Application of Ultrasonic transducer in the Industrial Automation

Typical application examples of ultrasonic sensors

Ultrasonic transducer sensors were once considered too difficult or too expensive to operate, but with the reduction in cost and ease of use, more and more mechanical designers have incorporated ultrasonic sensors into the design of machines. Industrial application areas of ultrasonic sensors include detecting filling conditions, detecting reflective objects and substances, controlling the expansion of loop ropes and measuring distances, the following are a few application examples:

In the filling workshop, inspect the bottle

Key points for ultrasonic sensor selection:

Range and size, the size of the detected object will affect the effective range of the ultrasonic range transducer, the sensor must detect a certain level of sound waves to be excited to output signals, a larger object can reflect most of the sound waves to the sensor, so the sensor can The object is sensed within its limits, and a small object can only reflect very few sound waves, thus significantly reducing the sensing range.

The object to be measured, the ideal object that can be detected by the pzt ultrasonic transducers should be a large, flat, high-density object, placed vertically facing the sensing surface of the sensor. Difficult to detect are those whose area A is very small, or are made of sound-absorbing material, such as foam plastic, or have a corner facing the sensor. Some objects that are difficult to detect can be taught to the background surface of the object first, and then respond to the object placed between the sensor and the background.

When used for liquid measurement, the surface of the liquid needs to face the ultrasonic sensor vertically. If the surface of the liquid is very uneven, the response time of the sensor should be adjusted longer. It will average these changes and can compare the fixed reading. Pick. With the improvement of industrial automation level in the world, there are more and more complex applications, which also put forward more and higher requirements for the functions of sensors. In this context, sensors of different types and principles have emerged, and ultrasonic sensors are one of them.

The first thing to explain is what is ultrasonic wave: We all know that sound is produced by vibration. It is a kind of wave, which propagates in other directions in the form of vibration in air or other media. Sound waves of pzt ultrasonic transducers with a frequency between 20Hz and 20kHz cannot be recognized by the human ear. So we call the sound waves with a vibration frequency higher than 20kHz ultrasonic waves. It has the characteristics of high frequency, short wavelength, small diffraction phenomenon, especially good directionality, and directional propagation. Ultrasonic waves will produce significant reflection when they encounter impurities or interfaces to form echoes. Ultrasonic sensors are sensors that convert ultrasonic signals into other energy signals, usually electrical signals.

In principle, ultrasonic sensors can be divided into four categories: ultrasonic measuring sensors, ultrasonic proximity sensors, reflective plate ultrasonic sensors, and through-beam MARPOSS ultrasonic sensors. Among these four types of products, reflective plate ultrasonic and through-beam ultrasonic have the same principle as mirror reflection and through-beam photoelectric in photoelectric sensors, which are very simple and need no further introduction.

Ultrasonic ranging sensor and ultrasonic proximity sensor are the most typical and widely used. Their working principles are the same, except that one output is a switch value and the other is an analog value. The principle is as follows:

Launch mode:

1. The sensor generates a batch of sound waves/pulses under the action of the electronic oscillator, and then these sound waves are sent to the surrounding air.

2. Sound waves are transmitted from the sensor to the target.

3. Switch the sensor to receive mode.

Receive mode:

1. Part of the echo reflected by the object returns to the sensor.

2. The microprocessor of the sensor calculates the time t used for transmission and reception. (If the speed of sound in the medium is v, the distance between the sensor and the target is: S=v*t/2)

3. The microprocessor drives an output signal to display distance or switch value.

In this way, a complete working process is completed, and the principle is also very simple.

Next is the question of application. Although ultrasonic level transducer sensors and photoelectric sensors can replace each other in some applications, most of the time they are actually complementary.

Advantages of ultrasonic sensors over photoelectric sensors:

Can bypass small obstacles (such as dust, photoelectricity is absolutely not allowed in this environment).

Can measure liquid position. (e.g. for liquid level monitoring)

Can measure transparent objects. (such as the presence or absence of glass or displacement information)

Not affected by the color of the surface of the object. (extremely dark or extremely bright surfaces)

Ultrasonic sensors can be used in oily environments. (Even if there is oil splashed on the sensing surface, the sensor can still work normally, but if the oil splashes on the transmitting and receiving surface of the photoelectric sensor, the photoelectric will not work)