A single-ended voltage-stabilized liquid level signal device with adjustable hysteresis and a liquid level measuring method

Abstract

The application discloses a single-end voltage-stabilized liquid level signaler with adjustable hysteresis and a liquid level measuring method. The liquid level signaler comprises a capacitive liquid level sensor and a signal processing module. The signal processing module comprises a voltage stabilizing circuit, a virtual ground processing circuit, a liquid level sensing conversion circuit, a hysteresis comparison circuit and a signal output circuit. The liquid level sensing conversion circuit comprises a signal generating circuit, a signal excitation circuit and a comparison amplifying circuit. The voltage stabilizing circuit and the virtual ground processing circuit are respectively used for linear voltage stabilization and virtual ground generation of a single-end power supply, serving as a reference voltage of the latter circuit. The liquid level signaler only needs single-end power supply, and the fluctuation within a certain range does not affect the output of the latter, so that the quality and quantity of the on-board power supply are required to be lower. The application has controllable hysteresis comparison function and can effectively filter, so as to realize hardware dithering, greatly solve the occurrence of false alarm and have good practicability.

Description

Technical Field

[0001] This invention belongs to the technical field of liquid level detection in aerospace aircraft, specifically relating to a hysteresis-adjustable single-ended voltage-stabilized liquid level signal device and a liquid level measurement method. Background Technology

[0002] Liquid level signalers are crucial components in aerospace systems, primarily responsible for issuing alarm signals at predetermined liquid level positions. As aerospace performance improves year by year, the environmental conditions faced by liquid level signalers—including vibration, acceleration, and shock—are becoming increasingly severe, making false alarms caused by liquid level fluctuations more and more pronounced.

[0003] Traditional liquid level indicators are mostly reed switch magnetic float type. Under high-intensity environmental conditions, the float in the liquid level indicator will bounce up and down, which can easily cause false alarms. Secondly, the electronic circuit of traditional liquid level indicators is mostly located at a remote measurement point. Due to the uncontrollable parasitic capacitance of the cable, it can lead to large measurement errors, which is extremely detrimental to flight safety.

[0004] Meanwhile, the level signal devices currently used on the machine require dual positive and negative power supplies and have high requirements for power supply stability to provide a stable reference voltage. Their environmental adaptability and compatibility are relatively poor. Different operating conditions place varying requirements on the circuit measurement range and hysteresis region of the level signal device, necessitating customized products based on actual requirements, resulting in poor product reusability. Summary of the Invention

[0005] The purpose of this invention is to provide a hysteresis-adjustable single-ended voltage-stabilized liquid level signal device and a liquid level measurement method, in order to solve the above-mentioned problems.

[0006] This invention is mainly achieved through the following technical solutions:

[0007] A hysteresis-adjustable single-ended voltage-regulated liquid level signaler includes a capacitive liquid level sensor and a signal processing module; the signal processing module includes a voltage regulation circuit, a virtual ground processing circuit, a liquid level sensing conversion circuit, a hysteresis comparison circuit, and a signal output circuit; the liquid level sensing conversion circuit includes a signal generation circuit, a signal excitation circuit, and a comparison amplification circuit connected sequentially from front to back.

[0008] The voltage regulator circuit is connected to the virtual ground processing circuit. The voltage regulator circuit and the virtual ground processing circuit are used to linearly regulate the single-ended power supply and generate a virtual ground, respectively, as the reference voltage V for the subsequent circuit. ref ;

[0009] The signal generation circuit is used to generate a sine wave of fixed frequency and generate a virtual ground. The sine wave serves as the excitation signal for the liquid level sensor, and the virtual ground serves as the reference for the operational amplifier of the subsequent liquid level sensing conversion circuit. The output terminal of the liquid level sensor is connected to the signal excitation circuit and the comparison amplifier circuit.

[0010] The comparison amplifier circuit is used to process and output a stable first voltage signal that is related to the immersion depth of the liquid level sensor.

[0011] The hysteresis comparator circuit is used to compare the first voltage signal with the reference voltage V. ref By comparison, a second voltage signal is obtained.

[0012] The inverter is used to process the second voltage signal to obtain the third voltage signal, and the signal output circuit is used to identify the third voltage signal to obtain the ground / on signal.

