Liquid level detection device and liquid level switch

Abstract

The utility model discloses an embodiment of liquid level detection device and liquid level switch. The liquid level detection device comprises measurement probe, reference capacitor and processing circuit, measurement probe sets up in the container of holding the liquid to be measured, reference capacitor has the reference capacitor value of preset, processing circuit includes detection circuit, reference circuit and microprocessor, detection circuit is used to gather to measurement probe, generates first frequency signal, reference circuit is used to gather to reference capacitor, generates second frequency signal, and microprocessor is used to obtain the probe capacitor value of measurement probe according to reference capacitor value, first frequency signal and second frequency signal. The utility model embodiment provides a kind of liquid level detection device and liquid level switch, which realizes synchronous cancellation of environmental influence through the symmetrical design of reference circuit and detection circuit, thereby improving the reliability and anti-interference ability of detection, solving the problem of low sensor precision caused by circuit error and environmental change, and being easy to be interfered.

Description

Technical Field

[0001] This utility model relates to the field of liquid level sensor technology, and in particular to a liquid level detection device and a liquid level switch. Background Technology

[0002] Engines and electric drive axles require engine oil to reduce friction loss and aid in cooling. Submerged oil-cooled energy storage units require liquid cooling oil to cool the battery pack. Therefore, an oil level switch is needed to monitor the oil level. It outputs a normal signal when the level is high and an alarm signal when oil loss or leakage causes the level to drop.

[0003] Existing capacitive oil level switches require converting the sensor's capacitive signal into an electrical signal for monitoring and processing. This inevitably involves the use of numerous electronic components to build the signal conversion circuit. Since electronic components themselves have inherent errors, the extensive use of these components introduces significant hardware circuit errors into the signal acquisition and conversion circuit, reducing the sensor's accuracy. Furthermore, because electronic components exhibit a significant temperature drift effect, changes in temperature introduce substantial temperature drift errors into the capacitive signal acquisition and conversion circuit, further degrading the sensor's accuracy under varying temperatures. Utility Model Content

[0004] This invention provides a liquid level detection device and a liquid level switch. By setting a reference circuit, it solves the problems of low sensor accuracy and susceptibility to interference caused by circuit errors and environmental changes.

[0005] In a first aspect, this utility model provides a liquid level detection device, including a measuring probe, a reference capacitor, and a processing circuit;

[0006] The measuring probe is placed in the container holding the liquid to be measured;

[0007] The reference capacitor has a preset reference capacitance value;

[0008] The processing circuitry includes a detection circuit, a reference circuit, and a microprocessor;

[0009] The detection circuit is electrically connected to the measurement probe. The detection circuit is used to acquire data from the measurement probe and generate a first frequency signal.

[0010] The reference circuit is electrically connected to the reference capacitor. The reference circuit is used to acquire data from the reference capacitor and generate a second frequency signal.

[0011] The microprocessor is electrically connected to the detection circuit and the reference circuit respectively. The microprocessor is used to receive the first frequency signal and the second frequency signal, and to obtain the probe capacitance value of the measuring probe based on the reference capacitance value, the first frequency signal and the second frequency signal.

[0012] Optionally, the reference circuit includes a first Schmitt inverter and a sixth resistor;

[0013] The power supply terminal of the first Schmitt inverter is connected to the first power supply; the output terminal and input terminal of the first Schmitt inverter are shorted by the sixth resistor, and the input terminal of the first Schmitt inverter is grounded through the reference capacitor;

[0014] The detection circuit includes a third Schmitt inverter and a ninth resistor;

[0015] The power supply terminal of the third Schmitt inverter is connected to the second power supply; the output terminal and input terminal of the third Schmitt inverter are shorted by the ninth resistor, and the input terminal of the third Schmitt inverter is electrically connected to the measurement probe.

[0016] Optionally, the reference circuit also includes a second Schmitt inverter; the input of the second Schmitt inverter is connected to the output of the first Schmitt inverter.

[0017] The detection circuit also includes a fourth Schmitt inverter; the input of the fourth Schmitt inverter is connected to the output of the second Schmitt inverter.

[0018] Optionally, the reference circuit also includes an eighth capacitor; the first power supply is also grounded via the eighth capacitor.

[0019] The detection circuit also includes a tenth capacitor; the second power supply is also grounded via the tenth capacitor.

[0020] Optionally, a fourth resistor and a seventh resistor may also be included;

[0021] The fourth resistor is placed between the output terminal of the first Schmitt inverter and the input terminal of the second Schmitt inverter;

[0022] The seventh resistor is placed between the output of the third Schmitt inverter and the input of the fourth Schmitt inverter.

[0023] Secondly, this utility model embodiment also provides a liquid level switch, including any of the liquid level detection devices in the first aspect, and further including a status output circuit;

[0024] The status output circuit is electrically connected to the microprocessor;

[0025] The microprocessor is also used to control the state output circuit to output a first state signal when the probe capacitance value is greater than or equal to a preset capacitance threshold, or to control the state output circuit to output a second state signal when the probe capacitance value is less than the preset capacitance threshold.

[0026] Optionally, the microprocessor is also configured to control the state output circuit to output a second state signal when the first frequency signal exceeds the first preset frequency range, or when the second frequency signal exceeds the second preset frequency range.

