Hysteresis-adjustable single-end pressure stabilizing type liquid level annunciator and liquid level measuring method

Abstract

The invention discloses a hysteresis-adjustable single-end voltage stabilization type liquid level annunciator and a liquid level measuring method. The liquid level annunciator comprises a capacitive liquid level receptor 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 generation circuit, a signal excitation circuit and a comparison amplification circuit. And the voltage stabilizing circuit and the virtual ground processing circuit are respectively used for carrying out linear voltage stabilization on a single-end power supply and generating virtual ground as reference voltage of a post-stage circuit. The liquid level annunciator only needs a single-end power supply to supply power, the fluctuation within a certain range does not affect the post-stage output, and the requirement for the quality number of onboard power supplies is low; the method has a controllable hysteresis comparison function and can perform effective filtering, so that hardware jitter elimination is realized, the false alarm problem is solved to a great extent, and the method has relatively good practicability.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid level detection of aerospace aircraft, and in particular relates to a single-ended voltage-stabilized liquid level signal device with adjustable hysteresis and a liquid level measurement method. Background Art

[0002] The liquid level signal is an important component in the aerospace system, which is mainly responsible for sending out warning signals at the predetermined position of the liquid level. As the performance of aerospace aircraft improves year by year, the vibration, acceleration and impact environmental conditions faced by the liquid level signal are becoming more and more severe, and the false alarm problem caused by liquid level fluctuations is becoming more and more obvious.

[0003] Traditional liquid level signalers are mostly reed switch magnetic float type. Under high-intensity environmental conditions, the float in the liquid level signaler will jump up and down, which is prone to false alarms. Secondly, the electronic circuit part of the traditional liquid level signaler is mostly placed at the remote end for measurement. Since the parasitic capacitance of the cable is uncontrollable, it will cause large measurement errors, which is extremely detrimental to flight safety.

[0004] At the same time, the liquid level signal used on the aircraft now needs to be powered by both positive and negative power supplies, and has high requirements for power supply stability to provide a relatively stable reference voltage for the subsequent operation. The environmental adaptability and compatibility are relatively poor. Different usage conditions have certain differences in the circuit measurement range and hysteresis zone requirements of the liquid level signal. The product needs to be customized according to actual requirements, and the product reusability is poor. Summary of the invention

[0005] The object of the present invention is to provide a single-ended voltage-stabilized liquid level signal device with adjustable hysteresis and a liquid level measurement method, aiming to solve the above-mentioned problems.

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

[0007] A single-ended voltage-stabilized liquid level signal device with adjustable hysteresis includes a capacitive liquid level sensor and a signal processing module; the signal processing module includes a voltage stabilization 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 in sequence from front to back;

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

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

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

[0011] The hysteresis comparison circuit is used to compare the first voltage signal with the reference voltage V ref Compare and obtain the second voltage signal,

[0012] The inverter is used for processing the second voltage signal to obtain a third voltage signal, and the signal output circuit is used for identifying the third voltage signal to obtain a ground / open signal.

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

[0014] In order to better implement the present invention, further, when the reference adjustment resistor R2 is increased by X times, the voltage adjustment range of the comparison amplifier circuit is increased by X times; when the reference adjustment resistor R1 is increased by X times, the voltage adjustment range of the comparison amplifier circuit is increased times.

[0015] In order to better implement the present invention, further, the hysteresis comparison 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 reference adjustment resistor R3 are respectively connected to the reference voltage V ref and the positive input terminal of the hysteresis comparator; the two ends of the reference adjustment resistor R4 are respectively connected to the positive input terminal of the hysteresis comparator and the output terminal of the hysteresis comparator.

[0016] In order to better implement the present invention, further, the output swing of the hysteresis comparator is (0, V cc -V 特性 ), the upper threshold of the hysteresis zone is:

[0017]

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

[0019]

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

[0021] V 特性 It is the characteristic tube 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 of the hysteresis zone or the lower threshold of the hysteresis zone, the corresponding immersion height of the liquid level sensor is h 迟滞上 or 迟滞下 .