[0013] To better realize the present invention, the signal excitation circuit further includes diodes V1 and V2, a liquid level sensing capacitor Cx, reference adjustment resistors R1 and R2, and an operational amplifier U4; the output signal of the sensing capacitor of the liquid level sensor is respectively input to the negative terminal of diode V1 and the positive terminal of diode V2; the positive terminal of diode V1 and the negative terminal of diode V2 are respectively connected to the negative input terminal and the positive input terminal of operational amplifier U4; the reference adjustment resistors R1 and R2 are connected in series, and the two ends of the reference adjustment resistor R1 are respectively connected to a reference voltage V. ref The negative input terminal of operational amplifier U4 and the two ends of reference adjustment resistor R2 are connected to the positive input terminal and the output terminal of operational amplifier U4, respectively.

[0014] To better realize the present invention, furthermore, when the reference adjustment resistor R2 is increased by X times, the voltage adjustment range of the comparator amplifier circuit increases by X times; when the reference adjustment resistor R1 is increased by X times, the voltage adjustment range of the comparator amplifier circuit increases... times.

[0015] To better realize the present invention, the hysteresis comparator circuit further includes a hysteresis comparator and proportional adjustment resistors R3 and R4. The first voltage signal is connected to the negative input terminal of the hysteresis comparator, and the reference voltage V is connected to both ends of the reference adjustment resistor R3. ref The reference adjustment resistor R4 is connected to the positive input terminal of the hysteresis comparator and the output terminal of the hysteresis comparator, respectively.

[0016] To better implement the present invention, the output swing of the hysteresis comparator is further defined as (0, V). cc -V 特性 The upper threshold of the hysteresis zone is:

[0017]

[0018] The lower threshold of the hysteresis region is:

[0019]

[0020] Where: V cc Supply voltage to the hysteresis comparator;

[0021] V 特性 The characteristic voltage drop of the hysteresis comparator device;

[0022] When the first voltage signal is greater than the upper threshold of the hysteresis region, the second voltage signal is 0V; when the first voltage signal is less than the lower threshold of the hysteresis region, the second voltage signal is V. cc -V 特性 When the first voltage signal is the upper threshold or lower threshold of the hysteresis region, the corresponding immersion height of the liquid level sensor is h, respectively. 迟滞上 or h 迟滞下 .

[0023] To better realize the present invention, the signal output circuit further includes a current-limiting resistor R5, a MOSFET D1, and a diode V3. The third voltage signal is connected to the gate (G) terminal of the MOSFET D1 through the current-limiting resistor R5, and the source (S) terminal of the MOSFET D1 is grounded. The drain (D) terminal of the MOSFET D1 outputs a ground / on signal to the outside through the diode V3.

[0024] To better realize the present invention, the upper end of the signal device is provided with a sealing mechanism, and the lower end of the signal device is provided with a liquid level sensor; the sealing mechanism includes a housing and an end face flange, the top of the end face flange is provided with the housing, the top of the housing is equipped with a sealing connector, and a printed circuit board is installed inside the housing, and the signal processing module is disposed on the printed circuit board; the housing and the end face flange, as well as the housing and the sealing connector, are sealed by oil-resistant O-rings.

[0025] To better realize the present invention, the sealing mechanism further includes an upper electrode plate assembly, a lower electrode plate assembly, an electrode plate pressure plate, an electrode plate frame, and an electrode plate pad. The bottom of the end face flange is provided with an electrode plate pad, an electrode plate frame, and an electrode plate pressure plate from top to bottom. The upper electrode plate assembly and the lower electrode plate assembly are respectively installed transversely through the electrode plate pad and the electrode plate pressure plate. The upper electrode plate assembly and the lower electrode plate assembly are respectively sealed to the electrode plate pad, the electrode plate frame, and the electrode plate pressure plate by oil-resistant O-rings. A lead-through sealing cavity is provided between the electrode plate pressure plate and the end face flange, and the sealing cavity is filled with oil-resistant sealant to fix and protect the lead-out wire of the electrode plate assembly.

[0026] This invention is mainly achieved through the following technical solutions:

[0027] A liquid level measurement method, using the aforementioned hysteresis-adjustable single-ended voltage-stabilized liquid level signal device, includes the following steps:

[0028] Step S1: A sine wave of fixed frequency is generated by the signal generation circuit as the excitation signal of the liquid level sensor, and a virtual ground is generated as the reference of the operational amplifier of the subsequent liquid level sensing conversion circuit.

