Rain

Rain sensor with light-dependent reset hysteresis, for PLC- or DDC application 

• Article No.

  52 G197 S21 

• Application

  The sensor recognizes rain or snow as precipitation within a few seconds and transmits the report by means of a potential-free relay contact. This switching output can be used for retransmission to e.g. ventilation or shading installations in automatically controlled greenhouses and buildings. Sensitivity settings are not necessary. It recognizes even light drizzles without giving a false rain signal with light condensation.

• Functional description

  If the response threshold is exceeded, the installed fault relay trips immediately. The integrated sensor heating is also fully activated at the same time. The automatic reset delay period begins when the sensor surface has dried (value falls below limit value plus hysteresis). This is controlled using an integrated light sensor that ensures optimum adaptation to the respective weather conditions. In darkness or bad weather the typical reset period increases from approximately 5 minutes to up to 60 minutes. This prevents undesired increases in the temperature under glass, as well as excessively high switching frequencies of the control motors. From the start of the reset delay period until "rain" is reported again, the sensor heating switches down to 25% of its full power. This pre-heating prevents false rain messages due to fog or dew, for example. Additionally: Relay contacts for DDC systems