[0023] In order to better implement the present invention, further, the signal output circuit includes a current limiting resistor R5, a MOS tube D1, and a diode V3. The third voltage signal is connected to the G stage of the MOS tube D1 through the current limiting resistor R5, and the S stage of the MOS tube D1 is grounded. The D stage of the MOS tube D1 outputs a ground / open signal to the outside after passing through the diode V3.

[0024] In order to better realize the present invention, further, a sealing mechanism is provided at the upper end of the signaler, and a liquid level sensor is provided at the lower end of the signaler; the sealing mechanism includes a shell and an end face flange, a shell is provided on the top of the end face flange, a sealing connector is installed on the top of the shell, and a printed circuit board is installed inside, and the signal processing module is arranged on the printed circuit board; the shell and the end face flange and the shell and the sealing connector are sealed by oil-resistant O-rings.

[0025] In order to better realize the present invention, further, the sealing mechanism also includes an upper pole plate assembly, a lower pole plate assembly, a pole plate pressure plate, a pole plate frame and a pole plate pad. The bottom of the end face flange is sequentially provided with a pole plate pad, a pole plate frame and a pole plate pressure plate from top to bottom. The pole plate pad and the pole plate pressure plate are respectively transversely penetrated and installed with an upper pole plate assembly and a lower pole plate assembly. The upper pole plate assembly and the lower pole plate assembly are respectively sealed and connected to the pole plate pad, the pole plate frame and the pole plate pressure plate through oil-resistant O-rings; a lead-wire sealing cavity is provided between the pole plate pressure plate and the end face flange, and an oil-resistant sealant is filled in the sealing cavity to fix the lead-out wires of the protection pole plate assembly.

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

[0027] A liquid level measurement method, using the above-mentioned single-ended voltage-stabilized liquid level signal device with adjustable hysteresis, comprises the following steps:

[0028] Step S1: Generate a fixed frequency sine wave through a signal generating circuit as an excitation signal for the liquid level sensor, and generate a virtual ground as a reference for the operational amplifier of the subsequent liquid level sensing conversion circuit;

[0029] Step S2: The voltage stabilizing circuit is connected to the front stage of the virtual ground processing circuit, and the single-ended power supply is linearly stabilized and a virtual ground of 0.5W is generated at the same time, which is used as the reference voltage V of the subsequent circuit. ref ;

[0030] Step S3: using a sine wave to excite the liquid level sensor, and then obtaining a first voltage signal related to the immersion depth of the liquid level sensor through a signal excitation circuit and a comparison amplifier circuit in sequence;

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

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

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

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

[0035] The liquid level signaler of the present invention only needs a single-ended power supply, and fluctuations within a certain range do not affect the output of the subsequent stage, and the requirements for the quality and quantity of the on-board power supply are relatively low; the circuit measurement range can be adjusted by changing the reference adjustment resistors R1 and R2 to adapt to various usage scenarios; the hysteresis zone of the liquid level signaler can be practically adjusted by changing the proportional adjustment resistors R3 and R4, and it has a controllable hysteresis comparison function and can perform effective filtering, thereby realizing hardware debouncing, which greatly solves the occurrence of false alarm problems.

[0036] The present invention can adjust the capacitance range of the signal point position by adjusting the distance between the two plates. The present invention has a simple structure, a small volume, and a light weight. It only needs a sealed space and a liquid level sensor to form a liquid level signaler. Its working environment is not limited by the special structure of the oil tank. Compared with the reed float type signaler, the volume is more than 70% smaller.