[0029] Step S2: The voltage regulator circuit is connected before the virtual ground processing circuit to linearly regulate the single-ended power supply and simultaneously generate a virtual ground of 0.5W, which serves as the reference voltage V for the subsequent circuit. ref ;

[0030] Step S3: Excite the liquid level sensor with a sine wave, and then pass it through the signal excitation circuit and the comparison amplification circuit in sequence to obtain a first voltage signal related to the immersion depth of the liquid level sensor;

[0031] Step S4: Use a hysteresis comparator circuit to compare the first voltage signal with the reference voltage V. ref The comparison is performed to obtain the second voltage signal;

[0032] Step S5: Use an inverter to process the second voltage signal to obtain the third voltage signal;

[0033] Step S6: Use the signal output circuit to identify the third voltage signal to obtain the ground / open signal, and then send it to the host computer for processing to obtain the liquid level height.

[0034] The beneficial effects of this invention are as follows:

[0035] The liquid level signal of this invention only requires a single-ended power supply, and fluctuations within a certain range do not affect the output of subsequent stages, thus having low requirements for the quality and quantity of the on-board power supply. The circuit measurement range can be adjusted by changing the reference adjustment resistors R1 and R2 to adapt to various application scenarios. The hysteresis region of the liquid level signal can be practically adjusted by changing the proportional adjustment resistors R3 and R4, and it has a controllable hysteresis comparison function, which can effectively filter and thus achieve hardware debouncing, greatly solving the problem of false alarms.

[0036] This invention allows adjustment of the capacitance range at the signal point by adjusting the spacing between the two plates. The invention features a simple structure, small size, and light weight; it requires only a sealed space and a level sensor to form a level signal device. Its operating environment is not limited by the special structure of the oil tank, and its size is more than 70% smaller than that of a reed float-type signal device.

[0037] The liquid level signal of this invention features a fully internal structure, allowing it to measure higher liquid levels than reed float-type signal devices. Structurally, it is positioned as close as possible to the full liquid level signal location on the aircraft. This invention directly converts oil level information into a ground / open signal and outputs it to the electromechanical management computer or other host computer systems. It is unaffected by the parasitic capacitance of the measuring cable, exhibits minimal signal error, and has virtually no signal delay. This invention features a lead-sealed cavity, effectively ensuring the isolation of the circuit board and components from the liquid while guaranteeing signal transmission, thus meeting the operational requirements of aircraft during maneuvering flight. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the overall structure of the hysteresis-adjustable single-ended voltage-stabilized liquid level signal device of the present invention.

[0039] Figure 2 This is a circuit diagram of the liquid level sensing and conversion circuit of the present invention;

[0040] Figure 3 This is a circuit diagram of the hysteresis comparator circuit of the present invention;

[0041] Figure 4 This is a circuit diagram of the signal output circuit of the present invention.

[0042] In the diagram: 1-Electrode plate frame, 2-Electrode plate pad, 3-Printed circuit board, 4-Electrode plate pressure plate, 5-Upper electrode plate assembly, 6-Lower electrode plate assembly, 7-End face flange, 8-Housing shell, 9-Sealed connector. Detailed Implementation

[0043] Example 1:

[0044] A hysteresis-adjustable single-ended voltage-regulated liquid level signaler includes a liquid level sensor and electronic hardware components (printed circuit board 3). The liquid level sensor adopts a capacitive measurement principle. Unlike the cylindrical capacitor structure of an oil level sensor, the liquid level sensor has a parallel plate capacitor structure, with two layers of metal plates forming a sensitive element to sense the oil level height. When the medium ratio between the parallel plates changes, the capacitance of the cylindrical capacitor changes, thereby outputting a capacitive signal corresponding to the oil level height.

[0045] The electronic hardware section (printed circuit board 3) converts the capacitance into a voltage signal and outputs it to the host computer. Printed circuit board 3 includes a voltage regulator circuit, a virtual ground processing circuit, a liquid level sensing conversion circuit, a hysteresis comparison circuit, and a signal output circuit. First, a constant sine wave is generated to periodically excite the sensor, outputting a voltage signal proportional to the liquid level height. Then, after passing through the voltage regulator circuit, virtual ground processing circuit, liquid level sensing conversion circuit, hysteresis comparison circuit, and signal output circuit, a ground / on signal is output externally.

