Capacitive liquid level sensor

Abstract

The utility model discloses a capacitive liquid level sensor which comprises a power input module, an anti-reverse-connection anti-interference filter circuit, a high-precision LDO voltage stabilization output module, a reference signal reference circuit, a signal induction filter circuit, a signal input module, an MCU main control circuit, an LED work indication module, a signal control output protection and drive circuit and a signal output module. The power input module is connected with the anti-reverse-connection anti-interference filter circuit, and the anti-reverse-connection anti-interference filter circuit is further connected with the high-precision LDO voltage stabilization output module. According to the utility model, an external terminal is adopted to effectively identify high level through software, and the sensitivity is automatically adjusted, so that the sensitivity drift caused by the aging error problem of the potentiometer is avoided.

Description

TECHNICAL FIELD

[0001] The utility model relates to sensor technical field, especially a kind of capacitive liquid level sensor. BACKGROUND

[0002] In industrial production and daily life, accurate measurement of liquid level is very important. For example, in the production process of chemical, petroleum, food, pharmaceutical and other industries, the liquid level of various liquids needs to be accurately monitored and controlled to ensure the smooth progress of production, improve production efficiency and product quality.

[0003] With the continuous progress of electronic technology, capacitive measurement technology has developed rapidly. The emergence of high-precision capacitive measurement chip and circuit makes capacitive liquid level detection technology achieve more accurate measurement. At the same time, the development of electronic technology also makes the liquid level detection system realize the functions of signal processing, transmission and display, etc., which improves the automation degree and convenience of liquid level detection.

[0004] The basic principle of capacitance is the ability of capacitor to store electric charge, which is composed of two electrodes and intermediate dielectric. Its capacitance depends on the distance between electrodes, effective area of electrode and dielectric constant of dielectric. When different media are inserted between the two plates of capacitor, the capacitance of capacitor will change. This provides a theoretical basis for capacitive liquid level detection technology, that is, by measuring the change of capacitance to reflect the change of liquid level.

[0005] Usually, the measurement results of capacitive liquid level sensor on the market are easily disturbed by factors such as environmental temperature and liquid wall hanging, which will seriously affect the measurement results. UTILITY MODEL CONTENT

[0006] In order to make up for the shortcomings of the prior art, the application provides a capacitive liquid level sensor to solve the problems existing in the prior art.

[0007] In order to solve the above technical problems, the utility model provides the following technical scheme:

[0008] The utility model provides a capacitive liquid level sensor, including power input module, prevent reverse connection anti -interference filter circuit, high accuracy LDO voltage stabilizing output module, reference signal reference circuit, signal induction filter circuit, signal input module, MCU main control circuit, LED work indication module, signal control output protection and driving circuit and signal output module, power input module connects prevent reverse connection anti -interference filter circuit, prevent reverse connection anti -interference filter circuit still connects high accuracy LDO voltage stabilizing output module, high accuracy LDO voltage stabilizing output module still connects reference signal reference circuit, signal induction filter circuit and MCU main control circuit respectively, signal induction filter circuit still connects signal input module and MCU main control circuit respectively, reference signal reference circuit still connects MCU main control circuit, MCU main control circuit still connects LED work indication module and signal control output protection and driving circuit respectively, signal control output protection and driving circuit still connects signal output module.

[0009] As a further technical scheme of the utility model: the input voltage of the power input module is DC12-24V.

[0010] As a further technical scheme of the utility model: the MCU main control circuit adopts CMS32L051QN20 chip.

[0011] As a further technical scheme of the utility model: the reference signal reference circuit adopts three-terminal adjustable reference source.

[0012] As a further technical scheme of the utility model: the prevent reverse connection anti -interference filter circuit is composed of prevent reverse connection diode, resistance, filter capacitor.

[0013] One or more technical schemes provided in the embodiment of the application have at least the following technical effects or advantages:

[0014] The utility model adopts the mode that external wiring end passes through software effective identification high level, and the sensitivity of automatic adjustment avoids the problem of the drift of sensitivity caused by the aging error of potentiometer. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is the overall block diagram of capacitive liquid level sensor.

[0016] Figure 2 It is the circuit diagram of capacitive liquid level sensor.

[0017] Figure 3 It is the internal signal processing flow chart of MCU. DETAILED DESCRIPTION

[0018] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] like Figures 1-2 As shown, a capacitive liquid level sensor includes a power input module, an anti-reverse polarity and anti-interference filter circuit, a high-precision LDO voltage-regulated output module, a reference signal base circuit, a signal sensing filter circuit, a signal input module, an MCU main control circuit, an LED operation indicator module, a signal control output protection and drive circuit, and a signal output module. The power input module is connected to the anti-reverse polarity and anti-interference filter circuit, which is also connected to the high-precision LDO voltage-regulated output module. The high-precision LDO voltage-regulated output module is also connected to the reference signal base circuit, the signal sensing filter circuit, and the MCU main control circuit, respectively. The signal sensing filter circuit is also connected to the signal input module and the MCU main control circuit, and the reference signal base circuit is also connected to the MCU main control circuit. The MCU main control circuit is also connected to the LED operation indicator module and the signal control output protection and drive circuit, respectively. The signal control output protection and drive circuit is also connected to the signal output module. This design utilizes the latest international leading technology and can effectively address the effects of liquids sticking to walls, such as hand sanitizer, honey, and disinfectant. Furthermore, when high sensor sensitivity is required, it effectively prevents false triggering around the sensor. This design uses external terminals to effectively identify high levels through software and automatically adjust the sensitivity to avoid sensitivity drift due to aging errors of the potentiometer.

