Patent attributes
The present invention is intended to provide an ultrasonic range finder to measure a distance quickly and precisely under different environments. The ultrasonic range finder comprises a casing, an ultrasonic transmitting/receiving unit, a signal processing circuit connected electrically with the ultrasonic transmitting/receiving unit in the casing, a group of operation buttons on the casing and a display unit. The ultrasonic range finder further comprises a calibration rod to provide a constant reference distance. The calibration rod includes a first end connected to the casing. The calibration rod further includes a second end extendable outwardly relative to the casing and a body between the first and the second ends. By measuring a propagation time of an ultrasonic signal within the constant reference distance an ultrasonic propagation speed can be determined quickly and precisely and thereby perform the distance measurement quickly and precisely without being affected by changes in the environment.
