According to current research, construction of an instrument for measuring a point coordinate in 3D space using ultrasonic waves has not yet been introduced. Measurement of distances by ultrasonic waves with a method similar to the time-of-flight method does not achieve reasonable accuracy because the speed of sound changes with temperature. In this paper, we offer an innovative method that uses a PLL circuit to eliminate the sound speed dependence on temperature in order to measure the speed of sound accurately. Then, the construction of an instrument that measures the coordinate of points in 3D space was explored