Liquid level detection assembly

Abstract

The invention discloses a liquid level detection assembly, which comprises a mounting plate, the mounting plate is fixed on a base, a linear guide rail is arranged on the mounting plate, a sampling device slides up and down on the linear guide rail, a power device is fixed on the mounting plate, and the power device provides power for the sampling device. The sampling device is connected with a detection device, the detection device is used for detecting capacitance change generated when the sampling device makes contact with the liquid level, the detection device controls the sampling device to slide up and down, and high-precision detection and automatic control of the liquid level are achieved through interaction of all the parts; after detecting that the sampling device is in contact with the liquid level, the detection device transmits a signal to the power device to indicate the power device to stop or adjust the movement of the sampling device, so that the sampling device can accurately stay at a serum position to collect a sample.

Description

Technical Field

[0001] This invention belongs to the technical field of fluorescence immunoassay detection equipment, and in particular relates to a liquid level detection component for use in an analyzer. Background Technology

[0002] Sampling technology is a commonly used detection technique in biomedical testing. It utilizes the property that the analyte fluoresces when excited by light of a specific wavelength for qualitative and quantitative detection. Due to its advantages such as high sensitivity, strong specificity, fast detection speed, and safety and stability, sampling technology is widely used in clinical testing and has broad application prospects in areas such as endocrine disease detection, infectious disease detection, obstetric and gynecological disease detection, tumor marker detection, genetic disease detection, and blood and cytology testing.

[0003] The design of the liquid level detection component is particularly important for sampling technology. Chinese patent document CN102928041A discloses a small-volume liquid level detection device, including a quartz container. The quartz container has a circular cross-section, and pairs of straight inert electrodes are arranged inside it. Below the straight inert electrodes, pairs of curved inert electrodes are also arranged inside the quartz container. One end of the curved inert electrode is fixed to the inner wall of the quartz container, and the other end is bent downwards, with its end located at the center of the quartz container. Both the straight and curved inert electrodes are connected to a microcontroller sequentially through a receiving and conversion circuit and a comparison and amplification circuit. This microcontroller also controls the straight and curved inert electrodes separately through a driving circuit. This is a small-volume liquid level detection device with a simple structure, ingenious design, and reasonable layout, capable of automatically and accurately measuring the volume of organic reagents.

[0004] While the above technical solution can minimize inaccuracies in liquid level measurement caused by factors such as liquid viscosity and capillary effect, ensuring measurement accuracy and saving manpower and time, in practical use, when collecting serum samples with the sampling needle, since the serum is only in the upper layer of the sample tube, if the liquid level cannot be sensed and the sample is collected at a fixed height, plasma samples may be collected, thus affecting the results and potentially impacting the sampling and testing outcomes.

[0005] Therefore, it is necessary to develop a new liquid level detection component that allows the sampling needle to accurately stop at the serum position to collect samples, avoiding the collection of plasma samples. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a liquid level detection device that enables the sampling needle to accurately stop at the serum position to collect samples.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a liquid level detection component, including a mounting plate, the mounting plate being fixed on a base, a linear guide rail being provided on the mounting plate, a sampling device sliding up and down on the linear guide rail, a power device being fixed on the mounting plate, the power device providing power to the sampling device, characterized in that the sampling device is connected to a detection device, the detection device being used to detect the capacitance change generated when the sampling device comes into contact with the liquid surface, and the detection device controlling the up and down sliding of the sampling device.

[0008] The liquid level detection assembly achieves high-precision detection and automated control of the liquid level through the interaction of its various parts. The mounting plate provides structural support for the entire device, ensuring that all components are firmly fixed on a frame. The linear guide rail provides a precise movement path for the sampling device. The power unit is responsible for driving the sampling device to move up and down along the linear guide rail. After the detection device detects that the sampling device is in contact with the liquid surface, it sends a signal to the power unit, instructing it to stop or adjust the movement of the sampling device, so that the sampling device can accurately stop at the serum position to collect samples.

[0009] Preferably, the power device is a lead screw motor, which is connected to the lead screw via a coupling. A first bearing seat is provided below the coupling, and the lead screw is embedded in the first bearing seat. The end of the lead screw is located in the base, which serves as the second bearing seat for the lead screw.

