A feedback ultrasonic liquid level alarm device and its alarm method

Abstract

This invention discloses a feedback-type ultrasonic liquid level alarm device and method. A first ultrasonic transducer and a second ultrasonic transducer are installed inside a housing and connected via a signal amplification circuit and a frequency-selective amplification circuit. When the housing gap is filled with liquid, the first and second ultrasonic transducers are stimulated to generate an AC signal to detect in real time whether the actual liquid level has reached the predetermined level. When the housing gap is filled with air, the first and second ultrasonic transducers cannot be stimulated, and therefore no AC signal is generated, indicating that the actual liquid level has not reached the predetermined level. Ultimately, this method monitors whether the liquid level in an airborne wastewater storage tank has reached the set position, reducing the weight and size of the device, and the detection process is simple and reliable.

Description

Technical Field

[0001] This invention belongs to the technical field of ultrasonic liquid level detection, and relates to a feedback ultrasonic liquid level alarm device and its alarm method. Background Technology

[0002] Wastewater treatment systems are an indispensable part of aircraft, and wastewater storage tanks are a crucial component of these systems. Level detection in wastewater storage tanks plays a vital role in the proper functioning of the entire system. While wastewater storage tank level detection is typically point-based, aircraft wastewater storage tanks often have a capsule structure with complex internal media containing impurities and sediments, making maintenance and repair difficult. Therefore, improving equipment reliability, miniaturizing the design, and minimizing the influence of complex media on measurement results are of paramount importance.

[0003] Contact measurement methods share the common characteristic that the sensing element is in contact with the liquid being measured, which poses risks such as wear, easy adhesion and corrosion by the liquid, and is prone to blockage and insensitivity. Among non-contact measurement methods, ultrasonic measurement is relatively simple, less susceptible to electromagnetic interference, suitable for airborne applications, and relatively low in cost, making it easy to promote for civilian use. It is widely used in industrial production and scientific research.

[0004] Common ultrasonic liquid level alarm methods often employ a microprocessor to generate a PWM wave via software to excite the ultrasonic transducer and collect the detection results. For airborne liquid level alarm devices, this approach is not conducive to reducing product weight and size; furthermore, when applied to aircraft, this method requires software airworthiness testing, significantly increasing development time and cost, and also posing a challenge to the supplier's software system.

[0005] Therefore, in view of the above-mentioned defects in the liquid level detection of existing airborne wastewater treatment systems, the present invention discloses a feedback ultrasonic liquid level alarm device and its alarm method. Summary of the Invention

[0006] The purpose of this invention is to provide a feedback ultrasonic liquid level alarm device and its alarm method for monitoring whether the liquid level in an airborne wastewater storage tank has reached a set position, which helps to reduce the weight and volume of the device, and the detection process is simple and reliable.

[0007] This invention is achieved through the following technical solution:

[0008] A feedback-type ultrasonic liquid level alarm device includes a first ultrasonic transducer and a second ultrasonic transducer. The first and second ultrasonic transducers are symmetrically arranged inside a housing, and a gap is provided between the first and second ultrasonic transducers to communicate with the external environment. The first ultrasonic transducer is connected to the second ultrasonic transducer in sequence through a signal amplification circuit and a frequency selective amplification circuit. The output terminal of the second ultrasonic transducer is connected to the input terminal of the first ultrasonic transducer.

[0009] To better realize the present invention, the output terminal of the frequency selective amplifier circuit is further connected to the input terminal of the voltage comparator circuit and the input terminal of the second ultrasonic transducer, respectively, and the output terminal of the voltage comparator circuit is provided with a discrete output port.

[0010] To better realize the present invention, the signal amplification circuit further includes a first-stage amplification circuit and a second-stage amplification circuit connected in sequence. The first-stage amplification circuit includes a first transistor, and the second-stage amplification circuit includes a second transistor. The first transistor operates in the amplification region, and the second transistor operates in the saturation region.

[0011] To better realize the present invention, the first-stage amplifier circuit further includes a first base capacitor disposed at the base of the first transistor, the output terminal of the first ultrasonic transducer is connected to the input terminal of the first base capacitor, and the collector of the first transistor is connected to the base of the second transistor.

[0012] To better realize the present invention, the secondary amplifier circuit further includes a second base capacitor disposed at the base of the second transistor, and the collector of the first transistor is connected to the input terminal of the second base capacitor.

[0013] To better realize the present invention, the frequency selective amplifier circuit further includes a frequency selective transistor and a frequency selective base capacitor. The frequency selective base capacitor is disposed at the base of the frequency selective transistor, and the input terminal of the frequency selective base capacitor is connected to the collector of the second transistor.

[0014] To better realize the present invention, the collector of the frequency-selective transistor is connected to the input terminal of the second ultrasonic transducer, and the emitter of the frequency-selective transistor is connected to the input terminal of the voltage comparator circuit.

