System for measuring the stress/tension in the concrete foundation of wind turbines Delivery of a system for measurement of compressive stress and stress / strain or tensile stress in concrete for foundations of wind turbines. Technical implementation in accordance with the system. The foundation is a data logger for 32 channels RS485, sensors for compressive stress and tensile stress sensors are supplied. Each sensor has an own temperature sensor and a sensor ID in the ROM without own electronics for the measurement of the TOF. The sensor cable is connected to a 16 -channel multiplexer. Each multiplexer includes electronics for measuring the TOF. Each multiplexer has its own electronics unit in die-cast aluminum housing. The data output is a digital output RS485. Sensor ID, channel number, temperature 12 Bit, TOF in ps resolution. The data is stored in a data logger on SD card. The data can be read via USB. On the RS485 bus more arbitrary devices can be connected. The real-time data can with a computer program in any physical units, such as stress, strain, load or elongation be converted .