[0027] Optionally, the status output circuit includes: a low-side control chip, a tenth resistor, a second diode, and a bidirectional transient voltage suppressor diode;

[0028] The low-side control chip has a ground terminal, an input terminal, and a control terminal.

[0029] The control terminal of the low-side control chip is electrically connected to the microprocessor, and the ground terminal of the low-side control chip is grounded.

[0030] The tenth resistor is electrically connected to the third power supply;

[0031] The tenth resistor is electrically connected to the first terminal of the second diode, and the second terminal of the second diode is electrically connected to the input terminal of the low-side control chip; wherein, the second diode conducts unidirectionally from the first terminal to the second terminal;

[0032] One end of the bidirectional transient voltage suppressor diode is electrically connected to the input terminal of the low-side control chip, and the other end is grounded;

[0033] The input terminal of the low-side control chip serves as the output terminal of the status output circuit, used to output the first status signal or the second status signal.

[0034] Optionally, assembly components may also be included;

[0035] The assembly components include connectors, circuit boards, and housings;

[0036] The circuit board is sealed inside the housing, and the processing circuitry of the liquid level detection device is integrated on the circuit board.

[0037] The connector is fixed to the housing;

[0038] The connector contains connector terminals;

[0039] One end of the connector terminal is electrically connected to the circuit board, and the other end extends into the connector for outputting electrical signals.

[0040] The measuring probe in the liquid level detection device is fixed to the side of the housing away from the connector;

[0041] The measuring probe includes a first electrode and a second electrode that form a capacitor structure with each other; the measuring probe has a first capacitance value when it is in the liquid to be measured and a second capacitance value when it is in the air.

[0042] Optionally, the measuring probe may also include an insulating sleeve fitted between the first and second electrodes.

[0043] This utility model provides a liquid level detection device, including a measuring probe, a reference capacitor, and a processing circuit. The measuring probe is disposed in a container holding the liquid to be measured and is used to sense changes in liquid level and convert them into changes in capacitance. The reference capacitor has a preset reference capacitance value. The processing circuit includes a detection circuit, a reference circuit, and a microprocessor. The detection circuit is electrically connected to the measuring probe and is used to acquire data from the measuring probe to generate a first frequency signal. The reference circuit is used to acquire data from the reference capacitance to generate a second frequency signal. The microprocessor is electrically connected to both the detection circuit and the reference circuit. The microprocessor receives the first frequency signal and the second frequency signal, and derives the real-time capacitance value of the measuring probe by calculating the frequency ratio of the first and second frequency signals and combining it with the known reference capacitance value. The liquid level detection device provided by this utility model achieves synchronous cancellation of environmental influences through the symmetrical design of the reference circuit and the detection circuit, fundamentally solving common interference problems such as temperature drift, so that the frequency difference between the first and second frequency signals is determined only by the actual capacitance change of the measuring probe. This enables high-precision and high-stability judgment of whether the liquid level exceeds the position of the measuring probe, improving the reliability and anti-interference capability of the detection. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of a liquid level detection device provided in an embodiment of the present invention;

[0045] Figure 2 This is a circuit schematic diagram of a processing circuit provided in an embodiment of the present utility model;

[0046] Figure 3 This is a schematic diagram of another liquid level detection device provided in this embodiment of the present invention;

[0047] Figure 4 This is a circuit diagram of a status output circuit provided in an embodiment of the present invention;

[0048] Figure 5 This is a schematic diagram of the structure of a liquid level switch provided in an embodiment of the present invention;

[0049] Figure 6 This is an exploded view of a liquid level switch provided in an embodiment of this utility model;

[0050] Figure 7 This is a schematic diagram of the structure of a liquid level switch in the working state provided by an embodiment of the present invention. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, not the entire structure.

[0052] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model 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 utility model 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.

[0053] Figure 1 This is a structural schematic diagram of a liquid level detection device provided in an embodiment of this utility model. Figure 1 As shown, this embodiment of the present invention provides a liquid level detection device, including a measuring probe 5, a reference capacitor, and a processing circuit 10;

[0054] The measuring probe 5 is placed in a container holding the liquid to be tested;

[0055] The reference capacitor has a preset reference capacitance value;

[0056] The processing circuit 10 includes a detection circuit 11, a reference circuit 12, and a microprocessor 13;

[0057] The detection circuit 11 is electrically connected to the measuring probe 5. The detection circuit 11 is used to acquire data from the measuring probe 5 and generate a first frequency signal f1.

[0058] The reference circuit is electrically connected to the reference capacitor, and the reference circuit 12 is used to acquire data from the reference capacitor and generate a second frequency signal f2.

[0059] The microprocessor 13 is electrically connected to the detection circuit 11 and the reference circuit 12 respectively. The microprocessor 13 is used to receive the first frequency signal f1 and the second frequency signal f2, and to obtain the probe capacitance value of the measuring probe according to the reference capacitance value, the first frequency signal f1 and the second frequency signal f2.

[0060] The capacitance value of the measuring probe is positively correlated with the liquid level of the liquid being measured.

