Digital display ultrasonic liquid level sensor and threshold setting method

Abstract

The invention discloses a digital display ultrasonic liquid level sensor and a threshold setting method, and relates to the technical field of sensors, and the digital display ultrasonic liquid level sensor comprises a shell, an ultrasonic probe, a control circuit unit, a key unit, a display unit and an output unit. The core of the method is that a unique echo signal detection algorithm is adopted, the wave starting position, the wave crest position and the wave ending position of a transmitted signal wave are positioned firstly, then echoes are detected and received from the wave crest position to identify superposed waves, and detection blind areas are effectively reduced. One-key setting and fine adjustment of a threshold value can be realized through the keys, the display screen displays measurement data, the threshold value, signal intensity and the like in real time, independent work can be realized without external equipment, system complexity and maintenance difficulty are reduced, and installation and debugging convenience and measurement precision are improved.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a digital display ultrasonic liquid level sensor and a threshold setting method. Background Art

[0002] Currently, conventional threshold setting methods require dedicated signal wiring and must be used in conjunction with a host computer or controller. This results in weak independent sensor functionality, increasing system complexity and overall cost. Furthermore, existing sensors lack intuitive display of measurement data and parameters, hindering user interaction when adjusting parameters. Troubleshooting requires reliance on additional testing equipment, significantly increasing maintenance complexity.

[0003] Furthermore, the ultrasonic sensor's mounting angle plays a crucial role in measurement accuracy, anti-interference capabilities, and system reliability. However, existing solutions typically only output a raw distance signal and fail to provide key auxiliary information such as signal strength and device operating status, significantly complicating installation and commissioning. Furthermore, traditional sensors' echo signal processing methods suffer from a large detection blind spot, impacting the accuracy of short-range or close-range level measurements and making it difficult to meet the demands of high-precision applications.

[0004] These defects limit the application of ultrasonic liquid level sensors in independent systems, rapid debugging and high-precision measurement scenarios. There is an urgent need for an improved solution that can solve the above problems. Summary of the Invention

[0005] In order to solve the technical problems existing in the background technology, the present invention proposes a digital display ultrasonic liquid level sensor.

[0006] In the first aspect, the present invention proposes a digital ultrasonic liquid level sensor, comprising a first shell and a second shell, and also comprising a control circuit unit, an ultrasonic probe, a button unit, a display unit, an indication unit, and an output unit built into the first shell and the second shell. The control circuit unit is electrically connected to the ultrasonic probe, the button unit, the display unit, the indication unit, and the output unit, respectively. The button unit is used to realize one-button setting of thresholds and parameter adjustment. The display unit is used to display measurement data, threshold parameters, and operating status information in real time. Threshold setting and data viewing can be independently completed without relying on external debugging tools.

[0007] Furthermore, the button unit includes two independent buttons, namely a SET button and a MODE button; the SET button is used to set the upper threshold value and enter the upper limit value adjustment menu, and the MODE button is used to set the lower threshold value and enter the lower limit value adjustment menu.

[0008] Furthermore, the display unit is an OLED display screen, which can display the distance value, upper threshold, lower threshold, output status and received signal strength of the real-time detection target, and the numerical unit is mm.

[0009] Furthermore, the control circuit unit includes a power supply circuit, an ultrasonic excitation circuit, an ultrasonic receiving circuit, a key detection circuit, a display screen driving circuit, a temperature detection circuit, an indicator light and a signal output circuit.

[0010] Furthermore, the signal output circuit is connected to an output unit, and the output unit supports three output signals: upper threshold switching value, lower threshold switching value and threshold interval analog value.

[0011] Furthermore, the digital ultrasonic liquid level sensor further includes an echo signal detection algorithm, which includes: Step 1: Locate the start position, peak position and end position of the transmitted signal wave; Step 2: Detect the received echo signal starting from the peak position of the transmitted signal wave to identify the superimposed echo and reduce the detection blind area.

[0012] Furthermore, the display unit also displays the current output status on the main function interface, wherein a solid circle indicates that the corresponding threshold signal output is 1, and a hollow circle indicates that the corresponding threshold signal output is 0.

[0013] Furthermore, the indicating unit is configured as a status indicator light, which is always on when there is no target object within the measuring range, and flashes when there is a target object within the measuring range.

