Principle of ultrasonic ranging transducer sensor

Publish Time: 2020-06-10 Origin: Site

1 Principle of ultrasonic distance transducer

Ultrasonic sensors are divided into mechanical and electrical types. It is actually a ultrasonic level transducer sensor. It converts electrical or mechanical energy into acoustic energy at the transmitting end, and vice versa at the receiving end. The ultrasonic sensor is designed by using the piezoelectric ultrasonic transducer in the electrical mode, which uses the resonance of the piezoelectric ceramic crystal to work. It has two piezoelectric chips and a resonance plate. When a pulse signal is applied to its poles and its frequency is equal to the natural oscillation frequency of the piezoelectric wafer, the piezoelectric wafer will resonate and drive the resonance plate to vibrate, generating ultrasonic waves. Conversely, if no voltage is applied between the two electrodes, when the resonance plate receives ultrasonic waves, it will press the piezoelectric wafer to vibrate and convert the mechanical energy into electrical signals, which becomes an ultrasonic receiver. In the ultrasonic circuit, a series of pulsed square waves are output from the transmitter. The larger the pulse width, the more the number of outputs, the greater the energy, and the farther the distance can be measured. The structure of the ultrasonic transmitting transducer and the receiving transducer is slightly different, and the marks on the device should be clearly distinguished when it is used.

There are many methods of short range ultrasonic transducer: such as round-trip time detection method, phase detection method, sound wave amplitude detection method. This design uses the round-trip time detection method for distance. The principle is that the ultrasonic sensor emits ultrasonic waves of a certain frequency, propagates through the air medium, and then reflects back after reaching the measurement target or obstacle. After the reflection, the ultrasonic receiver receives the pulse. The time it passes is the the round-trip time and the ultrasonic wave propagation .The distance is related. Test the transmission time to get the distance. Assuming that s is the distance between the measured object and the rangefinder, the measured time is t/s, and the ultrasonic propagation velocity is represented by v/m·s-1, then there is a relationship s=vt／2 (1)

In the case of high accuracy ultrasonic transducer distance requirements, it is necessary to consider the influence of temperature on the ultrasonic propagation speed, and correct the ultrasonic propagation speed according to equation (2) to reduce the error.
v=331.4+0.607T (2) In the formula, T is the actual temperature unit is ℃, v is the propagation speed unit of ultrasonic wave in the medium is m/s.

2 Overall system design plan
The system is composed of hardware circuit parts such as ultrasonic wave transmission, echo signal reception, temperature measurement, display and alarm, power supply, and corresponding software parts. System block diagram.

The entire system is controlled by the single-chip AT89S52. The ultrasonic sensor adopts the split type of receiving and sending transducer, which are respectively an ultrasonic transmitting transducer TCT40-16T and an ultrasonic receiving transducer TCT40-16R. The ultrasonic signal is transmitted into the air through the ultrasonic transmitting transducer, and the echo is received by the ultrasonic receiving transducer after being reflected by the measured object. After the relevant processing, the INT0 pin of the input microcontroller generates an interrupt, calculates the elapsed time, and then calculates the corresponding sound speed according to the specific temperature. According to equation (2), the corresponding distance can be obtained for display. Of course, on some occasions The distance alarm value can also be set as required.

3 Hardware design (This article is collected and organized by Cogo Mall-IC component online procurement platform.

Principle of ultrasonic ranging transducer sensor

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