[0061] Specifically, this invention utilizes the charging and discharging characteristics of a capacitor. The detection circuit 11 converts the probe capacitance into a first frequency signal f1, while the reference circuit 12 generates a second frequency signal f2 based on the reference capacitance. The microprocessor 13 receives the first frequency signal f1 from the detection circuit 11 and the second frequency signal f2 from the reference circuit 12. Since the two conversion circuits have identical characteristics, their output frequencies are inversely proportional to the input capacitance value. Therefore, the microprocessor 13 can directly calculate the probe capacitance value by calculating the ratio of these two frequencies (f2 / f1) and multiplying it by the known reference capacitance value. The specific calculation formula is: Probe capacitance value = Reference capacitance value × (f2 / f1).

[0062] It should be noted that the detection circuit 11 and the reference circuit 12 (except for the reference capacitor) adopt the same circuit topology and component specifications, and are integrated on the same circuit board 3. Through this design, when environmental factors such as temperature change, their effects on the detection circuit 11 and the reference circuit 12 are synchronous and in the same direction. This ensures that the first frequency signal f1 and the second frequency signal f2 maintain synchronous frequency changes when drift occurs, ultimately eliminating common-mode interference.

[0063] This utility model provides a liquid level detection device, including a measuring probe, a reference capacitor, and a processing circuit. The measuring probe is disposed in a container holding the liquid to be measured and is used to sense changes in liquid level and convert them into changes in capacitance. The reference capacitor has a preset reference capacitance value. The processing circuit includes a detection circuit, a reference circuit, and a microprocessor. The detection circuit is electrically connected to the measuring probe and is used to acquire data from the measuring probe to generate a first frequency signal. The reference circuit is used to acquire data from the reference capacitance to generate a second frequency signal. The microprocessor is electrically connected to both the detection circuit and the reference circuit. The microprocessor receives the first frequency signal and the second frequency signal, and derives the real-time capacitance value of the measuring probe by calculating the frequency ratio of the first and second frequency signals and combining it with the known reference capacitance value. The liquid level detection device provided by this utility model achieves synchronous cancellation of environmental influences through the symmetrical design of the reference circuit and the detection circuit, fundamentally solving common interference problems such as temperature drift, so that the frequency difference between the first and second frequency signals is determined only by the actual capacitance change of the measuring probe. This enables high-precision and high-stability judgment of whether the liquid level exceeds the position of the measuring probe, improving the reliability and anti-interference capability of the detection.

[0064] Figure 2 This is a circuit schematic diagram of a processing circuit provided in an embodiment of this utility model. (Reference) Figure 1 and Figure 2 In an optional embodiment, the reference circuit includes a first Schmitt inverter U4A and a sixth resistor R6; the ground terminal of the first Schmitt inverter U4A is grounded; the power supply terminal of the first Schmitt inverter U4A is connected to a first power supply; the first Schmitt inverter U4A charges the reference capacitor C9 when the voltage does not exceed a preset voltage, and discharges in reverse when the voltage exceeds the preset voltage; the output terminal and input terminal of the first Schmitt inverter U4A are shorted through the sixth resistor R6, and the input terminal of the first Schmitt inverter U4A is grounded through the reference capacitor C9; the sixth resistor R6 and the reference capacitor C9 form an RC oscillation structure to generate a second frequency signal f2; the detection circuit includes... The circuit includes a third Schmitt inverter U5A and a ninth resistor R9. The third Schmitt inverter U5A includes a ground terminal and a power supply terminal. The ground terminal of the third Schmitt inverter U5A is grounded. The power supply terminal of the third Schmitt inverter U5A is connected to a second power supply. The third Schmitt inverter U5A charges the measuring probe when the voltage does not exceed a preset voltage and discharges in reverse when the voltage exceeds the preset voltage. The output terminal and input terminal of the third Schmitt inverter U5A are shorted through the ninth resistor R9 to form an oscillation structure. The input terminal of the third Schmitt inverter U5A is electrically connected to the measuring probe. The ninth resistor R9 and the measuring probe constitute an RC oscillation structure to generate a first frequency signal f1.