[0014] Furthermore, the digital ultrasonic liquid level sensor has an automatic key lock function: it automatically locks the key when no operation exceeds 5 minutes; in the key lock state, long press the combination of the SET key and the MODE key for more than 1 second to unlock the key.

[0015] In the second aspect, the present invention proposes a threshold setting method for a digital ultrasonic liquid level sensor, including: when the detection target is at the threshold position to be set, long press the SET key for more than 2 seconds to set the upper threshold with one click, or long press the MODE key for more than 2 seconds to set the lower threshold with one click. After the setting is completed, the display unit synchronously updates and displays the set threshold.

[0016] Furthermore, the threshold setting method further includes: setting a hysteresis value, and when the target liquid level fluctuates around the set threshold, the hysteresis value is used to maintain the stability of the signal output state.

[0017] Beneficial effects of the present invention: Accurately identifying echo signals is achieved through a two-step process: the first step precisely locates the start, peak, and end positions of the transmitted signal wave; the second step detects the received echo signal starting from the peak of the transmitted signal wave. This effectively identifies the superimposed wave formed by the transmitted wave and the echo, significantly reducing the product's detection blind spots. This improvement significantly improves the sensor's measurement accuracy in short-range or close-range measurement scenarios, while reducing measurement errors caused by blind spots and enhancing anti-interference capabilities in complex environments. This facilitates installation and commissioning, indirectly improving system reliability. In addition, the algorithm's precise processing of echo signals enables the sensor to stably output auxiliary information such as signal strength, further assisting users in determining whether the installation direction angle is reasonable, optimizing the installation and debugging process and reducing debugging difficulties caused by signal processing problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the split structure of the present invention; Figure 2 It is a schematic diagram of the assembly structure of the present invention; Figure 3 A half-section view of the present invention after assembly; Figure 4 It is a schematic diagram of the structural connection of the present invention; Figure 5 is a functional block diagram of the present invention; Figure 6 This is an algorithm flow chart of step 1 in the present invention; Figure 7 This is the algorithm flow chart of step 2 in the present invention; Figure 8 This is a diagram showing the operation effect of the algorithm in the present invention; Figure 9 This is a structural block diagram of the present invention entering the expert menu through the setting interface; Figure 10 A schematic diagram showing that the hysteresis value of the present invention limits the hysteresis of signal transitions near a threshold value; Figure 11 This is a schematic diagram of the interface for entering the debugging mode of the present invention; Figure 12 This is a schematic diagram of the interface when the target exceeds the measuring range or the angle deviation of the target plane is too large in the present invention.

[0019] In the figure: 1. first shell; 2. second shell; 3. control circuit unit; 4. ultrasonic probe; 5. key unit; 6. display unit; 7. indication unit; 8. output unit; 9. key cap; 10. transparent window. DETAILED DESCRIPTION