[0046] Preferably, such as Figure 2As shown, the liquid level sensing and conversion circuit includes a signal generation circuit, a signal excitation circuit, and a comparison and amplification circuit; the signal generation circuit, liquid level sensor, signal excitation circuit, and comparison and amplification circuit are connected sequentially from front to back. The distance between the two plates of the liquid level sensor is H, and the immersion height of the liquid level sensor is h.

[0047] Specifically, the signal generation circuit includes a crystal oscillator G1, a counter R1, and dual operational amplifiers U2 and U3; the crystal oscillator G1, the counter R1, and the dual operational amplifiers U2 and U3 are connected in sequence to generate a sine wave of a fixed frequency as the excitation signal for the liquid level sensor.

[0048] u(t) = U0 × cos2πft

[0049] Where u(t) is the excitation signal of the liquid level sensor;

[0050] U0 is the reference voltage for the dual operational amplifiers U2 and U3;

[0051] f is the frequency of crystal oscillator G1;

[0052] t is the counting time of counter R1;

[0053] Specifically, the signal excitation circuit includes diodes V1 and V2, a liquid level sensing capacitor Cx, reference adjustment resistors R1 and R2, and an operational amplifier U4. After the fixed-frequency sinusoidal wave excites the capacitor Cx of the liquid level sensor, it is connected to the negative terminal of diode V1 and the positive terminal of diode V2, respectively. The impedance of this part is defined as Zc.

[0054]

[0055] Where: K is a constant related to diodes V1 and V2;

[0056] The positive terminal of diode V1 is connected to the negative input terminal of operational amplifier U4, and the negative terminal of diode V2 is connected to the positive input terminal of operational amplifier U4. The two ends of the reference adjustment resistor R1 are connected to the reference voltage and the negative input terminal of operational amplifier U4, respectively. The two ends of the reference adjustment resistor R2 are connected to the positive input terminal and the output terminal of operational amplifier U4, respectively. The reference adjustment resistors R1 and R2 can adjust the measurement range of the circuit.

[0057] The capacitor Cx of the liquid level sensor is excited by a sinusoidal wave. The forward current at the rear end is conducted to ground through diode V1, and the reverse current is processed into a stable DC voltage signal U0 by the subsequent filter and amplifier circuit.

[0058] The AC signal I1 that enters the subsequent stage after passing through the diode is:

[0059]

[0060] Specifically, the comparison amplification circuit includes dual operational amplifiers U5 and U6; the comparison amplification circuit is composed of dual operational amplifiers U5 and U6 connected in sequence, which processes the signal generated by the signal generation circuit and the signal excitation circuit, and outputs a stable first voltage signal with a suitable range related to the immersion depth of the liquid level sensor; the first voltage signal has a direct proportional linear correspondence with the immersion height h of the liquid level sensor.

[0061] When the immersion height h of the liquid level sensor is 0, the first voltage signal is U. 00 When the immersion height of the liquid level sensor is h, which is the distance H between the two plates of the liquid level sensor, the first voltage signal is U. 0m .

[0062] The comparator amplifier circuit is decomposed into an amplifier circuit for DC signal U1 and an amplifier circuit for AC signal U2; the amplification factor of DC signal U1 is... The amplification factor of AC signal U2 is

[0063]

[0064] That is, the first

[0065] When C = C0

[0066] When C = 2C0

[0067] therefore

[0068] Where: C is the capacitance value to be measured;

[0069] C0 is the capacitance value when the immersion height h is 0.

[0070] Therefore, we can conclude that: increasing resistor R2 by a factor of X will increase the voltage adjustment range by a factor of X; increasing resistor R1 by a factor of X will also increase the voltage adjustment range. times.

[0071] As shown in Tables 1 and 2, the simulation was conducted with both R1 and R2 increased by 10%: when R1 increases by 10%, the voltages C0 and Cm (i.e., U) are... 00 and U 0m The increase in magnitude was almost the same for all of them, and the increase was similar to that of (u). 0m -2*u 00 The ratio of X / (1+X) [Note: X is taken as 0.1 here] is also equal. When R2 increases by 10%, the voltages of C0 and C4 are both 1.1 times the original voltages.

