Ultrasonic sensors use high frequency acoustic signals to detect the presence of the target. They consist of an ultrasonic capsule, an excitation circuit, a detection circuit and an output circuit. There are three operating modes:
Direct diffusion: the ultrasonic capsule is excited by high voltage pulses to the point that it begins to emit an ultrasonic signal. The signal is reflected by the target towards the sensor and the detection circuit measures the time between the moment of emission and that of reception. it is thus possible to detect both the presence of the object and the distance from the sensor. This system has a "blind zone" in front of the sensor where detection is not possible or reliable, which varies depending on the capsule used.
Retro reflection: it needs a background to work. The detector measures the time taken by the ultrasonic signal to be received by the sensor once reflected from the background. Any variation of this measure indicates the presence of the object. The detection can take place in the whole work area, even in contact with the sensor.
Projector and receiver: the system consists of two independent parts, an emitter and a receiver. The receiver receives the ultrasound beam emitted by the emitter, a variation of the beam indicates the presence of the object.
Ultrasonic sensors detect almost all types of material. The actual detection distance depends on the size of the target and the type of material to be detected. Factors to consider are the shape of the object and the temperature of the object.
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