[0010] As a power unit, the lead screw motor provides high-precision linear motion. It converts the rotational motion of the motor into linear motion, which can precisely control the up and down movement of the sampling device, enabling the liquid level detection component to maintain high precision and stability during fine adjustments and long stroke movements.

[0011] Preferably, the lead screw is provided with a threaded sleeve, and the sampling device is connected to the lead screw through the threaded sleeve. The sampling device includes a sampling needle slider, a sampling needle, a sampling needle drive block, and a sampling needle pressure plate. The threaded sleeve is nested inside the sampling needle slider. The surface of the sampling needle slider contacts the linear guide rail and slides up and down along the linear guide rail. The lower end face of the sampling needle slider is connected to the sampling needle drive block. The sampling needle is located inside the sampling needle drive block. The sampling needle pressure plate is fixed above the sampling needle drive block.

[0012] The threaded sleeve is mounted on the lead screw, and the rotational motion of the lead screw is converted into the linear motion of the sampling device through the threaded connection. The sampling needle slider is nested in the threaded sleeve and slides up and down along the linear guide under the drive of the lead screw to achieve precise positioning of the sampling needle. The sampling needle drive block is connected to the lower end face of the sampling needle slider and is the direct drive component of the sampling needle. It transmits the motion of the sampling needle slider to the sampling needle. The sampling needle pressure plate is fixed above the sampling needle drive block and plays the role of fixing and supporting the sampling needle to prevent the sampling needle from shifting or loosening during the movement.

[0013] Preferably, the sampling needle includes an inner needle, a sleeve, and a limiting block. The limiting block is engaged with the sampling needle drive block and the sampling needle pressure plate. The outer edge of the sleeve is in contact with the inner edge of the limiting block, and the inner needle is located inside the sleeve.

[0014] Preferably, the sampling needle tip structure generates a capacitance change when it comes into contact with the liquid surface.

[0015] Preferably, the sampling device is connected to the detection device, which can detect the capacitance change of the sampling needle. The detection device controls the up-and-down movement of the sampling needle slider by driving the lead screw connected to the lead screw motor to rotate.

[0016] The inner needle, located inside the cannula, is the part that directly contacts the liquid and is responsible for sample collection. The detection device is connected to the sampling device and is used to monitor the capacitance change of the sampling needle in real time. When the inner needle enters the liquid from the air, the detection device can immediately sense the capacitance change.

[0017] Preferably, the sampling device is connected to the mounting plate via a synchronization chain, which is a multi-link chain structure.

[0018] Preferably, the synchronization chain is fixed to the upper end of the mounting plate by a synchronization chain bracket, and the synchronization chain is connected to the sampling needle slider by a synchronization chain fixing plate.

[0019] The multi-section synchronous chain design ensures the stability of the sampling device during movement, enabling the sampling needle slider to move precisely up and down on the linear guide rail.

[0020] Preferably, an optical coupler is fixed on the mounting plate, and an optical coupler baffle is fixed on the sampling device.

[0021] The optocoupler and optocoupler stop are designed to provide precise position control and process safety, ensuring that the level detection component does not exceed its set range of motion. This guarantees the safe operation of the device and prevents overshoot and collisions during mechanical processes.

[0022] Preferably, the detection device includes a liquid level detection circuit structure, which includes a needle-capacitive signal input device, a phase detector, a loop filter, a voltage-controlled oscillator, and a signal output device, connected in series; a frequency divider is also connected between the voltage-controlled oscillator and the phase detector.

[0023] The voltage-controlled oscillator uses the input DC signal to control the oscillation frequency of the output signal, the phase detector is used to detect the phase difference between two input signals, and the loop filter is a low-pass filter that averages the DC signal with ripples output by the phase detector into a DC signal with less AC component.

[0024] Preferably, the pin-capacitive signal input device includes a square wave amplifier circuit, which includes resistors R1, R2, R3, and R4, and an operational amplifier U1. The positive input terminal of the operational amplifier U1 is connected to resistor R1; the negative input terminal of the operational amplifier U1 is connected to resistor R2; resistor R4 is connected between the positive input terminal and the output terminal of the operational amplifier U1; one end of resistor R3 is connected to the negative input terminal of the operational amplifier U1, and the other end is grounded.