[0065] Specifically, for the reference circuit, the output of the first Schmitt inverter U4A is fed back to its input through the sixth resistor R6, forming a positive feedback loop. Simultaneously, the input of the first Schmitt inverter U4A is grounded through the reference capacitor C9, thus forming an RC charging and discharging network with the sixth resistor R6 and the reference capacitor C9. When the circuit is operating, the reference capacitor C9 receives the voltage signal output by the first Schmitt inverter U4A through the sixth resistor R6. When the voltage across the reference capacitor C9 does not exceed the preset threshold of the first Schmitt inverter U4A, the first Schmitt inverter U4A outputs a high level and charges the reference capacitor C9. When the voltage across the reference capacitor C9 reaches the preset threshold of the first Schmitt inverter U4A, the output state of the first Schmitt inverter U4A flips to a low level, and the reference capacitor C9 discharges in reverse through the sixth resistor R6. When the voltage across the reference capacitor C9 discharges to the lower threshold of the first Schmitt inverter U4A, the output of the first Schmitt inverter U4A flips again. This cycle forms a stable oscillation, generating a second frequency signal f2. The frequency of the second frequency signal f2 is determined by the resistance value of the sixth resistor R6 and the capacitance value of the reference capacitor C9. Correspondingly, in the detection circuit, the output of the third Schmitt inverter U5A is fed back to the input of the third Schmitt inverter U5A through the ninth resistor R9, forming a positive feedback oscillation structure consistent with the reference circuit; the input of the third Schmitt inverter U5A is electrically connected to the measurement probe, so that the ninth resistor R9 and the equivalent capacitance (or the capacitive parameter it represents) of the measurement probe constitute the RC charging and discharging network of the detection end. Its operation is completely synchronized with the reference circuit: when the voltage across the equivalent capacitor of the measuring probe does not exceed the preset threshold of the third Schmitt inverter U5A, the third Schmitt inverter U5A outputs a high level and charges the equivalent capacitor of the measuring probe; when the voltage across the equivalent capacitor of the measuring probe exceeds the preset threshold of the third Schmitt inverter U5A, the output state of the third Schmitt inverter U5A flips to a low level, and the equivalent capacitor of the measuring probe discharges in reverse through the ninth resistor R9; when the voltage across the equivalent capacitor of the measuring probe changes repeatedly within the threshold range of the third Schmitt inverter U5A, the output state flips repeatedly, forming a stable oscillation and generating a first frequency signal f1. The frequency of the first frequency signal f1 is determined by the resistance value of the ninth resistor R9 and the equivalent capacitance value of the measuring probe. Since the sixth resistor R6 and the ninth resistor R9 have the same specifications, and the first Schmitt inverter U4A and the third Schmitt inverter U5A have the same parameters and are integrated on the same circuit board, the influence of environmental factors on their oscillation characteristics can be synchronously canceled. The frequency difference between the first frequency signal f1 and the second frequency signal f2 is determined only by the difference between the reference capacitor C9 and the equivalent capacitance of the measuring probe. Thus, the detection result of the measuring probe is reflected by this difference, effectively suppressing common-mode interference.

[0066] Continue to refer to Figure 2In an optional embodiment, the reference circuit further includes a second Schmitt inverter U4B; the input terminal of the second Schmitt inverter U4B is connected to the output terminal of the first Schmitt inverter U4A to perform waveform shaping on the second frequency signal f2; the detection circuit further includes a fourth Schmitt inverter U5B; the input terminal of the fourth Schmitt inverter U5B is connected to the output terminal of the third Schmitt inverter U5A to perform waveform shaping on the first frequency signal f1.

[0067] Specifically, the input of the second Schmitt inverter U4B in the reference circuit is connected to the output of the first Schmitt inverter U4A. The second Schmitt inverter U4B shapes the waveform of the second frequency signal f2 output by the first Schmitt inverter U4A to eliminate glitches, noise, or waveform distortion that may be introduced during signal transmission, making the edges of the second frequency signal f2 steeper and the waveform more regular, ensuring the accuracy of subsequent circuitry in acquiring and processing this signal. Similarly, the fourth Schmitt inverter U5B in the detection circuit optimizes the first frequency signal f1, ensuring it maintains the same regularity as the second frequency signal f2.

[0068] In one specific embodiment, reference is made to Figure 2 A fourth resistor R4 is connected between the input of the second Schmitt inverter U4B and the first Schmitt inverter U4A, and a seventh resistor R7 is connected between the input of the fourth Schmitt inverter U5B and the third Schmitt inverter U5A. In the reference circuit, the RC network containing the first Schmitt inverter U4A forms a relaxation oscillator, whose output square wave suffers from insufficiently steep rising / falling edges, ringing, or overshoot. The fourth resistor R4 suppresses overshoot by limiting current. Based on this, the second Schmitt inverter U4B shapes the signal generated by the oscillator, outputting a square wave signal with steep edges and standard digital levels, thereby effectively suppressing waveform distortion generated by the preceding stage and improving the signal's anti-interference capability and measurement accuracy. Similarly, in the detection circuit, the same current limiting and waveform shaping processing is performed through the seventh resistor R7 and the fourth Schmitt inverter U5B.

[0069] It should be noted that some inverter chips include two inverter units, which is not a limitation of this application. For example, the first Schmitt inverter U4A and the second Schmitt inverter U4B can be two independent units within the same chip package.

[0070] Continue to refer to Figure 2 In an optional embodiment, the reference circuit further includes an eighth capacitor C8; the first power supply is also grounded via the eighth capacitor C8 to stabilize the power supply voltage of the first power supply; the detection circuit further includes a tenth capacitor C10; the second power supply is also grounded via the tenth capacitor C10 to stabilize the power supply voltage of the second power supply.

[0071] Specifically, in the reference circuit, one end of the eighth capacitor C8 is connected to the first power supply, and the other end is grounded, forming a power supply filter structure. When the output voltage of the first power supply experiences ripple or noise due to load fluctuations or external interference, the eighth capacitor C8 can absorb voltage fluctuations through charging and discharging, smoothing the power supply output and ensuring a stable operating voltage for the first Schmitt inverter U4A and the second Schmitt inverter U4B, preventing power instability from causing additional drift in the second frequency signal f2. Similarly, in the detection circuit, one end of the tenth capacitor C10 is connected to the second power supply, and the other end is grounded, to prevent power instability from causing additional drift in the first frequency signal f1.

