What Is an Ultrasonic Sensor?

Ultrasonic sensors are sensors that convert ultrasonic signals into other energy signals (usually electrical signals). Ultrasound is a mechanical wave with a vibration frequency higher than 20 kHz. It has the characteristics of high frequency, short wavelength, small diffraction phenomenon, especially good directivity, and can be directional propagation of rays. Ultrasonics have a great ability to penetrate liquids and solids, especially in solids that are not transparent to sunlight. Ultrasonic waves encounter significant reflections on impurities or interfaces to form reflected echoes, and Doppler effects can be produced when they encounter moving objects. Ultrasonic sensors are widely used in industrial, national defense, biomedical and other fields.

Ultrasonic sensor

Ultrasonic sensors are sensors that convert ultrasonic signals into other energy signals (usually electrical signals). Ultrasound is

The core of an ultrasound probe is a piece of plastic or metal

The ultrasonic sensor is mainly composed of the following four parts:

• Transmitter: Generates ultrasonic waves by vibrating a vibrator (usually a ceramic product with a diameter of about 15 mm) and radiates them into the air.

• Receiver: When the vibrator receives the ultrasonic wave, the corresponding mechanical vibration occurs according to the ultrasonic wave, and it is converted into electrical energy as the output of the receiver.

• Control part: by using the integrated circuit to control the ultrasonic transmission of the transmitter, and determine whether the receiver receives the signal (ultrasonic), and the size of the received signal.

• Power supply part: Ultrasonic sensors usually use an external DC power supply with a voltage of DC12V ± 10% or 24V ± 10%, which is supplied to the sensor via an internal voltage regulator circuit.

Depending on the volume, material, and whether the object can be moved, the detection methods used by ultrasonic sensors are different. There are four common detection methods:

• Penetrating: The transmitter and receiver are located on both sides. When the detected object passes between them, according to the ultrasonic

  For ultrasonic sensors

  The basic principle of ultrasonic level measurement is:

  Ultrasonic sensors distinguish

  Difference between ultrasonic sensors and sonar sensors

  Sonar sensors and ultrasonic sensors are two types of detection devices that are often heard. Many people think that these two are a type of sensor. What is the difference between these two types of sensors?
  The sonar sensor directly detects and recognizes the contours of objects in the water and the bottom of the water. The sonar sensor sends out a sound wave signal that is reflected back when it encounters the object

  High-frequency ultrasonic sensor

  Then, calculate its distance and position based on the reflection time and wave pattern. Ultrasound is a mechanical wave with a vibration frequency higher than that of sound waves. It is generated by the transducer chip under the excitation of voltage. It has a high frequency, a short wavelength, and a small diffraction phenomenon. Dissemination and other characteristics. Sonar sensors are mainly used to detect living things, such as detecting which living things are underwater and how big the body is. Often asked what you hear about the device used to detect water monsters is the sonar sensor.
  Ultrasound has a great ability to penetrate liquids and solids, especially in opaque solids, it can penetrate to a depth of tens of meters. Ultrasonic waves encounter significant reflections on the impurities or interfaces to form echoes, and Doppler effects can be produced when they encounter moving objects. Therefore, ultrasonic testing is widely used in industrial, national defense, and biomedical fields. The ultrasonic sensor is a sensor developed using the characteristics of ultrasonic waves. In industry, the typical applications of ultrasonic are nondestructive testing of metals and ultrasonic thickness measurement. The application of ultrasonic sensors in medicine is mainly to diagnose diseases, and it has become an indispensable diagnostic method in clinical medicine.

  Notes on ultrasonic sensors

  1: To ensure reliability and long service life, please do not use the sensor outdoors or in places with a higher temperature ^[2] .

  2: Because the ultrasonic sensor uses air as the transmission medium, when the local temperature is different, the reflection and refraction at the boundary may cause malfunction, and the detection distance will change when the wind blows. Therefore, sensors should not be used near equipment such as forced air fans.

  3: There are multiple frequencies of air jets from jet nozzles, which will affect the sensor and should not be used near the sensor.

  4: Water droplets on the sensor surface shorten the detection distance.

  5: Materials such as fine powder and cotton yarn cannot be detected when absorbing sound (reflection sensor).

  6: Do not use the sensor in vacuum or explosion-proof areas.

  7: Do not use the sensor in areas with steam; the atmosphere in this area is uneven. Temperature gradients will occur, which will cause measurement errors.

  Ultrasonic sensor exposure issues

  The ultrasonic sensor is simple in principle, convenient to use, and low in cost. However, current ultrasonic sensors have some disadvantages, such as reflection problems, noise, and crossover problems.

  Reflection problem

  If the detected object is always at the right angle, the ultrasonic sensor will get the correct angle. Unfortunately, in practice, few detected objects can be detected correctly.

  Several errors may occur:

  Triangle error

  When the measured object is at a certain angle with the sensor, there is a triangular error between the detected distance and the actual distance.

  reflection of mirror

  This problem is the same as the reflection of light learned in high school physics. At a specific angle, the emitted sound wave is reflected by the smooth surface of the mirror, so no echo can be generated, and no distance reading can be produced. At this time, the ultrasonic sensor will ignore the existence of this object.

  Multiple reflections

  This phenomenon is more common when detecting objects at corners or similar structures. The sound wave is received by the sensor after multiple bounces, so the actual detection value is not the actual distance value.

  These problems can be solved by using multiple ultrasonic coils arranged at a certain angle. By detecting the return value of multiple ultrasonic waves, it is used to screen out the correct reading.

  noise

  Although the operating frequency of most ultrasonic sensors is 40-45Khz, which is far higher than the frequency that humans can hear. But the surrounding environment also produces noise of similar frequency. For example, the motor will generate a certain high frequency during the rotation, the high frequency noise generated by the friction of the wheels on a relatively hard ground, the vibration of the robot itself, and even when there are multiple robots, the sound waves emitted by the ultrasonic sensors of other robots These will cause the sensor to receive the wrong signal.

  This problem can be solved by encoding the transmitted ultrasonic waves, such as transmitting a set of sound waves of different lengths, and the distance calculation is performed only when the probe detects the same combination of sound waves. This can effectively avoid misreading caused by environmental noise.

  Cross problem

  The crossover problem is caused when multiple ultrasonic sensors are mounted on the robot at an angle. The sound waves emitted by the ultrasonic wave X are reflected by the mirror and obtained by the sensors Z and Y. At this time, Z and Y will calculate the distance value based on this signal, so that the correct measurement cannot be obtained.

  The solution is to encode the signal from each sensor. Let each ultrasonic sensor only listen to its own voice.