[0025] Preferably, the voltage-controlled oscillator includes an LC oscillation circuit, which includes capacitor C1, capacitor C2, resistor R5, and inductor L1; capacitor C1 and resistor R5 are connected in series and then connected to the output terminal of the LC oscillation circuit, and capacitor C1 is also connected to the input terminal of the LC oscillation circuit.

[0026] The capacitor C2 and the inductor L1 are connected between the resistor R5 and the output terminal of the LC oscillation circuit, and both the capacitor C2 and the inductor L1 are grounded.

[0027] Preferably, the loop filter includes a rectifier filter circuit, which includes a resistor R7, an operational amplifier U2, an operational amplifier U3, and a capacitor C3; the input terminal of the rectifier filter circuit is connected in sequence to resistors R6, R8, R9, R10, and R11, and resistor R11 is connected to the output terminal of the rectifier filter circuit.

[0028] The positive input terminal of the operational amplifier U2 is connected between resistors R6 and R8, and the negative input terminal of the operational amplifier U2 is grounded; the anode of diode D2 is connected between resistors R8 and R9, and the cathode of diode D2 is connected to the output terminal of the operational amplifier U2 and the anode of diode D1, respectively; the cathode of diode D1 is connected to the positive input terminal of the operational amplifier U2.

[0029] One end of resistor R7 is connected to the input terminal of the rectifier filter circuit, and the other end is connected to the positive input terminal of operational amplifier U3; the negative input terminal of operational amplifier U3 is grounded; the output terminal of operational amplifier U3 is connected between resistor R10 and resistor R11.

[0030] One end of the inductor C3 is connected between the resistor R11 and the output terminal of the rectifier filter circuit, and the other end is grounded.

[0031] Preferably, the phase detector includes a comparison circuit, which includes an operational amplifier U4, a capacitor C4, and a resistor R12;

[0032] The positive input terminal of the operational amplifier U4 is connected to a signal, and the negative input terminal of the operational amplifier U4 is connected to the power supply VDD; one end of the resistor R12 is connected to the output terminal of the operational amplifier U4, and the other end is connected to the power supply VDD; one end of the capacitor C4 is connected to the output terminal of the operational amplifier U4, and the other end is grounded.

[0033] The liquid level detection circuit is designed to convert changes in needle capacitance into changes in voltage. After signal processing, it can accurately determine whether the sampling needle has touched the liquid surface, ensuring that the sampling needle accurately stops at the serum position to collect the sample and avoiding the collection of plasma samples. Attached Figure Description

[0034] The following detailed description, in conjunction with the accompanying drawings and embodiments of the present invention, is as follows:

[0035] Figure 1 This is a schematic diagram of the main structure of the liquid level detection component of the present invention. Figure 1 ;

[0036] Figure 2 This is a schematic diagram of the main structure of the liquid level detection component of the present invention. Figure 2 ;

[0037] Figure 3 yes Figure 1 Schematic diagram of the main structure of the power unit;

[0038] Figure 4 yes Figure 1 A schematic diagram of the main structure of the sampling device;

[0039] Figure 5 yes Figure 4 A schematic diagram of the main structure of the sampling needle;

[0040] Figure 6 yes Figure 4 A cross-sectional view of the structure after removing the sampling needle;

[0041] Figure 7This is a schematic diagram of the liquid level detection circuit structure of the present invention;

[0042] Figure 8 This is a diagram of the square wave amplifier circuit in the liquid level detection circuit structure of the present invention;

[0043] Figure 9 This is a diagram of the LC oscillation circuit in the liquid level detection circuit structure of the present invention;

[0044] Figure 10 This is a diagram of the rectifier and filter circuit in the liquid level detection circuit structure of the present invention;

[0045] Figure 11 This is a comparison circuit diagram in the liquid level detection circuit structure of the present invention;

[0046] Figure 12 This is a flowchart illustrating the method of using the liquid level detection component of the present invention;