[0072] Continue to refer to Figure 1 In an optional embodiment, the microprocessor 13 is used to multiply a reference capacitance value by the ratio of a first frequency signal and a second frequency signal to obtain the probe capacitance value of the measuring probe.

[0073] For details, please refer to Figure 2 K1 is a fixed parameter of the third Schmitt inverter U5A, R9 is the resistance value of the ninth resistor, K2 is a fixed parameter of the first Schmitt inverter U4A, and R6 is the resistance value of the sixth resistor. The charging and discharging time T1 of the equivalent capacitance C1 of the measuring probe satisfies T1=K1×R9×C1, and the charging and discharging time T2 of the reference capacitor C9 satisfies T2=K2×R6×C9. Since the third Schmitt inverter U5A and the first Schmitt inverter U4A are of the same model, and the ninth resistor R9 and the sixth resistor R6 are of the same specification, K1=K2 and R9=R6. At this time, K1 and K2, and R9 and R6 can cancel each other out. By collecting T1 and T2, the calculation formula for the measuring capacitance C1 can be derived: C1=(T1×C9) / T2. This calculation method, by introducing a reference capacitor, eliminates the influence of inverter parameters, resistor specifications, and environmental factors on the measurement results, and improves the calculation accuracy of the equivalent capacitance C1 of the measuring probe. Furthermore, by comparing the frequency difference between the first frequency signal f1 and the second frequency signal f2, the capacitance change relationship between the equivalent capacitance C1 of the measuring probe and the reference capacitance C9 can be accurately reflected. Finally, based on this capacitance change, the liquid level can be accurately judged, eliminating the influence of inverter parameters, resistor specifications, and environmental factors on the measurement results.

[0074] Figure 3 This is a schematic diagram of another liquid level detection device provided in an embodiment of the present invention, for reference. Figure 3 In an optional embodiment, a power module 16 is also included. The power module 16 is electrically connected to the microprocessor 13 and is used to supply power to each module in the liquid level detection device. In other embodiments of this application, the first power supply, the second power supply, and the third power supply can all be replaced by the power module 16.

[0075] This utility model embodiment also provides a liquid level switch, including any of the liquid level detection devices in the above embodiments, and further including a status output circuit 14;

[0076] The status output circuit 14 is electrically connected to the microprocessor 13;

[0077] The microprocessor 13 is also used to control the state output circuit 14 to output a first state signal when the probe capacitance value is greater than or equal to a preset capacitance threshold, or to control the state output circuit 14 to output a second state signal when the probe capacitance value is less than the preset capacitance threshold.

[0078] The first and second state signals can be two different level signals; for example, the first state signal can be high and the second state signal can be low. The capacitance threshold can be a specific capacitance value corresponding to the alarm level, or it can be a range of capacitance values ​​reflecting the alarm level and the normal level range above it. Specifically, when the capacitance threshold is set to a range of capacitance values, the circuit can use a follow-up setting, meaning that the first state signal or normal signal will only switch when the liquid level rises from the alarm level to the normal level, and the second state signal or alarm signal will only switch when the liquid level falls from the normal level to the alarm level.

[0079] In an optional embodiment, the microprocessor 13 is further configured to control the state output circuit 14 to output a second state signal when the first frequency signal exceeds the first preset frequency range, or when the second frequency signal exceeds the second preset frequency range.

[0080] The first preset frequency range and the second preset frequency range can be understood as the normal operating threshold range of the first frequency signal and the second frequency signal, respectively. Exceeding this range indicates that the signal is abnormal.

[0081] Specifically, when the reference capacitor or the probe capacitor is damaged, the first frequency signal of the probe capacitance value will exceed the first preset frequency range, or the second frequency signal of the reference capacitor will exceed the second preset frequency range. After the microprocessor 13 detects the above abnormality, it will force the status output circuit 14 to output a second status signal (such as a low level), thereby reminding the staff to repair or add the solution to be tested.

[0082] Continue to refer to Figure 4 In an optional embodiment, the liquid level detection device further includes a power supply module 16.

[0083] For example, in this embodiment of the present invention, a low-side driver chip can be used as the status output circuit 14. The low-side driver chip integrates multiple protection functions such as short-circuit protection, overvoltage protection, overcurrent protection, and reverse connection protection, which has strong resistance to damage and can effectively improve circuit reliability.

[0084] Figure 4This is a circuit schematic diagram of a status output circuit provided in an embodiment of this utility model, for reference. Figure 4 The status output circuit 14 includes: a low-side control chip U3, a tenth resistor R10, a second diode D2, and a bidirectional transient voltage suppressor diode TVS2;

[0085] The low-side control chip U3 has a ground terminal 3, an input terminal 2, and a control terminal 1.

[0086] The control terminal 1 of the low-side control chip U3 is electrically connected to the microprocessor 13, and the ground terminal 3 of the low-side control chip U3 is grounded.

[0087] Power module 16 is electrically connected to the tenth resistor R10;

[0088] The tenth resistor R10 is electrically connected to the first terminal of the second diode D2, and the second terminal of the second diode D2 is electrically connected to the input terminal 2 of the low-side control chip U3; wherein, the second diode D2 conducts unidirectionally from the first terminal to the second terminal;

[0089] One end of the bidirectional transient voltage suppressor diode TVS2 is electrically connected to the input terminal of the low-side control chip U3, and the other end is grounded;

[0090] The input terminal 2 of the low-side control chip U3 serves as the output terminal of the status output circuit 14, used to output the first status signal or the second status signal.

