode 12 are insulated from each other; a probe capacitor 1 and a liquid level detection space are formed between the inner electrode 11 and the outer electrode 12; the outer electrode 12 is provided with a first drainage through hole group and a second drainage through hole group communicating with the liquid level detection space, the first drainage through hole group and the second drainage through hole group are respectively provided on opposite sides of the outer electrode 12; the first drainage through hole group and the second drainage through hole group each include at least two drainage through holes 13, and at least two drainage through holes 13 in the same drainage through hole group are arranged sequentially along the axial direction of the outer electrode 12; the drainage through holes 13 are elliptical through holes.

[0061] Specifically, the liquid level detection device may include a connector 14, a connecting terminal 15, a sealing ring 16, a printed circuit board 17, a hexagonal body 18, a mounting sealing ring 19, a connecting piece 20, and a probe assembly 10. The connector 14, printed circuit board 17, and hexagonal body 18 constitute the signal connection and processing part of the liquid level detection device. The probe assembly 10 is located on the side of the hexagonal body 18 away from the connector 14 and is used to extend into the container or equipment containing the liquid to be tested to detect the liquid level. Position H2 on the probe assembly 10 can correspond to the lower liquid level threshold, and position H1 on the probe assembly 10 can correspond to the upper liquid level threshold.

[0062] Connector 14 is used to connect to an external controller or external wiring harness to receive external power supply voltage and output a liquid level detection signal to the external controller. For example, connector 14 may be made of a blend of polybutylene terephthalate and acrylonitrile-styrene-acrylate copolymer, and may contain glass fiber to improve the mechanical strength and heat resistance of connector 14. Connector 14 may be manufactured using injection molding. Connection terminal 15 is disposed within connector 14 and electrically connected to printed circuit board 17 for transmitting power supply signals, grounding signals, and liquid level detection signals between the external controller and the printed circuit board 17 assembly. For example, connection terminal 15 may be made of brass and may have a tin-plated layer on its surface to improve the conductivity, corrosion resistance, and solderability of connection terminal 15. Connection terminal 15 may be formed by machining and bending processes. A sealing ring 16 is disposed between connector 14 and hexagonal body 18 to seal the assembly gap between connector 14 and hexagonal body 18 to prevent moisture, dust, or oil from entering the liquid level detection device. For example, the sealing ring 16 can be made of fluororubber and can be formed by a vulcanization molding process.

[0063] A printed circuit board 17 is disposed within the receiving space formed by the connector 14 and the hexagonal body 18, used to collect and process the liquid level detection information output by the probe assembly 10, and generate corresponding liquid level status signals. The capacitor acquisition circuit 2, controller 3, power module 4, and drive circuit 5 can be integrated onto the printed circuit board 17. The hexagonal body 18 is disposed between the connector 14 and the probe assembly 10, used to house and protect the printed circuit board 17, and also used to install the liquid level detection device onto an oil tank, housing, or other equipment under test. A hexagonal wrench mating surface can be provided on the outer periphery of the hexagonal body 18 to facilitate the installation or removal of the liquid level detection device using a wrench; a mounting thread can be provided at the end of the hexagonal body 18 near the probe assembly 10 for threaded connection with the mounting hole on the equipment under test. For example, the hexagonal body 18 can be made of stainless steel and can be formed by CNC machining. The hexagonal body 18 can also have a corresponding pressure-bearing capacity, for example, a maximum withstand pressure of 1.4 bar. The mounting seal 19 is disposed between the hexagonal body 18 and the mounting surface of the device under test. When the hexagonal body 18 is installed to the device under test via mounting threads, the mounting seal 19 is pressed between the hexagonal body 18 and the mounting surface to prevent the tested oil from leaking outward from the mounting threads. For example, the mounting seal can be made of fluororubber.

[0064] A connecting piece 20 is disposed between the printed circuit board 17 and the probe assembly 10, and is electrically connected to both the printed circuit board 17 and the inner electrode 11. The connecting piece is used to fix the inner electrode 11, maintaining it in a preset position relative to the outer electrode 12, and to transmit the electrical signal collected by the inner electrode 11 to the printed circuit board 17. The connecting piece 20 may have a symmetrical structure to support the inner electrode 11 from opposite sides, reducing the probability of the inner electrode 11 shifting under vibration. For example, the connecting piece 20 may be made of phosphor bronze, and a tin-plated layer may be provided on its surface to improve conductivity and solderability.

