The main fields of application of the rotors, type MBA 2.2 and MBA 3.2, are to indicate if storage silos are full, empty or require material. More and more frequently the rugged electromechanical sensors from MBA Instruments GmbH are also used to determine the filling height since they are largely independent of the properties of the charge, as opposed to other limit measuring methods. Level indicators of the series MBA 2.2 for vertical installation and of the series MBA 3.2 as angular arms for horizontal installation are suitable for industrial bulk solids of organic and inorganic materials. Further fields of applications are silos and containers with bulk materials, which also discharge inflammable gases or vapours in addition to explosive dust. The instruments have been approved for use in the dust explosion zone 20 and in the gas explosion zone 1.