disadvantages and solution of ultrasonic transducer(二)
volume of obstacle can not be too small. According to the theory of ultrasonic propagation, when the size of obstacle is less than 1/2 of the length ofultrasonic transducer wave, the ultrasonic wave will diffuse; when the size of obstacle is bigger than 1/2 of the wave length, it can be reflected. For example, the use of ultrasonic sensors that transmit frequency is 40kHz, corresponding length of half-wave is 0.025mm, so theoretically the smallest side length can be measured is 0.025mm.Improving transmission frequency of ultrasonic wave can be realized to the smaller size obstacle.
Measurement distance is limited. The amplitude of the ultrasonic echo signal expands exponentially with the propagation ultrasonic range finder distance, so that the echo signal received by the receiver decreases greatly with the measurement distance, resulting in a limited distance measurement . While increasing the transmit power of the transmitter will increase the residual vibration of the transducer and increase the measurement of dead zone. automatic gain adjustment (AGV) is stringed in the circuit , the magnification times of circuit increases along with the measurement distance,which reduce the affect of measurement of blind zone.But duo to the ultrasonic transmission power and loss of restrictions,currently, domestic maximum measurement distance of ultrasonic sensor is generally not more than 15m. development trend of ultrasonic sensor is as for a typical non-contact detection technology, at the same time ,it owns small size, low cost, free from electromagnetic, light, smoke and other interference advantages, which has broad prospects for development.