[0037] The liquid level signaler of the present invention is a fully built-in structure, which can measure a higher liquid level than a reed float signaler, and is as close to the full liquid level signal position on the aircraft as possible in structure. The present invention directly converts the 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, has a small signal error, and has almost no signal delay. The present invention has a lead-in sealed cavity, which effectively ensures the isolation of circuit boards and components from liquids while ensuring signal transmission, so as to meet the use requirements of the aircraft during maneuvering flight. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the overall structure of the single-ended voltage-stabilized liquid level signal device with adjustable hysteresis according to the present invention;

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

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

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

[0042] In the figure: 1-plate frame, 2-plate pad, 3-printed circuit board, 4-plate pressure plate, 5-upper plate assembly, 6-lower plate assembly, 7-end face flange, 8-housing, 9-sealed connector. DETAILED DESCRIPTION

[0043] Embodiment 1:

[0044] A single-ended voltage-stabilized liquid level signal transmitter with adjustable hysteresis includes a liquid level sensor and an electronic hardware part (printed circuit board 3). The liquid level sensor adopts a capacitive measurement principle. Different from the columnar capacitor structure of the oil level sensor, the liquid level sensor is a parallel plate capacitor structure. A sensitive element is formed by two layers of metal plates to sense the oil level. When the medium ratio between the parallel plates changes, the capacitance of the columnar capacitor changes, thereby outputting a capacitance signal corresponding to the oil level.

[0045] The electronic hardware part (printed circuit board 3) converts the capacitance into a voltage signal and outputs it to the host computer. The printed circuit board 3 includes a voltage stabilizing 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, and a voltage signal proportional to the liquid level is output. After that, the voltage stabilizing circuit, the virtual ground processing circuit, the liquid level sensing conversion circuit, the hysteresis comparison circuit, and the signal output circuit are used to output a ground / open signal to the outside.

[0046] Preferably, if Figure 2As shown, the liquid level sensing conversion circuit includes a signal generating circuit, a signal excitation circuit and a comparison amplification circuit; the signal generating circuit, the liquid level sensor, the signal excitation circuit and the comparison amplification circuit are connected in sequence 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 generating 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 fixed-frequency sine wave as an 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 of 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 sine wave excites the capacitor Cx of the liquid level sensor, it is connected to the negative end of the diode V1 and the positive end of the diode V2 respectively, and this part of the impedance is defined as Zc:

[0054]

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

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

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

[0058] The AC signal I1 entering the next stage through the diode is:

[0059]

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

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

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

[0063]

[0064] 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, it can be concluded that if the resistor R2 is increased by X times, the voltage adjustment range will also increase by X times. If the resistor R1 is increased by X times, the voltage adjustment range will also increase. times.

[0071] As shown in Table 1 and Table 2, the simulation is performed with both R1 and R2 increasing by 10%. When R1 increases by 10%, the voltage of C0 and the voltage of Cm (i.e., U 00 and U 0m ) are almost the same, and the increase is similar to (u 0m -2*u 00 ) is also equal to X / (1+X) [Note: X is 0.1 here]. When R2 increases by 10%, the voltage of C0 and the voltage of C4 are both 1.1 times of the original voltage.

[0072] Preferably, if Figure 3 As shown, the hysteresis comparison 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 two ends of the reference adjustment resistor R3 are respectively connected to the reference voltage V ref and the positive input terminal of the hysteresis comparator; the two ends of the reference adjustment resistor R4 are respectively connected to the positive input terminal of the hysteresis comparator and the output terminal of the hysteresis comparator;

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

[0074] Hysteresis zone upper threshold:

[0075] Hysteresis lower threshold:

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

[0077] V 特性 It is the characteristic tube voltage drop of the hysteresis comparator device;

[0078] The first input voltage signal is greater than the upper threshold U of the hysteresis zone h When , the second voltage signal is output as 0V;

[0079] The input first voltage signal is less than the lower threshold U of the hysteresis zone l When the second voltage signal is output, V cc -V 特性 ;

[0080] The hysteresis interval of the liquid level sensor is h. 迟滞上 The height of the liquid level sensor is h 迟滞下 ; The liquid level sensor immersion height is h 迟滞上 When the first voltage signal is the upper threshold U of the hysteresis zone h ; The liquid level sensor immersion height is h 迟滞下 When the first voltage signal is the lower threshold U of the hysteresis region l .