[0072] Preferably, such as Figure 3 As shown, the hysteresis comparator circuit includes a hysteresis comparator and proportional adjustment resistors R3 and R4; the first voltage signal is connected to the negative input terminal of the hysteresis comparator; the reference adjustment resistor R3 is connected to a reference voltage V. ref The reference adjustment resistor R4 is connected to the positive input terminal of the hysteresis comparator and the output terminal of the hysteresis comparator, respectively.

[0073] The output swing of the hysteresis comparator is (0, V) cc -V 特性 );

[0074] Upper threshold of hysteresis zone:

[0075] Lower threshold of hysteresis region:

[0076] Where: V cc Supply voltage to the hysteresis comparator;

[0077] V 特性 The characteristic voltage drop of the hysteresis comparator device;

[0078] The input first voltage signal is greater than the upper threshold U of the hysteresis region. h At that time, the second voltage signal output is 0V;

[0079] The input first voltage signal is less than the lower threshold U of the hysteresis region. l At that time, the second voltage signal is output as V. cc -V 特性 ;

[0080] The hysteresis range of the liquid level sensor is defined as the immersion height of the liquid level sensor being h. 迟滞上 The immersion height of the liquid level sensor is h 迟滞下 The immersion height of the liquid level sensor is h. 迟滞上 At that time, the first voltage signal is the upper threshold U of the hysteresis region. h The immersion height of the liquid level sensor is h. 迟滞下 At that time, the first voltage signal is the lower threshold U of the hysteresis region. l .

[0081] Preferably, such as Figure 4 As shown, the signal output circuit includes a current-limiting resistor R5, a MOSFET D1, and a diode V1; the third voltage signal is connected to the gate (G) terminal of the MOSFET D1 through the current-limiting resistor R5; the source (S) terminal of the MOSFET D1 is grounded; the drain (D) terminal of the MOSFET D1 outputs a ground / on signal to the outside through the diode V3.

[0082] Preferably, such as Figure 1As shown, the mechanical part of the liquid level signal device includes a sealing mechanism and a liquid level sensor. The sealing mechanism mainly consists of a sealing connector 9, a housing 8, an oil-resistant O-ring, a printed circuit board 3, an end flange 7, an upper electrode assembly 5, a lower electrode assembly 6, an electrode pad 2, an electrode frame 1, and an electrode pressure plate 4, etc., and is used to isolate and protect the internal printed circuit board 3. The signal device adopts a sealed design to seal the printed circuit board 3 inside the housing 8.

[0083] Specifically, the upper part of the sealing mechanism mainly consists of a housing 8, an oil-resistant O-ring, a connector, and an end-face flange 7. The end-face flange 7 is located at the bottom of the housing 8, and the connector is mounted on the top of the housing 8. Oil-resistant O-rings seal both the housing 8 and the end-face flange 7, as well as the housing 8 and the connector. The lower part of the sealing mechanism mainly consists of an end-face flange 7, an electrode assembly, an oil-resistant O-ring, an electrode pad 2, an electrode frame 1, and an electrode pressure plate 4. Oil-resistant O-rings seal between the electrode assembly and the electrode pad 2, electrode frame 1, and electrode pressure plate 4. The sealing mechanism has a lead-through sealing cavity, and an oil-resistant sealant is filled into the cavity at the lower end of the sealing mechanism to fix and protect the lead-through wire of the electrode assembly and to provide a double seal. Thus, a sealed cavity is formed inside the signal device, effectively isolating it from external fuel.

[0084] The liquid level signal of this invention requires only a single-ended power supply, and fluctuations within a certain range do not affect the output of subsequent stages. The measurement range of the circuit can be adjusted by changing the reference adjustment resistors R1 and R2, and the hysteresis region of the liquid level signal can be practically adjusted by changing the proportional adjustment resistors R3 and R4. It has a controllable hysteresis comparison function and can perform effective filtering. At the same time, the product has a fully internal structure, which can measure higher liquid levels than reed float type signal devices. It directly converts oil level information into a ground / open signal and outputs it to the electromechanical management computer or other host computer system. It is not affected by the parasitic capacitance of the measuring cable. The product has a leadable sealed cavity, which effectively ensures the isolation of the circuit board and components from the liquid while ensuring signal transmission.