[0020] Here's how it works:

[0021] Capacitive liquid level sensors measure liquid levels by utilizing the principle that the capacitance of a capacitor changes with changes in the medium between its two plates. Capacitive level sensors typically consist of a metal sensing surface as one plate and a liquid level tube as the other, forming a capacitor between them. When liquid enters the sensor, the medium between the metal sensing surface and the level tube changes, causing a change in capacitance. By sampling the capacitance value using a microcontroller's analog-to-digital converter (ADC), the difference between the presence and absence of liquid can be determined. A description of each circuit module is provided below.

[0022] Power input voltage stabilization circuit: This circuit is mainly composed of D5, D4, U5, U2, C14, and C10. It supports a DC input voltage of DC12-24V. The power input is connected in series with a diode and a transient diode to form anti-reverse connection and surge protection functions. The voltage stabilization uses a high-precision LDO output to ensure the stability of the microcontroller and the accuracy of AD sampling.

[0023] The sampling signal circuit: in order to improve the precision of the sensor, a reference signal generator is added on the hardware, which sends a high frequency signal by the single-chip microcomputer, and after being driven by the high-speed low-side gate of the chip U1, the selected frequency filter composed of R4, Q2, R2 and C4 is used, and then the RCπ type filter composed of D3 shaping and C7, R7 and C8 is used to filter to obtain a stable reference DC signal to the single-chip sampling. Another signal sampling circuit is composed of the selected frequency filter composed of devices R3, Q1, R1 and C1, and the stable superimposed signal obtained after the RCπ type filter composed of D2 shaping and C6, R5 and C5 is given to the single-chip to complete the sampling of the signal.

[0024] The MCU single-chip microcomputer main control circuit: mainly composed of U3, mainly completes the AD signal sampling and the output of the reference signal, controls the LED indication, and monitors and controls the output protection circuit.

[0025] The output signal protection circuit: the circuit is mainly composed of R18, F2, Q4, R17 and R19, when the output signal line is mistakenly connected to the power supply end, the product is powered on, the MCU detects the overcurrent signal through AD sampling, and quickly closes the MOS to start the protection circuit.

[0026] The main resources used by the single-chip microcomputer are timers, serial ports, memories, AD conversion, PWM modulation output, and the configuration and control of related IO ports. The software is used to set median filter, average filter, de-bouncing filter, fitting algorithm and the like to further improve the stability of the sampling data. The accuracy of the collected data is effectively ensured. The main software flow is as shown in Figure 3 .

[0027] For those skilled in the art, it is obvious that the utility model is not limited to the details of the above-mentioned exemplary embodiments, and can be realized in other specific forms without departing from the spirit or basic characteristics of the utility model. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, and the scope of the utility model is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the utility model.

[0028] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description manner of the specification is only for the sake of clarity, and those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment have been properly combined to form other embodiments which are easily understood by those skilled in the art.

Claims

1. A capacitive liquid level sensor comprising a power input module, an anti-reverse interference filter circuit, a high-precision LDO voltage stabilizing output module, a reference signal reference circuit, a signal sensing filter circuit, a signal input module, an MCU main control circuit, an LED working indication module, a signal control output protection and driving circuit, and a signal output module, characterized in that: The power input module is connected with the anti-reverse connection anti-interference filter circuit, the anti-reverse connection anti-interference filter circuit is further connected with the high-precision LDO voltage stabilizing output module, the high-precision LDO voltage stabilizing output module is further connected with the reference signal reference circuit, the signal sensing filter circuit and the MCU main control circuit respectively, the signal sensing filter circuit is further connected with the signal input module and the MCU main control circuit respectively, the reference signal reference circuit is further connected with the MCU main control circuit, the MCU main control circuit is further connected with the LED working indication module and the signal control output protection and driving circuit respectively, and the signal control output protection and driving circuit is further connected with the signal output module. ​ 2. A capacitive liquid level sensor according to claim 1, characterized in that The input voltage of the power input module is DC 12-24V.

3. A capacitive liquid level sensor according to claim 1, wherein, The MCU main control circuit adopts a CMS32L051QN20 chip.

4. A capacitive liquid level sensor according to claim 1, wherein, The reference signal reference circuit adopts a frequency signal generated by the MCU, which is rectified and filtered to form a reference reference source.

5. A capacitive liquid level sensor according to claim 1, wherein, The anti-reverse connection anti-interference filter circuit is composed of an anti-reverse connection diode, a resistor and a filter capacitor.

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