[0091] Specifically, the power module 16 supplies power to the circuit through the tenth resistor R10, and the second diode D2 limits the unidirectional current flow to prevent reverse current from impacting the power module 16; the bidirectional transient voltage suppressor diode TVS2 is used to clamp the voltage within a safe range to protect the low-side control chip U3 and subsequent circuits. Based on the liquid level detection result or fault judgment, the microprocessor 13 sends corresponding control signals to the control terminal 1 of the low-side control chip U3: when a first state signal (e.g., high level, reflecting normal liquid level) needs to be output, the microprocessor 13 outputs a control signal to turn on the low-side control chip U3, and the input terminal 2 outputs the first state signal; when a second state signal (e.g., low level, reflecting low liquid level or fault alarm) needs to be output, the microprocessor 13 changes the control signal to turn off the low-side control chip U3, and the input terminal 2 outputs the second state signal, thus achieving a stable output of the liquid level status or fault signal.

[0092] In one specific embodiment, the low-side control chip U3 can be a low-side driver chip with built-in protection, possessing multiple protection functions such as reverse connection protection, overvoltage protection, overcurrent protection, and short circuit protection. Please refer to [link / reference]. Figure 4PIN1 of the low-side control chip U3 is the Control pin, which receives control signals from the microprocessor 13. When Control is high, the MOSFET inside the low-side control chip U3 is turned on; when Control is low, the MOSFET inside the low-side control chip U3 is turned off. PIN2 and PIN4 are Input pins, which are the output signal pins of the low-side control chip U3. When the MOSFET of the low-side control chip U3 is turned on, the Input pin is pulled low to GND, outputting a low level; when the MOSFET of the low-side control chip U3 is turned off, the Input pin is pulled high by VCC, outputting a high level. PIN3 is the ground GND pin of the low-side control chip U3. Point part2 can be defined as the output terminal of the low-side drive circuit.

[0093] Continue to refer to Figure 1 In an optional embodiment, a fault indication circuit 15 is further included, which is electrically connected to the microprocessor 13; the microprocessor 13 is also used to determine that the probe is faulty when the first frequency signal f1 exceeds the first preset frequency range, and control the fault indication circuit 15 to display the first fault determination signal, or to determine that the reference fault is faulty when the second frequency signal f2 exceeds the second preset frequency range, and control the fault indication circuit 15 to display the second fault determination signal.

[0094] The first preset frequency range can be understood as the reasonable fluctuation range of the first frequency signal f1 generated by the RC oscillation structure formed by the third Schmitt inverter U5A, the ninth resistor R9, and the equivalent capacitance of the measurement probe when the measuring probe and detection circuit are in normal working condition. The second preset frequency range can be understood as the reasonable fluctuation range of the second frequency signal f2 generated by the RC oscillation structure formed by the first Schmitt inverter U4A, the sixth resistor R6, and the reference capacitor C9 when the reference circuit is operating normally without faults.

[0095] Specifically, the fault indication circuit 15 is electrically connected to the microprocessor 13 and is used to receive the fault judgment signal output by the microprocessor 13 and indicate the corresponding status. During the real-time acquisition of the first frequency signal f1 and the second frequency signal f2, the microprocessor 13 compares them with preset first and second preset frequency ranges respectively. When the frequency value of the first frequency signal f1 exceeds the first preset frequency range, the microprocessor 13 determines that the measuring probe is faulty, such as probe damage, abnormal equivalent capacitance, or a faulty detection circuit connection. At this time, the microprocessor 13 sends a first fault judgment signal to the fault indication circuit 15, driving it to identify the probe fault status through a specific form, such as indicator light flashing frequency, color combination, or fault code display. Similarly, when the frequency value of the second frequency signal f2 exceeds the second preset frequency range, the microprocessor 13 determines that the reference circuit is faulty, such as reference capacitor C9 failure, abnormal first Schmitt inverter U4A, or damaged reference circuit components. At this time, the microprocessor 13 controls the fault indication circuit 15 to output a second fault determination signal. This signal uses a different indication method than the first fault determination signal, such as different flashing cycles, indicator light colors, or codes, to identify the baseline fault state. This differentiated fault indication helps users quickly locate the faulty circuit module, providing clear guidance for subsequent repair and replacement.

[0096] Continue to refer to Figure 3 In an optional embodiment, the microprocessor 13 is further configured to determine a common part fault in the system when the first frequency signal f1 exceeds the first preset frequency range and the second frequency signal f2 exceeds the second preset frequency range, and control the fault indication circuit 15 to display a third fault indication signal.

[0097] The common part of the system can be understood as a shared module or environmental factor that simultaneously affects the normal operation of the reference circuit and the detection circuit.

[0098] Specifically, if the microprocessor 13 simultaneously detects that the first frequency signal f1 exceeds the first preset frequency range and the second frequency signal f2 exceeds the second preset frequency range, it determines that there is a fault in the common part of the system. This could be due to an abnormality in the common power module or strong external interference affecting the overall circuit. When a fault in the common part of the system is determined, the microprocessor 13 sends a third fault indication signal to the fault indication circuit 15. This signal is displayed separately from the first and second fault determination signals to clearly indicate that the fault is not a problem with a single circuit module, but involves a common part of the system. This provides maintenance personnel with a more accurate basis for fault location and reduces troubleshooting time.