[0065] The probe assembly 10 includes an inner electrode 11 and an outer electrode 12 at least partially surrounding the inner electrode 11. The inner electrode 11 and the outer electrode 12 are insulated from each other, forming a liquid level detection space between them. The inner electrode 11 and the outer electrode 12 together form the probe capacitor 1. For example, the inner electrode 11 may include a copper sleeve, and an insulating sleeve 21 may be fitted over the outer side of the inner electrode 11, located between the inner electrode 11 and the outer electrode 12 to provide an insulating gap between them. For example, the insulating sleeve 21 may be a polytetrafluoroethylene (PTFE) sleeve. PTFE sleeves have good electrical insulation, oil resistance, and corrosion resistance, which can maintain the distance between the inner electrode 11 and the outer electrode 12 while reducing the impact of the oil being tested on the internal copper sleeve and the internal structure of the liquid level detection device. Multiple O-rings 22 may be provided between the inner electrode 11 and the insulating sleeve 21. These O-rings 22 seal the assembly gap between the inner electrode 11 and the insulating sleeve 21, preventing the tested oil from entering the receiving space of the printed circuit board 17 through the gap between the inner electrode 11 and the insulating sleeve 21. For example, the O-rings 22 may be made of fluororubber. The outer electrode 12 may include a stainless steel outer sleeve that at least partially surrounds the insulating sleeve 21. The stainless steel outer sleeve serves as the outer electrode of the probe capacitor 1 and protects the insulating sleeve and inner electrode 11 disposed within it.

[0066] When the oil to be tested enters or leaves the liquid level detection space, the dielectric environment between the inner electrode 11 and the outer electrode 12 changes, causing the capacitance value of the probe capacitor 1 to change with the liquid level of the oil to be tested. The outer electrode 12 is provided with a first drainage through-hole group and a second drainage through-hole group communicating with the liquid level detection space. The first and second drainage through-hole groups are respectively located on opposite sides of the outer electrode 12. Both the first and second drainage through-hole groups include at least two drainage through-holes 13, and the at least two drainage through-holes 13 in the same drainage through-hole group are arranged sequentially along the axial direction of the outer electrode 12. For example, two drainage through-holes 13 can be provided on the front and back sides of the outer electrode 12 respectively, and the drainage through-holes 13 can be elliptical through-holes.

[0067] Each drain hole 13 is connected to the liquid level detection space, so that the oil to be tested can enter or leave the liquid level detection space through the drain hole 13. By setting drain hole groups on opposite sides of the outer electrode 12 and arranging multiple drain holes 13 in the same drain hole group along the axial direction of the outer electrode 12, the communication area between the liquid level detection space and the external space can be increased, and oil flow paths can be formed at different axial positions and different circumferential sides of the outer electrode 12.

[0068] When the oil generated by the high-speed rotation of the gear splashes onto the probe assembly 10, the oil entering the liquid level detection space can quickly flow out from the opposite sides of the outer electrode 12 through the first and second drainage through-hole groups. The elliptical through-holes can form a larger drainage opening, further improving the oil outflow efficiency, thereby reducing the probability of oil deposition, adhesion, or the formation of a continuous oil film between the inner electrode 11 and the outer electrode 12, and shortening the residence time of the splashed oil in the liquid level detection space. This reduces the risk of a short-term increase in the capacitance value of the probe capacitor 1 due to splashed oil, and the misjudgment of a low liquid level as a high liquid level, thus improving the stability and accuracy of liquid level detection.

[0069] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0070] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A liquid level detection device, characterized in that, include: Probe capacitor, capacitance acquisition circuit, and controller; The capacitance acquisition circuit is electrically connected to the probe capacitor and is used to generate a capacitance detection signal based on the capacitance value of the probe capacitor. The controller is electrically connected to the capacitance acquisition circuit and is used to acquire the capacitance detection signal in real time and determine the current capacitance value of the probe capacitor based on the capacitance detection signal. The controller is also electrically connected to the liquid level detection output terminal of the liquid level detection device; the controller is also used to control the liquid level detection output terminal to output a first level signal when it is determined that the current capacitance value meets a first preset condition, and to control the liquid level detection output terminal to output a second level signal when it is determined that the current capacitance value meets a second preset condition. The first preset condition includes the current capacitance value being greater than the upper limit capacitance threshold corresponding to the upper limit of the liquid level, and the duration for which the current capacitance value is greater than the upper limit capacitance threshold being greater than or equal to a first preset time; the second preset condition includes the current capacitance value being less than the lower limit capacitance threshold corresponding to the lower limit of the liquid level, and the duration for which the current capacitance value is less than the lower limit capacitance threshold being greater than or equal to a second preset time; the first preset time is greater than the second preset time.

2. The liquid level detection device according to claim 1, characterized in that, Also includes: Power module; The power module is used to convert the external power supply voltage into the internal power supply voltage and supply power to the capacitor acquisition circuit and the controller respectively.

