The Precipitation Monitor serves as a signal transmitter for determining the start and end of precipitation as well as the duration of precipitation periods, such as those required in meteorological services. The Precipitation Monitor can also be used as a status indicator or signal transmitter for controlling downstream safety devices against precipitation, such as roof windows, ventilation flaps, etc.
Precipitation in the form of spray rain, rain, snow or hail is detected by a light barrier system and triggers a switching signal. With a built-in event filter, the triggering of the switching signal for individual events such as leaves, bird droppings, insects, etc. should be suppressed as far as possible. This requires at least "n" drop events to occur within 50 seconds. The number "n" of drop events (1...15) can be set by DIP switches on the circuit board. After the end of precipitation, the switching signal is reset after an adjustable switch-off delay. By directly evaluating the events, the beginning and end of the precipitation period can be precisely identified. For extreme weather conditions, the precipitation monitor has a heater that prevents snow and ice from accumulating on the surface of the housing. For this purpose, the device is equipped with PTC heating elements, which keep the surface at a temperature of >0°C. The heating elements are mounted on the surface of the device.
The fixture of the device is designed for mounting on a mast tube. During installation, it must be ensured that the precipitation reaches the sensor opening undisturbed and that the device is not exposed to strong shocks or vibrations during subsequent operation.
For the electrical connection the cover with its 5 screws on the underside is unscrewed. The connection terminals and the DIP switches for setting the number of events and release times are then freely accessible. The electrical connection is made according to the wiring diagram. The cables are led from below through the PG glands located in the bottom of the housing and connected to the terminals. After the assembly work, the cover must be screwed tightly to the housing again.
The electrical work must be executed by qualified personnel. The exposed electronics must not be damaged.
The relay output is switched in such a way that "precipitation" is signalled if the supply voltage fails.
Operation without heating
As the precipitation is recorded directly, the device can in principle also be operated without heating. This is easy to do by simply disconnecting it. Attention: Remaining risks under extreme weather conditions due to ice build-up and snow dome formation.
After the electrical connection has been made and the device screwed on, the operating voltage can be switched on. The position of the relay is energized after switching on the operating voltage and signals "no precipitation".
Due to contamination of the atmosphere, a layer of dirt can form on the sensor windows which, however, usually cleans itself through the precipitation. The sensor windows should be checked and, if necessary, cleaned at regular intervals in accordance with the local degree of soiling or environmental pollution.