[0081] Preferably, if Figure 4 As shown, the signal output circuit includes a current limiting resistor R5, a MOS tube D1, and a diode V1; the third voltage signal is connected to the G level of the MOS tube D1 through the current limiting resistor R5; the S level of the MOS tube D1 is grounded; and the D level of the MOS tube D1 outputs a ground / open signal to the outside after passing through the diode V3.

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

[0083] Specifically, the upper end of the sealing mechanism is mainly composed of a shell 8, an oil-resistant O-type sealing ring, a connector and an end face flange 7. The bottom of the shell 8 is provided with an end face flange 7, and the top of the shell 8 is used to install the connector. The shell 8 and the end face flange 7 and the shell 8 and the connector are sealed by an oil-resistant O-type sealing ring. The lower end of the sealing mechanism is mainly composed of an end face flange 7, a plate assembly, an oil-resistant O-type sealing ring, a plate pad 2, a plate frame 1 and a plate pressure plate 4. The plate assembly and the plate pad 2, the plate frame 1 and the plate pressure plate 4 are sealed by an oil-resistant O-type sealing ring. The sealing mechanism has a lead-in sealing cavity, and an oil-resistant sealant is poured into the cavity at the lower end of the sealing mechanism to fix and protect the lead-out wires of the plate assembly and play a double sealing role. At this point, a sealed cavity is formed inside the signaler, which can effectively isolate the external fuel.

[0084] The liquid level signaler of the present invention only needs a single-ended power supply, and the fluctuation within a certain range does not affect the output of the subsequent stage. The circuit measurement range can be adjusted by changing the reference adjustment resistors R1 and R2, and the hysteresis zone of the liquid level signaler 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 is a fully built-in structure, which can measure a higher liquid level than a reed float signaler, and directly converts the oil level information into a ground / open signal output to the electromechanical management computer or other host computer system, and is not affected by the parasitic capacitance of the measuring cable. The product has a lead-in 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] Embodiment 2:

[0090] A liquid level measurement method, using the above-mentioned single-ended voltage-stabilized liquid level signal device with adjustable hysteresis, comprises the following steps:

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

[0092] Step 2: Use the voltage stabilizing circuit to stabilize and filter the power supply and virtual ground;

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

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

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

[0096] Step 6: Use the signal output circuit to identify the third voltage signal in step 5 to obtain a ground / open signal. The present invention converts the oil level information into a ground / open signal and outputs it to the electromechanical management computer or other host computer system without being affected by the parasitic capacitance of the measurement cable.

[0097] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A single-ended voltage-stabilized liquid level signal device with adjustable hysteresis, characterized in that: It includes a capacitive liquid level sensor and a signal processing module; the signal processing module includes 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 includes a signal generating circuit, a signal excitation circuit and a comparison amplification circuit connected in sequence from front to back; The voltage stabilizing circuit is connected to the virtual ground processing circuit, and the voltage stabilizing circuit and the virtual ground processing circuit are respectively used to perform linear voltage stabilization on the single-ended power supply and generate a virtual ground as a reference voltage V for the subsequent circuit. ref ; The signal generating circuit is used to generate a sine wave with a fixed frequency and generate a virtual ground. The sine wave is used as an excitation signal for the liquid level sensor, and the virtual ground is used as a reference for an operational amplifier of a subsequent liquid level sensing conversion circuit. The output end of the liquid level sensor is connected to a comparison amplifier circuit via a signal excitation circuit. The comparison amplifier circuit is used to process and output a first voltage signal which is stable and related to the immersion depth of the liquid level sensor; The hysteresis comparison circuit is used to compare the first voltage signal with the reference voltage V ref Compare and obtain the second voltage signal, The inverter is used for processing the second voltage signal to obtain a third voltage signal, and the signal output circuit is used for identifying the third voltage signal to obtain a ground / open signal.

2. The single-ended voltage-stabilized liquid level signal device with adjustable hysteresis 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 respectively input to the negative end of the diode V1 and the positive end of the diode V2; the positive end of the diode V1 and the negative end of the diode V2 are respectively connected to the negative input end and the positive input end of the operational amplifier U4; the reference adjustment resistor R1 is connected in series with the reference adjustment resistor R2, and the two ends of the reference adjustment resistor R1 are respectively connected to the reference voltage V ref and the negative input terminal of the operational amplifier U4, and the two ends of the reference adjustment resistor R2 are respectively connected to the positive input terminal of the operational amplifier U4 and the output terminal of the operational amplifier U4.

