Sensing is the fundamental function of any medical device for diagnostics and monitoring. Different sensors are used in order to measure physiological parameters describing the functions of the human body. This course aims at providing a solid background on the principles and the technology used for the measurement of some of the most relevant physiological parameters. The main parameters considered in this course are cardiac biopotentials, temperature, and blood flow, volumes, and pressure. The available technology for the measurement of these parameters will be presented and critically discussed. Eventually, the students are expected to become aware of the reasons for choosing a specific sensor and signal conditioning strategy for a specific measurement. To this end, the electronic designs adopted to condition the measured signals and improve the signal-to-noise ratios will be explained together with the measures required to ensure the patient safety. Understanding the limits of the adopted measurement systems will also permit to carry out a critical interpretation of the estimated values.