[0047] The components are as follows: 1-Mounting plate, 2-Base, 3-Linear guide rail, 4-Detection device, 5-Screw motor, 6-Coupling, 7-Screw, 8-First bearing seat, 9-Threaded sleeve, 10-Sampling needle slider, 11-Sampling needle, 12-Sampling needle drive block, 13-Sampling needle pressure plate, 14-Inner needle, 15-Sleeve, 16-Limiting block, 17-Synchronous chain, 18-Synchronous chain bracket, 19-Synchronous chain fixing plate, 20-Optical coupler, 21-Optical coupler baffle, 22-Buffer zone, 23-Pin capacitor signal input device, 24-Phase detector, 25-Loop filter, 26-Voltage controlled oscillator, 27-Signal output device, 28-Frequency divider. Detailed Implementation

[0048] As attached Figures 1-12 As shown, the liquid level detection component of this embodiment includes a mounting plate 1, which is fixed on a base 2. A linear guide rail 3 is provided on the mounting plate 1, and the sampling device slides up and down on the linear guide rail 3. A power device is fixed on the mounting plate 1, and the power device provides power to the sampling device. The sampling device is characterized in that a detection device 4 is connected to it. The detection device 4 is used to detect the capacitance change generated when the sampling device comes into contact with the liquid surface, and the detection device 4 controls the up and down sliding of the sampling device.

[0049] Specifically, such as Figure 1-3 As shown, the power device is a lead screw motor 5, which is connected to a lead screw 7 via a coupling 6. A first bearing seat 8 is provided below the coupling 6, and the lead screw 7 is embedded in the first bearing seat 8. The end of the lead screw 7 is located in the base 2, which serves as the second bearing seat for the lead screw 7. The lead screw 7 converts the rotational motion of the motor into linear motion, which can precisely control the up and down movement of the sampling device.

[0050] A threaded sleeve 9 is provided on the lead screw 7. The sampling device is connected to the lead screw 7 through the threaded sleeve 9. The sampling device includes a sampling needle slider 10, a sampling needle 11, a sampling needle drive block 12, and a sampling needle pressure plate 13. The threaded sleeve 9 is nested inside the sampling needle slider 10. The surface of the sampling needle slider 10 is in contact with the linear guide rail 3 and slides up and down along the linear guide rail 3. The sampling needle drive block 12 is connected to the lower end face of the sampling needle slider 10. The sampling needle 11 is located inside the sampling needle drive block 12. The sampling needle pressure plate 13 is fixed above the sampling needle drive block 12.

[0051] It should be noted that during operation, the threaded sleeve 9, through its threaded engagement with the lead screw 7, converts the rotational motion of the lead screw 7 into the linear motion of the sampling device. The sampling needle slider 10 is nested on the threaded sleeve 9 and, driven by the lead screw 7, slides up and down along the linear guide rail 3 to achieve precise positioning of the sampling needle 11. The base 2, as the second bearing seat of the lead screw 7, works in conjunction with the first bearing seat 8 to connect the lead screw 7 and the lead screw motor 5 to transmit power or adjust the position.

[0052] like Figure 4 , Figure 5 As shown, the sampling needle 11 includes an inner needle 14, a sleeve 15 and a limiting block 16. The limiting block 16 is snapped into the inside of the sampling needle drive block 12 and the sampling needle pressure plate 13. The outer edge of the sleeve 15 is in contact with the inner edge of the limiting block 16.

[0053] Specifically, such as Figure 6 As shown, the structure of the limiting block 16 is matched with the internal structure of the sampling needle drive block 12 and the sampling needle pressure plate 13, and is tightly engaged. In addition, the limiting block 16 is also provided with a buffer zone 22 to absorb the over-rush force of the sampling needle 11 during mechanical operation, so as to avoid damage to the sampling needle 11 or the sample due to excessive operation.

[0054] The inner needle 14 is located inside the sleeve 15. When the tip structure of the sampling needle 11 changes from contact with air to contact with the liquid surface, a capacitance change occurs. The sampling device is connected to a detection device 4, which can detect the capacitance change of the sampling needle 11. The detection device 4 controls the up and down movement of the sampling needle slider 10 by rotating the lead screw 7 connected to the drive lead screw motor 5.

[0055] The inner needle 14 is the part that comes into direct contact with the liquid and is responsible for sample collection. The detection device 4 is connected to the sampling device and is used to monitor the capacitance change of the sampling needle in real time. When the inner needle 14 enters the liquid from the air, the detection device 4 can immediately sense the capacitance change.

