Piezoelectric ultrasonic sensors use the properties of piezoelectric materials to convert sound waves into electrical signals. The sensor consists of piezoelectric materials, carriers, and electrodes. When there are sound waves in the medium to be measured, the piezoelectric material is deformed by the pressure of the sound waves, resulting in an electric charge, which is then converted into an electrical signal output.
Piezoelectric ultrasonic sensors are mainly composed of piezoelectric materials, metal electrodes, support plates, and packaging materials. Piezoelectric materials are typically quartz or ceramic, and metal electrodes are used to collect and direct charge. The support plate provides structural support for the sensor and acts as a protection and holding of the sensor. The packaging material is used to protect the internal components of the sensor in the external environment.
1) High frequency: Piezoelectric ultrasonic sensors have a high working frequency, usually in the range of tens of kHz to hundreds of kHz.
2) High accuracy: Due to the short wavelength of ultrasound, the sensor can provide precise measurements at small distances.
3) Non-contact: The ultrasonic sensor does not need to be in direct contact with the target object, and can be measured within a certain distance.
4) High reliability: The characteristics of piezoelectric materials make the sensor have good mechanical and thermal stability, and are suitable for long-term use in industrial environments.
5) Fast response: The sensor can detect and measure the target object in real time.
The operating principle of piezoelectric ultrasonic sensors is based on the piezoelectric effect and the principle of reflection. When an applied voltage is applied, the ceramic sheet undergoes mechanical vibrations that convert electrical energy into ultrasonic energy. When a sound wave encounters a target object, a portion of the sound wave is reflected back and received by the sensor's back cavity. These sound waves vibrate the ceramic sheet again, generating an electrical signal.
Piezoelectric ultrasonic sensors are widely used in many fields, including but not limited to the following:
1) Ranging and obstacle detection: It is used in scenarios such as robot navigation and intelligent parking systems that need to measure distances and detect obstacles.
2) Non-contact liquid level detection: It is used for liquid level detection of oil tanks, water tanks and other containers, with the advantages of high precision and fast response.
3) Object detection and classification: It can be applied to the process of object positioning, size measurement and classification in industrial production.
4) Biomedical applications: such as ultrasound image generation, blood flow measurement, medical diagnosis, etc.
In the manufacturing process of piezoelectric ultrasonic sensors, key processing processes include:
1. Preparation of piezoelectric materials: select appropriate piezoelectric materials, such as ferroelectric single crystals, piezoelectric ceramics, etc., and design the shape of the materials. The material is processed into the desired shape and size through cutting, grinding, polishing, and other processes.
2. Construct a piezoelectric sensor: assemble the prepared piezoelectric material and metal electrode together to form the structure of the piezoelectric sensor. Bonding, welding, etc., are usually used to fix the electrode on the surface or inside the material.
3. Electrode connection: connect the electrode lead of the sensor to the circuit board or connector to realize the input and output of the electrical signal.
4. Packaging protection: In order to protect the sensor from interference and damage from the external environment, the sensor needs to be packaged. Common packaging methods include injection molded packaging, silicone packaging, etc., to ensure the durability and stability of the sensor.
5. Overall test: Conduct an overall test on the packaged ultrasonic sensor, evaluate its performance indicators such as frequency response, sensitivity, linearity, etc., and conduct quality inspection to ensure that the sensor meets the design requirements.
6. Calibration and debugging: calibrate and debug the sensor to ensure the accuracy and stability of its output signal and input signal. The calibration process typically involves the use of test equipment such as signal generators, oscilloscopes, etc.
7. Final product test: The final product test is carried out on the calibrated and debugged sensor to verify its performance and stability in practical applications.
Sensors may malfunction due to factors such as the working environment, usage method, and material aging. The following are common analyses and solutions to piezoelectric ultrasonic sensor failures:
Fault 1: The output signal is abnormal or there is no output.
Solution: 1. First, check whether the sensor power supply is connected normally to ensure that the power supply is stable and within the rated voltage range.
2. Check the connection between the sensor and the instrument to ensure that the connection is good and not loose or blocked.
3. Check whether the transmitting and receiving components of the sensor are damaged, and replace them with new ones if necessary.
4. Check whether the drive circuit is working normally, and repair or replace the drive circuit if necessary.
Fault 2: The measurement accuracy is reduced.
Solution: 1. Check the distance between the sensor and the object, ensure that it is within the effective measurement distance, and avoid being too close or too far.
2. Check the medium between the sensor and the surface of the object, and clean or replace the medium if necessary to ensure that the signal transmission between the sensor and the object is good.
3. Check whether the sensor is interfered with by the outside world, and if necessary, increase shielding measures or change the working environment.
4. Check whether the transmitting and receiving components of the sensor are damaged or aged, and replace them with new ones if necessary.
Fault 3: The operating frequency is offset.
Solution: 1. Check the driving circuit and control signal of the sensor to ensure that the working frequency is set correctly.
2. Check whether the working environment temperature of the sensor is stable, and if necessary, increase temperature compensation measures or adjust the working temperature range.
3. Check whether the sensor material is aged or damaged, and replace it with a new material if necessary.
Fault 4: The signal amplitude is unstable.
Solution: 1. Check whether the power supply voltage of the sensor is stable, and add a voltage stabilizer or filter if necessary.
2. Check whether there is spurious signal interference in the output line of the sensor, and if necessary, increase shielding measures or adjust the line layout.
3. Check whether the transmitting and receiving components of the sensor are damaged, and replace them with new ones if necessary.
4. Check whether there is vibration or other interference sources in the working environment of the sensor, and if necessary, increase shock absorption measures or change the working environment.