Michael Kania, GER
Section 10 - 5.2.1 Measurement
5.2.1 Weighing equipment. The scales used to establish the weight of an aircraft entering a competition, shall have an accuracy of not less than 0,2% when weighing up to 472.5 kg. The calibration of the scales shall have taken place within a year from the date of the weighing. All scales used shall carry a certificate indicating weighing accuracy and the time of the latest calibration of the scales. For records it is sufficient that the weighing rules of the airworthiness certifying body, of the country where the aircraft is registered, are followed.
In the near future we probably have to weigh microlight aircrafts with a weight of up to 600 kg.