disadvantages and solution of ultrasonic transducer(一)
1.Blind spot of the measurement.blind spots of accurate compact ultrasonic transducer measurement is caused by two factors: firstly, after the ultrasonic sensor transmit signal, the transducers exist residual vibration, if the signal is emitted ,immediately opening the receiving circuit, the residual signal can cause misjudgment. Generally ,after launching signal, which delays a period of time and then open the receiving circuit, it can not detect the propagation distance of ultrasound during this time, so there will be measurement of the blind area.The strength of ultrasonic residual signal is related to the performance of the transducer and the strength of the transmitting signal. By increasing the performance of the transducer and reducing the power of the transmitted signal, it can reduce the residual vibration and the dead zone. The second is the integrated type of the ultrasonic depth sensor requires the controller to switch the transmission and reception of circuit, interval of switching time will also produce a blind spot. You can use a higher frequency of the controller and faster switching circuit to reduce blind spots. In addition to improving the performance of the controller and the sensor itself, the scientists use infrared sensors without blind spots, high precision, strong direction, but impacted by environment larger ,closer to detection distance ,combination of ultrasonic sensors and infrared sensors to achieve complementary advantages, to overcome the problem of ultrasonic sensors.of dead zone.
Ultrasonic propagation velocity is affected by environmental changes. The speed of ultrasonic propagation in the medium is affected by environmental changes (such as temperature, pressure, humidity, etc.), the temperature is the most obvious impact factor. in general,temperature is increasing 1 ℃ each time, the speed of sound is increasing by about 0.6m / s, in order to improve the measurement accuracy of ultrasound transducer for depth gauge, the sound velocity must be corrected. The main methods of sound velocity correction are temperature compensation method and set correction method. Temperature compensation method uses the temperature sensor to detect the ambient temperature, and then calculate the corresponding speed of sound. Setting the correction method is using dual-channel measurement during the distance measurement: a channel through the known distance of the reference to determine the current environment and sound velocity; the other channel is measured by the speed of sound prevail, In the normal way, to avoid the impact of environmental changes . Scientists use the correction method to compensate the speed of sound, measuring the liquid level, to achieve a more accurate of measurement than the temperature compensation method .