Ultrasonic sensors have great use in determining the position and dimensions of objects. Their working principle is based on the piezoelectric effect. The piezoelectric effect is the appearance of an electric polarization in a material that strains under stress. By constantly sending an ultrasonic signal and with its reflection, the material is mechanically stressed and generates electrical impulses. In this paper is developed a basic element of ultrasonic system for determining position, consisting of one transmitter and receiver. The transmitted ultrasonic signal is reflected from the receiver and returned to transmitter. Based on the received pulse width, distance from transmitter to receiver is calculated. This paper is based on the use of microcontroller MSP430F2274 and its development tool eZ430-RF2500 from whom is generated a packet of impulses with pause at frequency of 40 kHz to the transmitter. The received signal is amplified, filtered and digitalized. Distance of the transmitter is determined from the data of the signal delay compared to the beginning of the signal transmission. Signal reflections are found by measuring at different linear distances. To determine position, there are placed a minimum of three receivers around the edges of the measurement space and an object within measurement space that has transmitter on. Finally, algorithm is based on the calculation of the intersection of three circulars whose radius are the distances between transmitter and receivers.