[0085] Table 1

[0086]

[0087] Table 2

[0088]

[0089] Example 2:

[0090] A liquid level measurement method, using the aforementioned hysteresis-adjustable single-ended voltage-stabilized liquid level signal device, includes the following steps:

[0091] Step 1: Generate a sine wave of fixed frequency through the signal generation circuit as the excitation signal of the liquid level sensor, and at the same time generate a virtual ground as the reference of the subsequent operational amplifier.

[0092] Step 2: Stabilize and filter the power supply and virtual ground using a voltage regulator circuit;

[0093] Step 3: Excite the liquid level sensor with a sine wave, and obtain the first voltage signal related to the immersion depth of the liquid level sensor through a comparison and amplification circuit;

[0094] Step 4: Use a hysteresis comparator to compare the voltage signal from step 3 with the reference voltage to obtain a second voltage signal representing the comparison result;

[0095] Step 5: Use an inverter to process the second voltage signal representing the comparison result in Step 4 to obtain the third voltage signal;

[0096] Step 6: Use the signal output circuit to identify the third voltage signal from Step 5 to obtain the ground / on signal. This invention converts oil level information into a ground / on signal and outputs it to the electromechanical management computer or other host computer system, unaffected by the parasitic capacitance of the measuring cable.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A hysteresis-adjustable single-ended voltage-stabilized liquid level signal device, characterized in that, The system includes a capacitive liquid level sensor and a signal processing module; the signal processing module includes a voltage regulator circuit, a virtual ground processing circuit, a liquid level sensing conversion circuit, a hysteresis comparison circuit, and a signal output circuit; the liquid level sensing conversion circuit includes a signal generation circuit, a signal excitation circuit, and a comparison amplification circuit connected sequentially from front to back. The voltage regulator circuit is connected to the virtual ground processing circuit. The voltage regulator circuit and the virtual ground processing circuit are used to linearly regulate the single-ended power supply and generate a virtual ground, respectively, as the reference voltage V for the subsequent circuit. ref ; The signal generation circuit is used to generate a sine wave of fixed frequency and generate a virtual ground. The sine wave serves as the excitation signal for the liquid level sensor, and the virtual ground serves as the reference for the operational amplifier of the subsequent liquid level sensing conversion circuit. The output terminal of the liquid level sensor is connected to the signal excitation circuit and the comparison amplifier circuit. The comparison amplifier circuit is used to process and output a stable first voltage signal that is related to the immersion depth of the liquid level sensor. The hysteresis comparator circuit is used to compare the first voltage signal with the reference voltage V. ref The second voltage signal is obtained by comparison. The inverter is used to process the second voltage signal to obtain the third voltage signal. The signal output circuit is used to identify the third voltage signal to obtain the ground / on signal.

2. The hysteresis-adjustable single-ended voltage-stabilized liquid level signal device according to claim 1, characterized in that, The signal excitation circuit includes diodes V1 and V2, a liquid level sensing capacitor Cx, reference adjustment resistors R1 and R2, and an operational amplifier U4. The output signal of the sensing capacitor of the liquid level sensor is input to the negative terminal of diode V1 and the positive terminal of diode V2, respectively. The positive terminal of diode V1 and the negative terminal of diode V2 are connected to the negative input terminal and the positive input terminal of operational amplifier U4, respectively. The reference adjustment resistors R1 and R2 are connected in series, and the two ends of the reference adjustment resistor R1 are connected to a reference voltage V. ref The negative input terminal of operational amplifier U4 and the two ends of reference adjustment resistor R2 are connected to the positive input terminal and the output terminal of operational amplifier U4, respectively.

3. The hysteresis-adjustable single-ended voltage-stabilized liquid level signal device according to claim 2, characterized in that, When the reference adjustment resistor R2 is increased by a factor of X, the voltage adjustment range of the comparator amplifier circuit increases by a factor of X; when the reference adjustment resistor R1 is increased by a factor of X, the voltage adjustment range of the comparator amplifier circuit increases by a factor of X. When the immersion height h of the liquid level sensor is 0, the first voltage signal is U. 00 When the immersion height of the liquid level sensor is h, which is the distance H between the two plates of the liquid level sensor, the first voltage signal is U. 0m .