3. The liquid level detection device according to claim 2, characterized in that, The capacitance acquisition circuit includes a first transistor, a second transistor, a reference capacitor, a first charging resistor, a second charging resistor, a first current-limiting resistor, and a second current-limiting resistor. The emitter of the first transistor is electrically connected to the power module through the first current-limiting resistor, the collector of the first transistor is grounded, and the base of the first transistor is electrically connected to the power module through the second charging resistor. The emitter of the second transistor is electrically connected to the power module through the second current-limiting resistor, the collector of the second transistor is grounded, and the base of the second transistor is electrically connected to the power module through the first charging resistor. The reference capacitor is electrically connected between the emitter of the first transistor and the base of the second transistor, and the probe capacitor is electrically connected between the emitter of the second transistor and the base of the first transistor. The emitter of the second transistor is the capacitance detection signal output terminal of the capacitance acquisition circuit.

4. The liquid level detection device according to claim 3, characterized in that, The controller is further configured to determine the current capacitance value of the probe capacitor based on a first calculation formula, according to the period of the capacitance detection signal, the resistance value of the first charging resistor, the resistance value of the second charging resistor, and the capacitance value of the reference capacitor. The first calculation formula is: ； in, The period of the capacitance detection signal is denoted as . For preset time coefficient, Let be the resistance value of the first charging resistor. The resistance value of the second charging resistor. The capacitance value of the reference capacitor. This is the current capacitance value of the probe capacitor.

5. The liquid level detection device according to claim 1, characterized in that, The controller is further configured to, after determining that the current capacitance value meets the first preset condition, if it detects that the current capacitance value is between the lower limit threshold and the upper limit threshold, control the liquid level detection output terminal to maintain the output of the first level signal; The controller is further configured to, after determining that the current capacitance value meets the second preset condition, if it detects that the current capacitance value is between the lower capacitance threshold and the upper capacitance threshold, control the liquid level detection output terminal to maintain the output of the second level signal.

6. The liquid level detection device according to claim 1, characterized in that, Also includes: Probe assembly; The probe assembly includes an inner electrode and an outer electrode disposed at least partially around the inner electrode; The inner electrode and the outer electrode are insulated from each other; the probe capacitance and the liquid level detection space are formed between the inner electrode and the outer electrode; The external electrode is provided with a first drainage through hole group and a second drainage through hole group that communicate with the liquid level detection space. The first drainage through hole group and the second drainage through hole group are respectively located on opposite sides of the external electrode. Both the first drainage through hole group and the second drainage through hole group include at least two drainage through holes, and at least two drainage through holes in the same drainage through hole group are arranged sequentially along the axial direction of the external electrode; The drainage hole is an elliptical hole.

7. The liquid level detection device according to claim 2, characterized in that, Also includes: Drive circuit; The drive circuit is electrically connected between the controller and the liquid level detection output terminal; The controller is also configured to output a high liquid level drive signal when it is determined that the current capacitance value meets the first preset condition, and to output a low liquid level drive signal when it is determined that the current capacitance value meets the second preset condition; The driving circuit is used to control the liquid level detection output terminal to output the first level signal after receiving the high liquid level driving signal, and to control the liquid level detection output terminal to output the second level signal after receiving the low liquid level driving signal. The power module is also used to supply power to the drive circuit.

8. The liquid level detection device according to claim 7, characterized in that, The driving circuit includes a first MOSFET, a first resistor, a second resistor, and a third resistor; The gate of the first MOSFET is electrically connected to the drive signal output terminal of the controller through the first resistor, and grounded through the second resistor; The source of the first MOS transistor is grounded, and the drain of the first MOS transistor is electrically connected to the liquid level detection output terminal. The liquid level detection output terminal is also electrically connected to the power module through the third resistor; When the drive signal output terminal outputs the high liquid level drive signal, the first MOS transistor is turned off, and the liquid level detection output terminal outputs a high level; when the drive signal output terminal outputs the low liquid level drive signal, the first MOS transistor is turned on, and the liquid level detection output terminal outputs a low level.

9. The liquid level detection device according to claim 8, characterized in that, The driving circuit also includes an anti-reverse diode and a transient voltage suppression diode; The anti-reverse diode is electrically connected between the drain of the first MOS transistor and the liquid level detection output terminal; the transient voltage suppression diode is electrically connected between the liquid level detection output terminal and the ground terminal.

10. The liquid level detection device according to claim 1, characterized in that, Also includes: Alarm module; The controller is also connected to the alarm module; the controller is also used to control the alarm module to sound an alarm when it is determined that the current capacitance value meets the second preset condition.

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