The purpose of this research is to detect, locate, and define the blood vessels in the arm of any person who has a problem in taking samples of blood for laboratory testing in order to make it easier, not dangerous nor harmful. Depending on the properties of the scattering wave from the blood and the depth of the penetration, we have calculated the frequency which is necessary to choose the suitable transducer including the Geometric Dimension as well as the materials which is made from (we have taken the 5MHz Doppler –CW for 1.2 cm depth, 2.37 attenuation ratio and the 8MHz Doppler –CW for 0.74 cm depth , with the same attenuation ratio). Depending on the velocity's variation of the blood flow throughout the Biodynamic studies for important arteries in the upper limb, we have found the Doppler frequency which occurs when the acoustic wave passes across the blood red cell. We have designed a suitable electronic instrument which includes the transmitter circuit, receiver circuit, and the output unit - Audio graph.