Increasing loads, aging, new construction materials like CFRP (carbon fiber reinforced polymers) and also cost pressure are influences for fitness of traffic infrastructures, especially bridges. Prolonged health monitoring can be a means to compete with these challenges. The lifetime of infrastructure can reach 100 years, while that of sensors is typically much shorter. Therefore, sensors need to be long-term qualified and might have to be replaced by new sensors or even another sensor system during the life cycle of a structure. A reliable system for data acquisition and data analysis will be essential: Do the measurement data really relate to the monitored infrastructure and are not an effect of the degradation of the sensing system? We discuss measurement uncertainty and reliability of data obtained by different sensor types, including resistance strain gages, fiber optical sensors and other sensors systems which are in service up to 17 years. Keywords Long-term Á Health monitoring Á Infrastructure Á Reliability Á Carbon fiber reinforced polymers (CFRP) Á Fiber optical sensor (FOS) Á Fiber bragg grating (FBG) Á Resistance strain gages (RSG) Á Sensor Á Data acquisition