3. The single-ended voltage-stabilized liquid level signal device with adjustable hysteresis according to claim 2, characterized in that: When the reference adjustment resistor R2 is increased by X times, the voltage adjustment range of the comparison amplifier circuit increases by X times; when the reference adjustment resistor R1 is increased by X times, the voltage adjustment range of the comparison amplifier circuit increases times.

4. The single-ended voltage-stabilized liquid level signal device with adjustable hysteresis according to claim 1, characterized in that: The hysteresis comparison 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 two ends of the reference adjustment resistor R3 are respectively connected to the reference voltage V ref and the positive input terminal of the hysteresis comparator; the two ends of the reference adjustment resistor R4 are respectively connected to the positive input terminal of the hysteresis comparator and the output terminal of the hysteresis comparator.

5. The single-ended voltage-stabilized liquid level signal device with adjustable hysteresis 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 zone is: Where: V cc Supply voltage for hysteresis comparator; V 特性 It is the characteristic tube 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 of the hysteresis zone or the lower threshold of the hysteresis zone, the corresponding immersion height of the liquid level sensor is h 迟滞上 or 迟滞下 .

6. The single-ended voltage-stabilized liquid level signal device with adjustable hysteresis according to claim 1, characterized in that: The signal output circuit includes a current limiting resistor R5, a MOS tube D1, and a diode V3. The third voltage signal is connected to the G stage of the MOS tube D1 through the current limiting resistor R5, and the S stage of the MOS tube D1 is grounded. The D stage of the MOS tube D1 outputs a ground / open signal to the outside after passing through the diode V3.

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

8. The single-ended voltage-stabilized liquid level signal device with adjustable hysteresis according to claim 7, characterized in that: The sealing mechanism further comprises an upper plate assembly (5), a lower plate assembly (6), a plate pressing plate (4), a plate frame (1) and a plate pad (2); the bottom of the end face flange (7) is provided with a plate pad (2), a plate frame (1) and a plate pressing plate (4) in sequence from top to bottom; the upper plate assembly (5) and the lower plate assembly (6) are respectively transversely penetrated and installed on the plate pad (2) and the plate pressing plate (4); the upper plate assembly (5) and the lower plate assembly (6) are respectively sealed and connected to the plate pad (2), the plate frame (1) and the plate pressing plate (4) through oil-resistant O-rings; a lead-wire sealing cavity is provided between the plate pressing plate (4) and the end face flange (7), and an oil-resistant sealant is filled in the sealing cavity to fix and protect the lead-out wires of the plate assembly.

9. A liquid level measurement method, using a single-ended voltage-stabilized liquid level signal device with adjustable hysteresis as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: Step S1: Generate a fixed frequency sine wave through a signal generating circuit as an excitation signal for the liquid level sensor, and generate a virtual ground as a reference for the operational amplifier of the subsequent liquid level sensing conversion circuit; Step S2: The voltage stabilizing circuit is connected to the front stage of the virtual ground processing circuit, and the single-ended power supply is linearly stabilized and a virtual ground of 0.5W is generated at the same time, which is used as the reference voltage V of the subsequent circuit. ref ; Step S3: using a sine wave to excite the liquid level sensor, and then obtaining a first voltage signal related to the immersion depth of the liquid level sensor through a signal excitation circuit and a comparison amplifier circuit in sequence; Step S4: Use a hysteresis comparison circuit to compare the first voltage signal with the reference voltage V ref Performing comparison to obtain a second voltage signal; Step S5: using an inverter to process the second voltage signal to obtain a third voltage signal; Step S6: Use the signal output circuit to identify the third voltage signal to obtain a ground / open signal, which is then sent to the host computer for processing to obtain the liquid level height.

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