[0099] It should be noted that, in a specific embodiment, the fault indication circuit 15 and the status output circuit 14 share a display module, achieving functional differentiation through differentiated indication logic. For example, when using the same multi-color LED, a solid green light indicates a normal liquid level, while a solid red light indicates a liquid level alarm; a rapidly flashing red light indicates a probe fault, a slow flashing red light indicates a reference fault, and alternating red and green flashing indicates a fault in a common part of the system. For instance, in the hydraulic oil level monitoring process of large-scale intelligent manufacturing equipment, the hydraulic oil level status and system faults directly affect the equipment's operational safety. If fault types are confused, it may lead to maintenance delays, extended equipment downtime, and even serious faults such as hydraulic pump burnout due to idling or mechanical component jamming, resulting in high maintenance costs and production losses. Therefore, it is essential to clearly distinguish between "abnormal liquid level" and various "fault types" through differentiated indication logic to meet the needs of professional maintenance personnel for rapid problem location and accurate handling.

[0100] At the same time, depending on the application scenario, the indication logic may not need to be differentiated. For example, during the monitoring of vehicle oil level, most car owners cannot add oil or replace the switch themselves after seeing the alarm. Differentiated fault display may be meaningless in this application scenario. Therefore, in such application scenarios, the fault indication circuit 15 can be omitted to save costs.

[0101] Figure 5 This is a schematic diagram of the structure of a liquid level switch provided in an embodiment of this utility model. Figure 6 This is an exploded view of a liquid level switch provided in an embodiment of this utility model. Figure 7 This is a schematic diagram of the structure of a liquid level switch in the working state according to an embodiment of this utility model. (Reference) Figures 5 to 7 In an optional embodiment, the level switch further includes a level detection device and an assembly assembly;

[0102] The assembly components include connector 1, circuit board 3, and housing 4;

[0103] The circuit board 3 is sealed inside the housing 4, and the processing circuit of the liquid level detection device is integrated on the circuit board 3.

[0104] Connector 1 is fixed to housing 4;

[0105] Connector 1 is provided with connector terminal 2;

[0106] One end of connector terminal 2 is electrically connected to circuit board 3, and the other end extends into the interior of connector 1 for outputting electrical signals.

[0107] The measuring probe 5 in the liquid level detection device is fixed to the side of the housing 4 away from the connector 1;

[0108] The measuring probe 5 includes a first electrode 6 and a second electrode 8 that form a capacitor structure with each other; the measuring probe 5 has an eighth capacitance value when it is in the liquid to be measured and a second capacitance value when it is in the air.

[0109] For details, please refer to Figure 6 The housing 4 has a groove on the side opposite to the measuring probe 5, and a circuit board 3 is placed in the groove. A connector 1 is fixed to the housing 4, and the circuit board 3 is fixed between the connector 1 and the housing 4. Simultaneously, a connector terminal 2 is provided through the connector 1, and the connector terminal 2 is electrically connected to the circuit board 3. The measuring probe 5 is fixed to the other side of the housing 4 and immersed in the medium to be measured. The capacitor structure formed by the first electrode 6 and the second electrode 8 of the measuring probe 5 is electrically connected to the circuit board 3. This capacitor structure has an eighth capacitance value in the liquid to be measured and a second capacitance value in air. (Reference) Figure 7 During the operation of the liquid level switch, the liquid level switch is fixedly installed on the container holding the liquid to be measured through its housing 4. The measuring probe 5 is inserted into the container along the side wall. The set height of the measuring probe 5 determines the preset trigger position of the liquid level alarm. When the liquid level in the container drops below the preset height due to consumption, the liquid medium that originally covered the measuring probe 5 is switched to air, which causes the dielectric constant of the capacitor structure composed of the first electrode 6 and the second electrode 8 to decrease, and the capacitance value drops stepwise. The processing circuit on the circuit board 3 indicates that the liquid level has dropped below the preset height based on this capacitance change.

[0110] In an optional embodiment, the measuring probe 5 further includes an insulating sleeve 7, which is sleeved between the first electrode 6 and the second electrode 8.

[0111] Specifically, the second electrode 8 is a grounding electrode. The measuring probe 5 includes a first electrode 6, an insulating sleeve 7, and a second electrode 8, which are coaxially arranged from the inside to the outside. The insulating sleeve 7 physically isolates and electrically insulates the first electrode 6 and the second electrode 8, thereby forming a coaxial cylindrical capacitor with the insulating sleeve 7 as the dielectric among the three. When the probe is immersed in liquid, the liquid fills the space outside the second electrode 8 and changes its equivalent dielectric constant, causing a change in the overall capacitance value.

[0112] In one specific embodiment, the first electrode 6 is a copper sleeve, the second electrode 8 is a stainless steel sleeve, the stainless steel sleeve has openings distributed in its body, and the insulating sleeve 7 is a Teflon tube.

