1. Working principle
The working principle of ultrasonic sensor is as follows:
When a 40KHz pulse signal is input from its two pins, it is converted into mechanical vibration energy after being processed by the excitation transducer, and the vibration frequency is about 20kHz or above, thus forming ultrasonic wave. The signal is transmitted to the outer space through the conical “spoke”. When the transmitted ultrasonic signal meets the obstacle, it is reflected back immediately. After receiving the reflected ultrasonic signal, the receiver changes the ultrasonic wave into weak electric oscillation through its internal conversion, and amplifies the signal to obtain the desired control signal. With this signal, various alarm, measurement and automatic control circuits can be controlled.
In the ultrasonic sensor system with separate transmitter and receiver, the resonant frequency of the transmitting sensor should match the anti resonant frequency of the receiving sensor.
2. Basic application mode of ultrasonic sensor
There are three common basic application modes of ultrasonic sensors, as shown in Figure 5-5. Among them: transmission type: suitable for remote control, anti-theft alarm, automatic door, proximity switch, etc.
Separate reflection type: suitable for ranging, liquid level or material level detection.
Reflective type: suitable for material flaw detection, thickness measurement, etc., and can also be used for medical scanning imaging.