[0056] It should be noted that the circuit principle of this capacitance change is as follows: when the inner needle 14 changes from contact with air to contact with the liquid surface, a capacitance change will be generated. The liquid surface detection circuit converts the needle capacitance change into a voltage change. After signal processing and judgment, it can be determined whether the inner needle 14 has touched the liquid surface.

[0057] Specifically, such as Figure 7 As shown, the detection device 4 includes a liquid level detection circuit structure, which includes a needle-capacitive signal input device 23, a phase detector 24, a loop filter 25, a voltage-controlled oscillator 26, and a signal output device 27, connected in series. A frequency divider 28 is also connected between the voltage-controlled oscillator 26 and the phase detector 24. The arrows in the figure indicate the direction of signal transmission. The core of this circuit is a closed-loop structure.

[0058] The pin-capacitive signal input device 2 includes a square wave amplifier circuit, specifically as follows: Figure 8 As shown, the square wave amplifier circuit includes resistors R1, R2, R3, and R4, and an operational amplifier U1. The positive input terminal of the operational amplifier U1 is connected to resistor R1.

[0059] The negative input terminal of the operational amplifier U1 is connected to the resistor R2; the positive input terminal of the operational amplifier U1 is connected to the output terminal of the operational amplifier U1 by the resistor R4; one end of the resistor R3 is connected to the negative input terminal of the operational amplifier U1, and the other end is grounded.

[0060] The square wave amplifier circuit uses a crystal oscillator to output two 1MHz square waves with the same amplitude and opposite phase. The operational amplifier circuit U1 then differentially amplifies the two square waves to increase the load-carrying capacity.

[0061] The voltage-controlled oscillator 26 includes an LC oscillation circuit, specifically as follows: Figure 9 As shown, the LC oscillation circuit includes capacitor C1, capacitor C2, resistor R5, and inductor L1; capacitor C1 and resistor R5 are connected in series and then connected to the output terminal of the LC oscillation circuit, and capacitor C1 is also connected to the input terminal of the LC oscillation circuit.

[0062] A capacitor C2 and an inductor L1 are connected between the resistor R5 and the output terminal of the LC oscillation circuit, and both the capacitor C2 and the inductor L1 are grounded.

[0063] The LC oscillation circuit, after the amplified square wave is isolated by capacitor C1 and current limited by resistor R5, drives the LC oscillation circuit composed of capacitor C2 of the sampling needle and fixed inductor L1. When the capacitance C2 of the sampling needle changes, the amplitude and phase of the sinusoidal signal passing through the LC oscillation circuit will change.

[0064] The loop filter 25 includes a rectifier and filter circuit, specifically as follows: Figure 10As shown, the rectifier and filter circuit includes a resistor R7, an operational amplifier U2, an operational amplifier U3, and a capacitor C3; the input terminal of the rectifier and filter circuit is connected in sequence to resistors R6, R8, R9, R10, and R11, and resistor R11 is connected to the output terminal of the rectifier and filter circuit.

[0065] The positive input terminal of the operational amplifier U2 is connected between resistors R6 and R8, and the negative input terminal of the operational amplifier U2 is grounded; the anode of diode D2 is connected between resistors R8 and R9, and the cathode of diode D2 is connected to the output terminal of the operational amplifier U2 and the anode of diode D1, respectively; the cathode of diode D1 is connected to the positive input terminal of the operational amplifier U2.

[0066] One end of resistor R7 is connected to the input terminal of the rectifier filter circuit, and the other end is connected to the positive input terminal of operational amplifier U3; the negative input terminal of operational amplifier U3 is grounded; the output terminal of operational amplifier U3 is connected between resistor R10 and resistor R11.

[0067] One end of the inductor C3 is connected between the resistor R11 and the output terminal of the rectifier filter circuit, and the other end is grounded.

[0068] The rectifier and filter circuit rectifies the waveform signal after LC oscillation through a rectifier circuit composed of operational amplifiers U2 and U3, concentrating the full-cycle signal into the positive half-cycle. Then, it is filtered by an RC filter circuit composed of resistor R11 and inductor C3 to obtain a stable DC signal.