[0113] In one specific embodiment, the physical structural assembly also includes a sealing structure. The sealing structure includes: O-rings 21, ED rings 22, and sealing rings 23; two O-rings 21 are disposed in the assembly gap between the first electrode 6 and the insulating sleeve, and the ED ring 22 is disposed between the housing 4 and the first electrode 6. The ED rings 22 and the two O-rings 21 are used to prevent the solution in the container holding the liquid to be measured from seeping into the sensor along the surface of the first electrode. At the electrical interface end, the sealing ring 23 or waterproof sealant is filled at the connection between the housing 4 and the connector 1 to secure the circuit board 3.

[0114] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A liquid level detection device, characterized in that, Includes a measurement probe, a reference capacitor, and processing circuitry; The measuring probe is placed in a container holding the liquid to be measured; The reference capacitor has a preset reference capacitance value; The processing circuit includes a detection circuit, a reference circuit, and a microprocessor; The detection circuit is electrically connected to the measurement probe, and the detection circuit is used to acquire data from the measurement probe and generate a first frequency signal; The reference circuit is electrically connected to the reference capacitor, and the reference circuit is used to acquire data from the reference capacitor to generate a second frequency signal; The microprocessor is electrically connected to the detection circuit and the reference circuit respectively. The microprocessor is used to receive the first frequency signal and the second frequency signal, and to obtain the probe capacitance value of the measuring probe based on the reference capacitance value, the first frequency signal and the second frequency signal.

2. The liquid level detection device according to claim 1, characterized in that, The reference circuit includes a first Schmitt inverter and a sixth resistor; The power supply terminal of the first Schmitt inverter is connected to the first power supply; the output terminal and input terminal of the first Schmitt inverter are short-circuited through the sixth resistor, and the input terminal of the first Schmitt inverter is grounded through the reference capacitor; The detection circuit includes a third Schmitt inverter and a ninth resistor; The power supply terminal of the third Schmitt inverter is connected to the second power supply; the output terminal and input terminal of the third Schmitt inverter are shorted by the ninth resistor, and the input terminal of the third Schmitt inverter is electrically connected to the measurement probe.

3. The liquid level detection device according to claim 2, characterized in that, The reference circuit further includes a second Schmitt inverter; the input terminal of the second Schmitt inverter is connected to the output terminal of the first Schmitt inverter; The detection circuit also includes a fourth Schmitt inverter; the input terminal of the fourth Schmitt inverter is connected to the output terminal of the second Schmitt inverter.

4. The liquid level detection device according to claim 2, characterized in that, The reference circuit also includes an eighth capacitor; the first power supply is also grounded via the eighth capacitor. The detection circuit also includes a tenth capacitor; the second power supply is also grounded via the tenth capacitor.

5. The liquid level detection device according to claim 3, characterized in that, It also includes the fourth resistor and the seventh resistor; The fourth resistor is disposed between the output terminal of the first Schmitt inverter and the input terminal of the second Schmitt inverter; The seventh resistor is positioned between the output of the third Schmitt inverter and the input of the fourth Schmitt inverter.

6. A liquid level switch, characterized in that, The liquid level detection device as described in any one of claims 1-5 further includes a status output circuit; The status output circuit is electrically connected to the microprocessor; The microprocessor is also configured to control the status output circuit to output a first status signal when the probe capacitance value is greater than or equal to a preset capacitance threshold, or to control the status output circuit to output a second status signal when the probe capacitance value is less than the preset capacitance threshold.

7. The level switch according to claim 6, characterized in that, The microprocessor is further configured to control the status output circuit to output the second status signal when the first frequency signal exceeds the first preset frequency range, or when the second frequency signal exceeds the second preset frequency range.

8. The level switch according to claim 6, characterized in that, The status output circuit includes: a low-side control chip, a tenth resistor, a second diode, and a bidirectional transient voltage suppression diode; A low-side control chip, the low-side control chip having a ground terminal, an input terminal and a control terminal; The control terminal of the low-side control chip is electrically connected to the microprocessor, and the ground terminal of the low-side control chip is grounded. The tenth resistor is electrically connected to the third power supply; The tenth resistor is electrically connected to the first terminal of the second diode, and the second terminal of the second diode is electrically connected to the input terminal of the low-side control chip; wherein, the second diode conducts unidirectionally from the first terminal to the second terminal; One end of the bidirectional transient voltage suppression diode is electrically connected to the input terminal of the low-side control chip, and the other end is grounded; The input terminal of the low-side control chip serves as the output terminal of the state output circuit, used to output a first state signal or a second state signal.

9. The level switch according to claim 6, characterized in that, It also includes assembly components; The assembly assembly includes a connector (1), a circuit board (3), and a housing (4); The circuit board (3) is sealed inside the housing (4), and the processing circuit in the liquid level detection device is integrated on the circuit board (3); The connector (1) is fixed to the housing (4); The connector (1) is provided with connector terminals (2); One end of the connector terminal (2) is electrically connected to the circuit board (3), and the other end extends into the interior of the connector (1); The measuring probe (5) in the liquid level detection device is fixed to the side of the housing (4) away from the connector (1); The measuring probe (5) includes a first electrode and a second electrode that form a capacitor structure with each other.

10. The level switch according to claim 9, characterized in that, The measuring probe also includes an insulating sleeve, which is fitted between the first electrode and the second electrode.

Images