A method of calibrating a sensors in a system for obtaining animal data from animals is described. The sensors are configured to obtain measurements of an animal related parameter during arbitrary visits by the animal to the sensors. For at least one of the animals, a first measurement associated with a first sensor of the sensors is obtained, and calculating one or more relations between the first measurement and one or more second measurements associated with the respective animal. Each of the second measurements is obtained using a further sensor, so as to obtain at least one representative relation for each combination of the first sensor and each one of the further sensors. The system calculates, based on the at least one representative relation, a correction factor associated with at least one sensor of the plurality of sensors.