[0069] The phase detector 24 includes a comparison circuit, specifically as follows: Figure 11 As shown, the comparison circuit includes an operational amplifier U4, a capacitor C4, and a resistor R12;

[0070] The positive input terminal of the operational amplifier U4 is connected to a signal, and the negative input terminal of the operational amplifier U4 is connected to the power supply VDD; one end of the resistor R12 is connected to the output terminal of the operational amplifier U4, and the other end is connected to the power supply VDD; one end of the capacitor C4 is connected to the output terminal of the operational amplifier U4, and the other end is grounded.

[0071] The comparison circuit compares the filtered DC signal with a reference voltage. If the sampling needle does not touch the liquid, that is, the sampling needle capacitance C2 does not change, the voltage after RC filtering is higher than the reference value, and the comparator outputs a high level. If the sampling needle touches the liquid, that is, the sampling needle capacitance C2 does not change, the voltage after RC filtering is lower than the reference value, and the comparator outputs a low level.

[0072] like Figure 1 , Figure 2 As shown, the sampling device is connected to the mounting plate 1 via a synchronization chain 17. The synchronization chain 17 is a multi-link chain structure. The synchronization chain 17 is fixed to the upper end of the mounting plate 1 via a synchronization chain bracket 18. The synchronization chain 17 is connected to the sampling needle slider 10 via a synchronization chain fixing plate 19. An optocoupler 20 is fixed on the mounting plate 1, and an optocoupler baffle 21 is fixed on the sampling device.

[0073] It should be noted that as the sampling device moves, the optical coupler baffle 21 also moves. When the optical coupler baffle 21 enters the light path of the optical coupler 20, it will change the state of the optical coupler 20. After the electronic control system detects the change in the state of the optical coupler 20, the system will immediately issue a command to control the lead screw motor 5 to stop moving, thereby precisely controlling the position of the sampling device to ensure that it does not exceed the set movement range.

[0074] like Figure 12 As shown, the liquid level detection component of the present invention includes a normal detection process, which includes the following steps:

[0075] S1: Move the sampling needle 11 directly above the sample tube, and lower the sampling needle 11 so that the sampling needle 11 is inserted into the sample tube;

[0076] S2: Determine whether the sampling needle 11 is in contact with the liquid surface of the sample tube by measuring the capacitance change of the sampling needle 11. If it is not in contact with the liquid surface, return to S1; if it is in contact with the liquid surface, continue to S3.

[0077] S3: The detection device 4 sends a signal to the power device, instructing it to immediately stop the movement of the sampling device, so that the sampling needle 11 just stops at the liquid surface;

[0078] S4: The detection device 4 sends a signal to the power device, instructing it to control the sampling needle 11 to continue descending to the specified sampling height and accurately stop at the serum position;

[0079] S5: After the sampling needle 11 is precisely positioned at the serum location, sample collection is performed.

[0080] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A liquid level detection assembly, comprising a mounting plate fixed to a base, a linear guide rail provided on the mounting plate, a sampling device sliding up and down on the linear guide rail, and a power device fixed on the mounting plate, the power device providing power to the sampling device, characterized in that... The sampling device is connected to a detection device, which is used to detect the capacitance change generated when the sampling device comes into contact with the liquid surface, and the detection device controls the up and down sliding of the sampling device.

2. The liquid level detection component according to claim 1, characterized in that, The power unit is a lead screw motor, which is connected to the lead screw via a coupling. A first bearing seat is provided below the coupling, and the lead screw is embedded in the first bearing seat. The end of the lead screw is located in the base, which serves as the second bearing seat for the lead screw.

3. The liquid level detection component according to claim 2, characterized in that, A threaded sleeve is provided on the lead screw, and the sampling device is connected to the lead screw through the threaded sleeve. The sampling device includes a sampling needle slider, a sampling needle, a sampling needle drive block, and a sampling needle pressure plate. The threaded sleeve is nested inside the sampling needle slider. The surface of the sampling needle slider contacts the linear guide rail and slides up and down along the linear guide rail. The sampling needle drive block is connected to the lower end face of the sampling needle slider. The sampling needle is located inside the sampling needle drive block. The sampling needle pressure plate is fixed above the sampling needle drive block.