[0015] To better realize the present invention, the collector of the frequency-selective transistor is further connected to the input terminal of the second ultrasonic transducer through an LC oscillation circuit, and the emitter of the frequency-selective transistor is connected to the input terminal of the voltage comparator circuit through a low-pass filter circuit.

[0016] A feedback-type ultrasonic liquid level alarm method involves placing a housing containing a first ultrasonic transducer and a second ultrasonic transducer at a predetermined liquid level. The second ultrasonic transducer emits ultrasonic waves towards the first ultrasonic transducer. When the gap in the housing is filled with liquid, the ultrasonic waves pass through the liquid and are emitted to the first ultrasonic transducer, exciting it to generate an ultrasonic AC signal. This AC signal is amplified by a signal amplification circuit, frequency-selected by a frequency-selective amplification circuit, and then input to the second ultrasonic transducer for feedback excitation. When the gap in the housing is filled with air, the ultrasonic waves undergo total reflection at the interface between the housing and the air, and the first ultrasonic transducer is not excited.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0018] (1) The present invention forms a feedback ultrasonic liquid level alarm device by means of a first ultrasonic transducer and a second ultrasonic transducer. A feedback mechanism is formed between the circuit and the ultrasonic transducer. When the actual liquid level reaches the predetermined liquid level, the ultrasonic transducer can be stimulated by feedback. No additional stimulation is required through a processor, which reduces the types of components. Therefore, the weight and volume of the alarm device can be further reduced and miniaturized.

[0019] (2) The feedback ultrasonic liquid level alarm method proposed in this invention outputs discrete signals that are directly collected by the host computer. The number of interface cables is reduced, which simplifies the product structure, effectively reduces the overall size and weight of the product, lowers the manufacturing cost, and improves the economic efficiency of the product.

[0020] (3) The feedback ultrasonic liquid level alarm device proposed in this invention has a rated power supply voltage as low as 3.3V, an operating current of 10~20mA, and lower power consumption.

[0021] (4) The present invention outputs discrete signals for acquisition by the host computer through circuit design, which reduces the microprocessor and its surrounding circuits, reduces the failure rate of components, and improves product reliability;

[0022] (5) The feedback ultrasonic liquid level alarm device proposed in this invention includes a pure hardware circuit and outputs a discrete signal. It does not require software control of the microprocessor to generate a PWM wave to excite the ultrasonic transducer transmitter, thus avoiding software-related airworthiness work and saving manpower-related costs. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the architecture of a feedback-type ultrasonic liquid level alarm device.

[0024] Figure 2 This is a circuit diagram showing the connection between the first ultrasonic transducer and the second ultrasonic transducer.

[0025] Figure 3 This is a schematic diagram of the first amplifier circuit;

[0026] Figure 4 This is a schematic diagram of the second amplifier circuit;

[0027] Figure 5 This is a schematic diagram of a frequency-selective amplifier circuit;

[0028] Figure 6 This is a schematic diagram of a voltage comparator circuit. Detailed Implementation

[0029] The following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0030] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is intended to include the plural form as well. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0031] For ease of description, the words "up," "down," "left," and "right" appearing in this invention only indicate that they are consistent with the up, down, left, and right directions of the accompanying drawings themselves, and do not limit the structure. They are merely for the purpose of facilitating the description of this invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] Terminology Explanation: The terms "installation," "connection," "linking," and "fixing" in this invention should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction relationship between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] Example 1:

[0034] This embodiment provides a feedback-type ultrasonic liquid level alarm device, such as... Figure 1As shown, it includes a first ultrasonic transducer and a second ultrasonic transducer. The first ultrasonic transducer and the second ultrasonic transducer are symmetrically arranged inside the housing, and a gap is provided between the first ultrasonic transducer and the second ultrasonic transducer to communicate with the external environment. The first ultrasonic transducer is connected to the second ultrasonic transducer in sequence through a signal amplification circuit and a frequency selective amplification circuit. The output terminal of the second ultrasonic transducer is connected to the input terminal of the first ultrasonic transducer.

[0035] The housing is installed to the predetermined liquid level. When the actual liquid level reaches the predetermined level, the gap is filled with liquid. The ultrasonic waves emitted by the second ultrasonic transducer can penetrate the liquid and reach the first ultrasonic transducer. After receiving the ultrasonic waves, the first ultrasonic transducer generates an alternating current signal. This signal is amplified by a signal amplification circuit, selected by a frequency-selective amplification circuit, and then input to the second ultrasonic transducer to provide feedback excitation and encourage it to emit ultrasonic waves again. When the actual liquid level has not reached the predetermined level, the gap is filled with air. The ultrasonic waves emitted by the second ultrasonic transducer undergo total reflection at the interface between the air and the housing. At this time, the ultrasonic waves cannot reach the first ultrasonic transducer, and the first ultrasonic transducer is not excited by the ultrasonic waves. Therefore, the second ultrasonic transducer does not receive the feedback alternating current signal. By monitoring whether the second ultrasonic transducer receives the alternating current signal, it can be determined whether the actual liquid level has reached the predetermined level.

