Abstract: A controlling method using an ultrasonic sensor is provided. Firstly, a first ringing time of the ultrasonic sensor is set when the ultrasonic sensor is in a standby status. Then, a sensing wave is transmitted, and a second ringing time is detected. Then, the second ringing time is compared with the first ringing time. If the second ringing time is not equal to the first ringing time, a function control signal is generated.

Abstract: A signal decay time adjusting method is used in an ultrasonic transducer. Firstly, a first driving signal is generated by a pre-processing module. When the first driving signal is received, an ultrasonic transmitting/receiving module generates vibration and transmits a sensing wave according to the first driving signal. Then, the pre-processing module stops generating the first driving signal so that the vibration generated within the ultrasonic transmitting/receiving module is decayed as a decay signal. Then, a second driving signal is generated by the pre-processing module according to the first driving signal, and the second driving signal is transmitted to the ultrasonic transmitting/receiving module. When the second driving signal is received, the decay signal is offset according to the second driving signal, so that a decay time of the decay signal is shortened. When the sensing wave is reflected by an object, a reflective wave is received by the ultrasonic transmitting/receiving module.