A measuring system for monitoring a planetary gear train having a plurality of planetary gear stages, each planetary gear train including a sun shaft, a ring gear, a planet gear connected to the sun shaft and ring gear, and a planet carrier rotationally connected to the planet gear, said measuring system comprising:
- a sensor arranged on the planet carrier of a selected one of the planetary gear stages for detecting a variable of the planet gear;
- and
- an electronic power supply operably connected to the first sensor for supply of the sensor with electrical energy.