4. The hysteresis-adjustable single-ended voltage-stabilized liquid level signal device according to claim 1, characterized in that, The hysteresis comparator circuit includes a hysteresis comparator and proportional adjustment resistors R3 and R4. The first voltage signal is connected to the negative input terminal of the hysteresis comparator, and the two ends of the proportional adjustment resistor R3 are respectively connected to the reference voltage V. ref The positive input terminal of the hysteresis comparator is connected to the positive input terminal of the hysteresis comparator and the output terminal of the hysteresis comparator, respectively.

5. A hysteresis-adjustable single-ended voltage-stabilized liquid level signal device according to claim 4, characterized in that, The output swing of the hysteresis comparator is (0, V) cc -V 特性 The upper threshold of the hysteresis zone is: The lower threshold of the hysteresis region is: Where: V cc Supply voltage to the hysteresis comparator; V 特性 The characteristic voltage drop of the hysteresis comparator device; When the first voltage signal is greater than the upper threshold of the hysteresis region, the second voltage signal is 0V; when the first voltage signal is less than the lower threshold of the hysteresis region, the second voltage signal is V. cc -V 特性 When the first voltage signal is the upper threshold or lower threshold of the hysteresis region, the corresponding immersion height of the liquid level sensor is h, respectively. 迟滞上 or h 迟滞下 .

6. A hysteresis-adjustable single-ended voltage-stabilized liquid level signal device according to claim 1, characterized in that, The signal output circuit includes a current-limiting resistor R5, a MOSFET D1, and a diode V3. The third voltage signal is connected to the gate (G) terminal of the MOSFET D1 through the current-limiting resistor R5, and the source (S) terminal of the MOSFET D1 is grounded. The drain (D) terminal of the MOSFET D1 outputs a ground / on signal to the outside through the diode V3.

7. A hysteresis-adjustable single-ended voltage-stabilized liquid level signal device according to claim 1, characterized in that, The upper end of the signal device is provided with a sealing mechanism, and the lower end of the signal device is provided with a liquid level sensor; the sealing mechanism includes a housing (8) and an end face flange (7), the top of the end face flange (7) is provided with the housing (8), the top of the housing (8) is installed with a sealing connector (9), and a printed circuit board (3) is installed inside, and the signal processing module is set on the printed circuit board (3); the housing (8) and the end face flange (7) and the housing (8) and the sealing connector (9) are sealed by oil-resistant O-rings.

8. A hysteresis-adjustable single-ended voltage-stabilized liquid level signal device according to claim 7, characterized in that, The sealing mechanism further includes an upper electrode assembly (5), a lower electrode assembly (6), an electrode pressure plate (4), an electrode frame (1), and an electrode pad (2). The bottom of the end flange (7) is provided with an electrode pad (2), an electrode frame (1), and an electrode pressure plate (4) from top to bottom. The upper electrode assembly (5) and the lower electrode assembly (6) are respectively installed horizontally through the electrode pad (2) and the electrode pressure plate (4). The upper electrode assembly (5) and the lower electrode assembly (6) are respectively sealed to the electrode pad (2), the electrode frame (1), and the electrode pressure plate (4) by oil-resistant O-rings. A lead-in sealing cavity is provided between the electrode pressure plate (4) and the end flange (7), and the sealing cavity is filled with oil-resistant sealant to fix and protect the lead wire of the electrode assembly.

9. A liquid level measurement method, using a hysteresis-adjustable single-ended voltage-stabilized liquid level signal device as described in any one of claims 1-8, characterized in that, Includes the following steps: Step S1: A sine wave of fixed frequency is generated by the signal generation circuit as the excitation signal of the liquid level sensor, and a virtual ground is generated as the reference of the operational amplifier of the subsequent liquid level sensing conversion circuit. Step S2: The voltage regulator circuit is connected before the virtual ground processing circuit to linearly regulate the single-ended power supply and simultaneously generate a virtual ground of 0.5W, which serves as the reference voltage V for the subsequent circuit. ref ; Step S3: Excite the liquid level sensor with a sine wave, and then pass it through the signal excitation circuit and the comparison amplification circuit in sequence to obtain a first voltage signal related to the immersion depth of the liquid level sensor; Step S4: Use a hysteresis comparator circuit to compare the first voltage signal with the reference voltage V. ref The comparison is performed to obtain the second voltage signal; Step S5: Use an inverter to process the second voltage signal to obtain the third voltage signal; Step S6: Use the signal output circuit to identify the third voltage signal to obtain the ground / open signal, and then send it to the host computer for processing to obtain the liquid level height.

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