[0036] Example 2:

[0037] A feedback-type ultrasonic liquid level alarm device, improved based on Embodiment 1, such as... Figure 2 As shown, the output terminal of the frequency selective amplifier circuit is connected to the input terminal of the voltage comparator circuit and the input terminal of the second ultrasonic transducer, respectively. The output terminal of the voltage comparator circuit is provided with a discrete output port.

[0038] The discrete output port is connected to an external signal detection device. When the gap is filled with liquid, the first ultrasonic transducer is excited and generates an AC signal. The AC signal is amplified and frequency-selected before being input to the voltage comparison circuit. Since the AC signal is greater than the comparison voltage, the voltage comparison circuit outputs a high-level signal to the external signal detection device through the discrete output port. When the gap is filled with air, the first ultrasonic transducer does not generate an AC signal, and the voltage comparison circuit cannot receive the AC signal or can only receive ambient noise. Therefore, the voltage comparison circuit outputs a low-level signal to the external signal detection device through the discrete output port.

[0039] like Figure 2As shown, interface J1 is connected to the first ultrasonic transducer, interface J2 is connected to the second ultrasonic transducer, R1-R25 represent resistors numbered 1-25, C1-C16 represent capacitors numbered 1-16, V1, V2, V6, V7 represent diodes numbered 1, 2, 6, 7, V3-V5 represent transistors numbered 3-5, and L1, L2 represent inductors numbered 1 and 2.

[0040] The other parts of this embodiment are the same as those in Embodiment 1, so they will not be described again.

[0041] Example 3:

[0042] A feedback-type ultrasonic liquid level alarm device, improved based on Embodiment 1 or 2, such as... Figures 2-4 As shown, the signal amplification circuit includes a first-stage amplification circuit and a second-stage amplification circuit connected in sequence. The first-stage amplification circuit includes a first transistor, and the second-stage amplification circuit includes a second transistor. The first transistor operates in the amplification region, and the second transistor operates in the saturation region. The first-stage amplification circuit also includes a first base capacitor disposed at the base of the first transistor. The output terminal of the first ultrasonic transducer is connected to the input terminal of the first base capacitor, and the collector of the first transistor is connected to the base of the second transistor. The second-stage amplification circuit also includes a second base capacitor disposed at the base of the second transistor, and the collector of the first transistor is connected to the input terminal of the second base capacitor.

[0043] The first ultrasonic transducer is connected to the input terminal of the first base capacitor (i.e., capacitor C1) in the first-stage amplifier circuit, serving as the AC input of the amplifier circuit. The first-stage amplifier circuit is a common-emitter amplifier circuit, and its first transistor (i.e., transistor V3) operates in the amplification region, amplifying the AC signal output by the first ultrasonic transducer.

[0044] The collector output of the first transistor in the first-stage amplifier circuit is connected to the input terminal of the second base capacitor (i.e., capacitor C4) in the second-stage amplifier circuit. The second-stage amplifier circuit is a common-emitter amplifier circuit, which operates in the saturation region. The second-stage amplifier circuit further amplifies the amplified signal output from the first-stage amplifier circuit into an AC signal with stable amplitude.

[0045] The collector output of the second transistor (i.e., transistor V4) in the secondary amplifier circuit is connected to the input terminal of the frequency selective amplifier circuit, which includes an LC oscillator circuit with a center frequency of 0.8-1MHz.

[0046] The other parts of this embodiment are the same as those in Embodiment 1 or 2, so they will not be described again.

[0047] Example 4:

[0048] A feedback-type ultrasonic liquid level alarm device, improved based on any one of embodiments 1-3, such as... Figure 5 As shown, the frequency-selective amplifier circuit includes a frequency-selective transistor (i.e., transistor V5) and a frequency-selective base capacitor (i.e., capacitor C7). The frequency-selective base capacitor is located at the base of the frequency-selective transistor, and its input terminal is connected to the collector of the second transistor. Figure 6 As shown, the collector of the frequency-selective transistor is connected to the input terminal of the second ultrasonic transducer, and the emitter of the frequency-selective transistor is connected to the input terminal of the voltage comparator circuit. The collector of the frequency-selective transistor is connected to the input terminal of the second ultrasonic transducer through an LC oscillation circuit, and the emitter of the frequency-selective transistor is connected to the input terminal of the voltage comparator circuit through a low-pass filter circuit.