[0020] Reference Figure 1-8 The digital ultrasonic liquid level sensor proposed in this invention realizes independent operation, intuitive display and high-precision liquid level detection functions through integrated structural design and coordinated cooperation of various components. The specific technical solution is as follows: The digital ultrasonic liquid level sensor includes a first housing 1 made of metal, a second housing 2 made of nickel-plated copper sleeve, a control circuit board with a built-in control circuit unit 3, an ultrasonic probe 4, two independent buttons of a key unit 5, including a SET button and a MODE button, a display unit 6 with an OLED display, an indication unit 7 with a status indicator, an output unit 8 with a wire, two keycaps 9 corresponding to the SET button and the MODE button, and two transparent windows 10 corresponding to the status indicator and the OLED display. The control circuit unit 3 integrates multiple circuit modules with different functions but closely coordinated. Among them, the power supply circuit is responsible for providing stable and reliable power support for the entire sensor system, ensuring that each component can operate stably under normal operating voltage. For example, it provides sufficient driving voltage for the ultrasonic excitation circuit and provides appropriate operating voltage for the display driver circuit. The ultrasonic excitation circuit can generate an electrical signal with a specific frequency and intensity based on the control logic. This signal is applied to the ultrasonic probe, prompting the probe to emit an ultrasonic pulse. In different application scenarios, the frequency and intensity of the ultrasonic excitation circuit's output signal need to be flexibly adjusted according to the required measurement distance and accuracy. For example, when measuring the liquid level of a large water storage tank at a long distance, it may be necessary to increase the intensity of the excitation signal to ensure that the ultrasonic wave can propagate far enough and obtain a clear reflected signal. The ultrasonic receiving circuit is dedicated to receiving the weak electrical signals transmitted by the ultrasonic probe and performing a series of processing on them, including amplification, filtering, and other operations. The amplifier circuit amplifies the weak electrical signal to an appropriate amplitude so that the subsequent circuit can accurately analyze and process it; the filtering circuit can effectively remove various noise interferences mixed in the signal, improving the purity and stability of the signal. For example, in some industrial environments, there is a lot of electromagnetic interference. The filtering function of the ultrasonic receiving circuit is particularly important. It can ensure that the received reflected signal is not affected by external interference, thereby ensuring the accuracy of the measurement results. The key detection circuit monitors the operating status of the key unit (SET key and MODE key) in real time. When the user presses a key, the key detection circuit can quickly capture the electrical signal changes generated by the key action and transmit this information to the core processor of the control circuit unit so that the corresponding functional instructions can be executed, such as threshold setting, parameter adjustment, etc. The display driver circuit is responsible for efficient data transmission and drive control with the display unit (OLED display). It transmits various data information processed by the control circuit unit, such as the detection target distance value, upper and lower thresholds, output status, and received signal strength, to the OLED display in an appropriate format and timing, and drives the display to display clearly and accurately, providing intuitive information feedback to the user. The temperature detection circuit has a built-in high-precision temperature sensor that can monitor temperature changes in the sensor's environment in real time. Because the propagation speed of ultrasound in air is significantly affected by temperature, the temperature detection circuit transmits the real-time collected temperature data to the control circuit unit. The control circuit unit accurately corrects the ultrasonic propagation speed based on a pre-set temperature compensation algorithm, thereby effectively improving the accuracy of liquid level measurement. For example, in outdoor oil tank level monitoring scenarios where temperature fluctuations are large, the temperature detection circuit and corresponding temperature compensation algorithm can ensure that the sensor can provide accurate liquid level measurement results under different temperature conditions; The indicator light and signal output circuit is responsible for controlling the on / off state of the status indicator light, providing intuitive feedback to the user on the sensor's operating status through the different states of the status indicator light (steady on or flashing). On the other hand, this circuit also assumes the task of controlling the signal output of the output unit. Based on the judgment results of the control circuit unit, it outputs signals such as the upper threshold switching value, lower threshold switching value, and threshold range analog value (4mA~20mA) that meet the requirements, so as to achieve effective data exchange and system integration with external devices. The display unit 6 is connected to the control circuit unit 3 via a dedicated interface circuit and can display a variety of key information in real time with high definition and high contrast. When displaying the real-time detection target distance value, it uses clear and easy-to-read digital fonts with millimeter accuracy to provide users with accurate liquid level information. For example, in chemical reactor liquid level monitoring, operators can clearly see the real-time value of the liquid level on the display screen, so that they can adjust production process parameters in a timely manner. The upper and lower threshold values ​​are also displayed in digital form and are distinguished from the real-time distance value, making it easy for users to view and compare them at any time. At the same time, the display can also display the output status in an intuitive graphical manner, such as using solid circles and hollow circles to represent the corresponding threshold signal outputs of 1 and 0, respectively, so that users can understand the current output status of the sensor at a glance. In addition, the display can also display the received signal strength information in the form of a bar graph or percentage to help users judge the working performance and signal quality of the sensor. For example, when the signal strength is weak, users can promptly check the installation location of the sensor or whether there are interference factors in the surrounding environment; The SET and MODE keys of the key unit 5 are connected to the key detection circuit of the control circuit unit 3 via independent circuits. These two keys are designed to cooperate with each other in terms of function, providing users with a convenient operation method. For example, when setting the threshold, the user only needs to long press the SET key. After the key detection circuit detects the long press action, it transmits a signal to the control circuit unit 3. The control circuit unit 3 then activates the upper threshold setting function, sets the currently detected target object distance value as the upper threshold, and updates the upper threshold display on the OLED display through the display driver circuit. Similarly, long pressing the MODE key can realize the one-key setting function of the lower threshold; When performing operations such as fine-tuning the threshold or entering the function menu, the user briefly presses a button, and the button detection circuit transmits the corresponding short-press signal to the control circuit unit 3. The control circuit unit 3 then executes the corresponding function according to the preset operation logic. For example, in the main function interface, if the SET button is briefly pressed, the control circuit unit 3 will recognize this operation and guide the user to the upper limit adjustment menu. The user can fine-tune the value by ±1 by briefly pressing the SET button again, and a long press can continuously increase or decrease the value. The data changes during the operation are displayed in real time on the OLED display, providing the user with clear operation feedback; The output unit 8 is closely connected to the indicator light and signal output circuit of the control circuit unit 3, and supports multiple types of signal outputs to meet the needs of different application scenarios and external devices. The upper threshold switch quantity and the lower threshold switch quantity output can provide a simple and direct switch signal for the external control system, which is used to trigger the alarm device, control the start and stop of the pump, and other operations. For example, in the liquid level control system of a sewage treatment plant, when the liquid level exceeds the upper threshold, the upper threshold switch quantity outputs a high-level signal, triggering the alarm device to remind the staff to deal with it in time; when the liquid level is lower than the lower threshold, the lower threshold switch quantity outputs a low-level signal to control the pump to stop working and avoid the occurrence of dry pumping; The threshold range analog output (4mA-20mA) is suitable for applications requiring a continuous and accurate liquid level signal. This analog signal can be seamlessly integrated with external PLC systems, data acquisition modules, and other equipment to achieve remote monitoring and precise control of liquid levels. For example, in a petrochemical tank level monitoring system, by connecting the sensor's analog output signal to the PLC system, the PLC system can accurately control the tank's feed and discharge valves based on real-time changes in the liquid level, ensuring that the tank level always remains within a safe and reasonable range. 1) Liquid level detection and data processing The ultrasonic excitation circuit in control circuit unit 3 sends an excitation signal to ultrasonic probe 4, driving the probe to emit an ultrasonic pulse. When the pulse hits the target and reflects, the probe receives the echo and transmits it to the ultrasonic receiving circuit in the control circuit unit. The control circuit unit calculates the distance to the target based on the sound wave's time of flight (ToF) and transmits this data to the display unit for real-time display. Simultaneously, control circuit unit 3 uses an echo signal detection algorithm (as shown in Figures 4 and 5) to locate the start, peak, and end of the transmitted signal wave. It then detects echoes starting at the peak, effectively identifying superimposed waves (as shown in the green area in Figure 6) and reducing detection blind spots.

