The current research deal with the design and development of a measurement system to determine the adequate level of pressure applied over a piezoelectric sensor to obtain continuous and non invasive arterial blood pressure values in karate-do athletes during training and competition situations. The paper focus on the characterization of the sensor and the conditioning stage proposed for the continuous acquisition of the signal implementing a cuffless method. The graphic results shows that a relationship between the pressure exerted on the sensor and the different arm`s diameter must be established to validate the measurements.