4. The liquid level detection component according to claim 3, characterized in that, The sampling needle includes an inner needle, a sleeve, and a limiting block. The limiting block is engaged with the sampling needle drive block and the sampling needle pressure plate. The outer edge of the sleeve is in contact with the inner edge of the limiting block, and the inner needle is located inside the sleeve.

5. The liquid level detection component according to claim 4, characterized in that, When the tip of the sampling needle comes into contact with the liquid surface, a change in capacitance occurs.

6. The liquid level detection component according to claim 5, characterized in that, The sampling device is connected to the detection device, which can detect the capacitance change of the sampling needle. The detection device controls the up-and-down movement of the sampling needle slider by driving the lead screw connected to the lead screw motor to rotate.

7. The liquid level detection component according to claim 1, characterized in that, The sampling device is connected to the mounting plate via a synchronization chain, which is a multi-link chain structure.

8. The liquid level detection component according to claim 7, characterized in that, The synchronization chain is fixed to the upper end of the mounting plate by a synchronization chain bracket, and the synchronization chain is connected to the sampling needle slider by a synchronization chain fixing plate.

9. The liquid level detection component according to claim 1, characterized in that, An optical coupler is fixed on the mounting plate, and an optical coupler baffle is fixed on the sampling device.

10. The liquid level detection component according to claim 1, characterized in that, The detection device includes a liquid level detection circuit structure, which includes a needle-capacitive signal input device, a phase detector, a loop filter, a voltage-controlled oscillator, and a signal output device, connected in series. A frequency divider is also connected between the voltage-controlled oscillator and the phase detector.

11. The liquid level detection component according to claim 10, characterized in that, The pin-capacitive signal input device includes a square wave amplifier circuit, which includes resistors R1, R2, R3, and R4, and an operational amplifier U1. The positive input terminal of the operational amplifier U1 is connected to resistor R1; the negative input terminal of the operational amplifier U1 is connected to resistor R2; resistor R4 is connected between the positive input terminal and the output terminal of the operational amplifier U1; one end of resistor R3 is connected to the negative input terminal of the operational amplifier U1, and the other end is grounded.

12. The liquid level detection component according to claim 10, characterized in that, The voltage-controlled oscillator includes an LC oscillation circuit, which includes capacitor C1, capacitor C2, resistor R5, and inductor L1; capacitor C1 and resistor R5 are connected in series and then connected to the output terminal of the LC oscillation circuit, and capacitor C1 is also connected to the input terminal of the LC oscillation circuit. The capacitor C2 and the inductor L1 are connected between the resistor R5 and the output terminal of the LC oscillation circuit, and both the capacitor C2 and the inductor L1 are grounded.

13. The liquid level detection component according to claim 10, characterized in that, The loop filter includes a rectifier filter circuit, which includes a resistor R7, an operational amplifier U2, an operational amplifier U3, and a capacitor C3. The input terminal of the rectifier filter circuit is connected in sequence to resistors R6, R8, R9, R10, and R11, and resistor R11 is connected to the output terminal of the rectifier filter circuit. The positive input terminal of the operational amplifier U2 is connected between resistors R6 and R8, and the negative input terminal of the operational amplifier U2 is grounded; the anode of diode D2 is connected between resistors R8 and R9, and the cathode of diode D2 is connected to the output terminal of the operational amplifier U2 and the anode of diode D1, respectively; the cathode of diode D1 is connected to the positive input terminal of the operational amplifier U2. One end of resistor R7 is connected to the input terminal of the rectifier filter circuit, and the other end is connected to the positive input terminal of operational amplifier U3; the negative input terminal of operational amplifier U3 is grounded; the output terminal of operational amplifier U3 is connected between resistor R10 and resistor R11. One end of the inductor C3 is connected between the resistor R11 and the output terminal of the rectifier filter circuit, and the other end is grounded.

14. The liquid level detection component according to claim 10, characterized in that, The phase detector includes a comparison circuit, which includes an operational amplifier U4, a capacitor C4, and a resistor R12. The positive input terminal of the operational amplifier U4 is connected to a signal, and the negative input terminal of the operational amplifier U4 is connected to the power supply VDD; one end of the resistor R12 is connected to the output terminal of the operational amplifier U4, and the other end is connected to the power supply VDD; one end of the capacitor C4 is connected to the output terminal of the operational amplifier U4, and the other end is grounded.

Images