[0021] The process of liquid level detection and data processing begins with the ultrasonic excitation circuit of the control circuit unit. The control circuit unit periodically sends a trigger signal to the ultrasonic excitation circuit according to the preset measurement cycle. After receiving the trigger signal, the ultrasonic excitation circuit quickly converts the low-voltage electrical signal into a high-frequency pulse electrical signal. The frequency of the high-frequency pulse electrical signal is usually between 20kHz and 5MHz, and the specific frequency is selected according to the actual measurement range. Generally speaking, for small-scale measurements, a higher frequency is selected to obtain higher accuracy; for large-scale measurements, a lower frequency is selected to ensure that the ultrasonic wave can propagate to a sufficiently long distance. After a high-frequency pulse electrical signal is applied to the ultrasonic probe, the ultrasonic probe uses the piezoelectric effect of the piezoelectric ceramic material to convert the electrical signal into mechanical vibration, thereby emitting an ultrasonic pulse in the direction of the detection target. The ultrasonic pulse propagates in the air at a certain beam angle, and its propagation speed is affected by factors such as ambient temperature, humidity, and air pressure. In order to eliminate the influence of temperature on the propagation speed of ultrasonic waves, the temperature detection circuit of the control circuit unit collects ambient temperature data in real time and transmits it to the core processor of the control circuit unit. The core processor accurately corrects the propagation speed of ultrasonic waves based on the pre-stored correspondence between temperature and sound speed; When an ultrasonic pulse encounters a target (such as a liquid surface), most of the ultrasonic wave is reflected back due to the large difference in acoustic impedance between liquid and air, forming a reflected echo. After transmitting the ultrasonic pulse, the ultrasonic probe quickly switches to receiving mode, receives the reflected echo, and converts it into a weak electrical signal to transmit to the ultrasonic receiving circuit of the control circuit unit. The ultrasonic receiving circuit first pre-amplifies the received weak electrical signal, raising the signal amplitude to an appropriate level for subsequent circuit processing. The amplified signal is then filtered through a bandpass filter to remove any noise interference and retain only the useful signal with a frequency close to that of the ultrasonic echo signal. The filtered signal is then transmitted to the core processor of the control circuit unit. The core processor records the time difference (Δt) between ultrasonic emission and reception, and calculates the vertical distance (h) from the ultrasonic probe to the target surface using the formula "Distance = Speed ​​of Sound (v) × Time Difference (Δt) / 2." Since the fixed distance (H) from the ultrasonic probe to the bottom of the container is already known during sensor installation, the actual liquid level = Hh. The core processor transmits this calculated liquid level data, along with other relevant information such as received signal strength, to the OLED display via the display driver circuit for real-time display. It can also output this liquid level data to external devices as analog or digital signals via indicator lights and signal output circuits, as needed. To further improve the accuracy of liquid level detection, this sensor uses a unique echo signal detection algorithm. This algorithm first locates the start, peak, and end positions of the transmitted signal wave through precise analysis of the transmitted signal wave. Then, it detects the received echo signal starting from the peak position of the transmitted signal wave. This can effectively identify the superposition signal of the transmitted wave and the echo, reducing the detection blind spot. For example, in some scenarios where the liquid level changes frequently and there are interference signals, this echo signal detection algorithm can accurately extract the effective echo signal from the complex signal, thereby improving the accuracy and stability of liquid level measurement. 2) Threshold setting and parameter adjustment When the user needs to set a threshold, first adjust the detection target to the position where the threshold is desired. For example, in an industrial water tank level control system, the user wants to set the upper limit of the water tank level to a specific height. At this time, the water tank level is adjusted to that height. Then, the user long-presses the SET key. When the SET key in the key unit is pressed, the internal contacts close, generating an electrical signal change. This electrical signal change is transmitted to the key detection circuit in the control circuit unit via a line connected to the key detection circuit. After the key detection circuit detects the long press of the SET key (usually a long press lasting more than 2 seconds is considered a valid long press), it transmits this information to the core processor of the control circuit unit. After receiving the command of long pressing the SET key, the core processor immediately starts the upper threshold setting function. It reads the distance value of the target object detected by the ultrasonic probe at this time and stores this distance value as the upper threshold. At the same time, the core processor sends an update command to the OLED display through the display driver circuit. The OLED display then updates the display content and displays the newly set upper threshold in clear digital form. In order to let the user intuitively understand that the threshold setting operation has been completed, the control circuit unit will also control the status indicator to flash a certain number of times, for example, flashing 3 times, to prompt the user that the operation is successful; Similarly, when the user long-presses the MODE button, the button detection circuit detects the long-press action of the MODE button and transmits it to the core processor. The core processor activates the lower threshold setting function, reads the currently detected target distance value and stores it as the lower threshold, updates the lower threshold display on the OLED display, and controls the status indicator to flash to inform the user that the lower threshold setting is successful; In the main function interface, the user briefly presses the SET button. The button detection circuit detects the short press of the SET button (usually a short press of less than 2 seconds is recognized as a short press) and transmits a signal to the core processor of the control circuit unit. After the core processor recognizes this action, it guides the user to the upper limit adjustment menu. At this time, the