[0049] The LC oscillation circuit has a center frequency of 0.8-1MHz. It performs frequency selection filtering on the AC signal, and then inputs the selected AC signal to the second ultrasonic transducer. The low-pass filter circuit converts the AC signal into a DC signal, which is then input to the voltage comparator circuit.

[0050] The other parts of this embodiment are the same as those in Embodiment 4, so they will not be described again.

[0051] Example 5:

[0052] A feedback ultrasonic liquid level alarm method, implemented based on the feedback ultrasonic liquid level alarm device described in any one of Examples 1-4, involves placing a housing containing a first ultrasonic transducer and a second ultrasonic transducer at a predetermined liquid level. The second ultrasonic transducer emits ultrasonic waves towards the first ultrasonic transducer. When the gap in the housing is filled with liquid, the ultrasonic waves pass through the liquid and are emitted to the first ultrasonic transducer, exciting it to generate an ultrasonic AC signal. The AC signal is amplified by a signal amplification circuit, frequency-selected by a frequency-selective amplification circuit, and then input to the second ultrasonic transducer for feedback excitation. When the gap in the housing is filled with air, the ultrasonic waves undergo total reflection at the interface between the housing and the air, and the first ultrasonic transducer is not excited.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A feedback type ultrasonic liquid level alarm device comprising a first ultrasonic transducer, a second ultrasonic transducer, characterized by, The first ultrasonic transducer and the second ultrasonic transducer are symmetrically arranged in the shell, and a gap in communication with the external environment is arranged between the first ultrasonic transducer and the second ultrasonic transducer; the first ultrasonic transducer is connected with the second ultrasonic transducer through a signal amplification circuit and a frequency selection amplification circuit in sequence, and an output end of the second ultrasonic transducer is connected with an input end of the first ultrasonic transducer.

2. A feedback type ultrasonic liquid level alarm device according to claim 1, wherein An output end of the frequency selection amplification circuit is connected with an input end of a voltage comparison circuit and an input end of the second ultrasonic transducer, and an output end of the voltage comparison circuit is provided with a discrete quantity output port.

3. A feedback ultrasonic liquid level alarm device according to claim 2, wherein The signal amplification circuit comprises a first-stage amplification circuit and a second-stage amplification circuit connected in sequence, the first-stage amplification circuit comprises a first triode, the second-stage amplification circuit comprises a second triode, the first triode works in an amplification zone, and the second triode works in a saturation zone.

4. A feedback type ultrasonic liquid level alarm device according to claim 3, wherein The first-stage amplification circuit further comprises a first base capacitor arranged at a base of the first triode, an output end of the first ultrasonic transducer is connected with an input end of the first base capacitor, and a collector of the first triode is connected with a base of the second triode.

5. A feedback ultrasonic liquid level alarm device according to claim 4, wherein The second-stage amplification circuit further comprises a second base capacitor arranged at a base of the second triode, and a collector of the first triode is connected with an input end of the second base capacitor.

6. A feedback ultrasonic liquid level alarm device according to claim 5, wherein The frequency selection amplification circuit comprises a frequency selection triode and a frequency selection base capacitor, the frequency selection base capacitor is arranged at a base of the frequency selection triode, and an input end of the frequency selection base capacitor is connected with a collector of the second triode.

7. A feedback ultrasonic liquid level alarm device according to claim 6, wherein A collector of the frequency selection triode is connected with an input end of the second ultrasonic transducer, and an emitter of the frequency selection triode is connected with an input end of the voltage comparison circuit.

8. A feedback ultrasonic liquid level alarm device according to claim 6, wherein The collector of the frequency selection triode is connected with the input end of the second ultrasonic transducer through an LC oscillation circuit, and the emitter of the frequency selection triode is connected with the input end of the voltage comparison circuit through a low-pass filter circuit.

9. A feedback ultrasonic liquid level alarm method, implemented based on the feedback ultrasonic liquid level alarm device of any one of claims 1-8, characterized in that, The shell with the first ultrasonic transducer and the second ultrasonic transducer arranged therein is placed at a predetermined liquid level, and the second ultrasonic transducer emits ultrasonic waves to the first ultrasonic transducer; when the gap in the shell is filled with liquid, the ultrasonic waves pass through the liquid and are emitted to the first ultrasonic transducer to excite the first ultrasonic transducer, so as to generate an ultrasonic alternating current signal in the first ultrasonic transducer, the alternating current signal is amplified through the signal amplification circuit, is frequency-selected through the frequency selection amplification circuit, and is then input to the second ultrasonic transducer to feedback excite the second ultrasonic transducer; when the gap in the shell is filled with air, the ultrasonic waves are totally reflected at the interface between the shell and the air, and the first ultrasonic transducer is not excited.

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