distance ultrasonic wave

The pulse reflection mode ultrasonic equipment is used for robot technology, safety and control system of transportation tool, object recognition system and other distance distance measuring equipment. The sensor provides high resolution in the direction of the target and determines the distance to the object by measuring the time from the launch to the receiving. Unlike piezoelectric ceramics and electrostatic induction devices, piezoelectric thin films can emit very short pulses (because they have lower quality factor), making the same device not only be used as a transmitter, but also as a receiver, even near the sensor.

It is easy to make a plurality of piezoelectric thin film units, such as figure 62. It is possible to control the directional pattern and sound characteristics by designing the geometric shapes of these cylindrical units (length, radius, number of units). A sensor with a working frequency of 40~200KHz has been made. The ElotechGmbH report indicates that when the sensor is 1 meters, the average sensitivity of sensors is 0.2~1mV/Pa in the receiving mode, and the emission mode is 20~50mPa/V when the noise is less than 1uV. The minimum measurement distance in the pulse reflection mode is 30 millimeters. The width of the main beam is less than 10 degrees.

The biggest single lobe amplitude decreased at 60KHz when 12Db

Measure the distance of 15 meters. Single and multiple cell sensors

An example of the directional pattern is shown in Figure 63.

Multiple units can also be used to scan objects without moving sensors. Each unit in the sensor can be activated in order, just like an ultrasonic array.

The applications of these ultrasonic air range units include alarm equipment for trucks and farm machinery transportation safety systems, and monitoring systems for highway traffic density. Another extreme application of piezoelectric thin film sensor arrays is to measure the gap size of the modern aircraft frame structure to improve the coordination between layers. The piezoelectric thin film array has been made and tested to detect air gaps, with a resolution of up to 25um at a thickness of up to 5cm. The operating frequency of these emitter and receiving unit on the 2.5cm center 30X30cm array is 3.5MHz.

sound

speaker

One of the earliest applications of piezoelectric films is the high frequency loudspeakers (Figure 64) and headphones developed by avant-garde electronics. Because of the improvement in electrode reliability and lead connection and packaging technology, there is a more intense interest in these applications. GalloAcoustics developed a high fidelity omnidirectional high frequency loudspeaker with a 52um thick piezoelectric thin film cylinder. The high frequency loudspeaker attenuates below 2kHz. The characteristics are as follows:

At high frequency, the divergence angle of the horizontal direction is 330 degrees, which is 10 times that of the conventional high frequency loudspeaker.

A very wide range of dynamics.

Linear frequency response

Fast input pulse response, which truly reproduces the high frequency part.

A new type of high frequency loudspeaker has been developed. These devices take advantage of the thin, light and uniform natural characteristics of the piezoelectric thin films. Examples include speakers for blowing parts, such as balloons and blowing toys, clothing loudspeakers (including headphones), and thin film speakers for magazine advertisements, greeting cards and mailing products.

Microphone

A high quality microphone is made by fixing the piezoelectric film on the retaining ring or on a chassis hole. Used in the design of the supporting the piezoelectric film axis deviated slightly, foam cushion, small pillar, strip or similar structure of the piezoelectric film with slight curvature radi