display content of the OLED display switches to the upper limit adjustment interface, showing the current upper limit threshold value and prompting the user to make fine adjustments on the screen. The user short presses the SET button again, and after the core processor receives the short press signal, it increases the currently displayed upper limit threshold value by 1 (or decreases by 1, the specific increase or decrease direction can be set in the system according to user needs, and the default is generally to increase by 1), and updates the upper limit threshold display on the OLED display in real time through the display driver circuit. If the user long presses the SET button, the core processor will continue to detect the long press state of the button, and continuously increase (or decrease) the upper limit threshold value according to the preset continuous increase and decrease speed, and update the display in real time. During the operation, the user can stop the button operation at any time. When there is no button operation within 5 seconds, the core processor believes that the user has completed the upper limit value adjustment, stores the currently displayed value as the final upper limit threshold, and automatically returns to the main function interface. The OLED display also switches back to the main function interface display content; The logic of the lower limit adjustment menu is similar to that of the upper limit adjustment. After the user presses the MODE button, the core processor guides the user to the lower limit adjustment menu. The user can fine-tune the lower limit threshold by short-pressing or long-pressing the MODE button again. After the operation is completed and there is no key operation for 5 seconds, the system automatically saves the adjusted lower limit threshold and returns to the main function interface. When the user needs to perform more advanced parameter settings or function switching, long press the SET key + MODE key combination. At this time, the SET key and MODE key of the key unit are pressed at the same time, and the generated electrical signal changes are transmitted to the core processor of the control circuit unit through the key detection circuit. After the core processor recognizes the long press combination action of the SET key and MODE key, it enters the function menu interface; In the function menu interface, the OLED display shows multiple function options in a list format, such as normally open / normally closed settings, Chinese-English switching, key lock / unlock, parameter reset, etc. Users can switch between different function options by briefly pressing the SET key (equivalent to the left button). Each time the SET key is pressed, the cursor on the screen moves between different function options, indicating the currently selected function. When the cursor moves to the desired function option, the user briefly presses the MODE key (equivalent to the right button) to confirm the selection and enter the setting interface for that function; For example, when the user selects the normally open / normally closed setting function and enters the setting interface, the OLED display will display the current normally open / normally closed state and provide prompt information for switching between the two states. The user selects the state switch by short pressing the SET key or the MODE key. After confirming the selection, the core processor saves the new normally open / normally closed state setting and returns to the function menu interface. For the Chinese-English switching function, after selecting this function, the user enters the setting interface and presses the corresponding button to switch the display language from Chinese to English or from English to Chinese. The key lock / unlock function allows the user to lock the key operation when needed to prevent misoperation. In the locked state, long pressing the SET key + MODE key combination can unlock it. The parameter reset function can restore all parameters of the sensor to the factory default settings, making it convenient for the user to perform system initialization operations when needed. During the entire function menu operation process, every step of the user's operation will receive clear feedback through the OLED display to ensure the accuracy and convenience of the operation; 3) Signal output and status feedback The output signal state of the output unit is completely controlled by the control circuit unit based on the liquid level detection results and threshold settings. For example, in an NPN normally open (NO) switch, when the detected target liquid level exceeds the upper threshold, the control circuit unit's indicator light and signal output circuit output a high-level signal as the upper limit switch, and also output a high-level signal as the lower limit switch, while the analog output remains at 4mA. This is because at this point, the liquid level is above the upper threshold, and both threshold switches should be in the triggered state. However, when the liquid level exceeds the upper threshold, the analog output outputs a minimum value of 4mA according to preset logic. For example, in an oil tank level monitoring system, when the tank level exceeds the upper threshold, the upper limit switch outputs a high-level signal, which can be used to trigger an alarm to alert personnel of the high tank level. The lower limit switch also outputs a high-level signal, but in this case, the lower limit switch may not participate in actual control actions and only serves as a feedback signal for system status. The analog output of 4mA can be transmitted to the remote monitoring system to inform it of the current high liquid level. When the target liquid level is between the upper and lower thresholds, the control circuit unit controls the upper limit switch to output a low-level signal and the lower limit switch to output a high-level signal. The analog output then varies linearly between 4mA and 20mA, depending on the specific position of the liquid level within the threshold range. For example, if the liquid level is at the midpoint of the threshold range, the analog output may be around 12mA. In practical applications, this analog output method can provide more accurate liquid level information to the external control system, facilitating precise control of the liquid level. For example, in a chemical reactor liquid level control system, based on the analog output liquid level signal, the control system can precisely adjust the opening of the feed and discharge valves to ensure that the reactor liquid level remains stable within the appropriate range. When the target liquid level is lower than the lower limit threshold, the control circuit unit causes the upper limit switch to output a low level signal, the lower limit switch also outputs a low level signal, and the analog output becomes 20.

