The compressed seal on the cover prevents leakage of dry deposition in to the container and retards evaporation. Underside of cover is protected from ground splash when the cover is opened. Splash shield covers, but does not touch the seal. System reliability is essential for collection of valid samples. Cover drive motor is rated for 35 years typical service.
All parts are easy to replace without special tools.
Battery back up can be provided to assure operation if line power fails.