[0022] Also, see Figure 9-12 , in the "Settings" interface on the menu homepage, press and hold the SET key + MODE key combination for more than 1 second to enter the expert menu; When the liquid level sensor is in use, a hysteresis value is also provided. When the target liquid level fluctuates around the set threshold, the hysteresis value is used to maintain the stability of the signal output state; specifically: For example, if the threshold is set to 100, then when the target liquid level is 99, signal 1 will be output, and when the target liquid level is 101, signal 0 will be output; at this time, if the liquid level fluctuates for some reason, then the measured target liquid level may jitter repeatedly between 99 and 101, and the output signal may continuously output signal 1 and signal 0; at this time, set the hysteresis value to 4, and the threshold is still 100, then when the target liquid level increases from 98 to 102, it will still output 0, and will not output 1 until it exceeds 102; when the target liquid level decreases from 102 to 98, it will still keep outputting 1, and will not output 0 until it is less than 98; when the target liquid level jitters between 98 and 102, the signal output remains in its original state, and will not jump to the signal until it is greater than 102 or less than 98.

[0023] See also Figure 11 The signal value indicates the strength of the current target signal. A higher strength indicates a higher signal value. During installation, you can use this value to determine if the installation angle is optimal. A higher signal value indicates a more positive installation angle. The target value indicates the distance to the current target, in mm.

[0024] See also Figure 12 When the target exceeds the measuring range or the angle deviation of the target plane is too large, the interface is displayed as shown in the figure.

[0025] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A digital ultrasonic liquid level sensor, comprising a first housing (1) and a second housing (2), characterized in that: The device further comprises a control circuit unit (3), an ultrasonic probe (4), a key unit (5), a display unit (6), an indication unit (7), and an output unit (8) built into the first shell (1) and the second shell (2). The control circuit unit (3) is electrically connected to the ultrasonic probe (4), the key unit (5), the display unit (6), the indication unit (7), and the output unit (8), respectively. The key unit (5) is used to realize one-key setting of threshold values ​​and parameter adjustment. The display unit (6) is used to display measurement data, threshold parameters, and operating status information in real time. Threshold setting and data viewing can be independently completed without relying on external debugging tools.

2. The digital ultrasonic liquid level sensor according to claim 1, characterized in that: The button unit (5) includes two independent buttons, namely a SET button and a MODE button; the SET button is used to set the upper threshold value and enter the upper limit value adjustment menu, and the MODE button is used to set the lower threshold value and enter the lower limit value adjustment menu; The display unit (6) is an OLED display screen, which can display the distance value, upper threshold value, lower threshold value, output status and received signal strength of the real-time detection target, and the numerical unit is mm.

3. The digital ultrasonic liquid level sensor according to claim 1, characterized in that: The control circuit unit (3) comprises a power supply circuit, an ultrasonic excitation circuit, an ultrasonic receiving circuit, a key detection circuit, a display screen drive circuit, a temperature detection circuit, an indicator light and a signal output circuit.

4. The digital ultrasonic liquid level sensor according to claim 3, characterized in that: The signal output circuit is connected to an output unit (8), and the output unit (8) supports three output signals: an upper threshold switching value, a lower threshold switching value, and a threshold interval analog value.

5. The digital ultrasonic liquid level sensor according to claim 1, characterized in that: Also included is an echo signal detection algorithm, the algorithm comprising: Step 1: Locate the start position, peak position and end position of the transmitted signal wave; Step 2: Detect the received echo signal starting from the peak position of the transmitted signal wave to identify the superimposed echo and reduce the detection blind area.

6. The digital ultrasonic liquid level sensor according to claim 1, characterized in that: The display unit (6) also displays the current output state on the main function interface, wherein a solid circle indicates that the corresponding threshold signal output is 1, and a hollow circle indicates that the corresponding threshold signal output is 0.

7. The digital ultrasonic liquid level sensor according to claim 1, characterized in that: The indicating unit (7) is configured as a status indicator light, which is always on when there is no target object within the measuring range, and flashes when there is a target object within the measuring range.

8. The digital ultrasonic liquid level sensor according to claim 1, characterized in that: It has an automatic key lock function: it will automatically lock the keys if there is no operation for more than 5 minutes; in the key lock state, press and hold the SET key and MODE key combination for more than 1 second to unlock.

9. A method for setting a threshold value of a digital ultrasonic liquid level sensor, applied to the sensor according to any one of claims 1 to 9, characterized in that: Including: when the detection target is at the threshold position to be set, press and hold the SET button for more than 2 seconds to set the upper threshold with one click, or press and hold the MODE button for more than 2 seconds to set the lower threshold with one click. After the setting is completed, the display unit will synchronously update and display the set threshold.

10. The threshold setting method according to claim 9, characterized in that: Also includes: A hysteresis value is provided, and when the target liquid level fluctuates around a set threshold value, the hysteresis value is used to maintain the stability of the signal output state.

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