Page 83 - Advanced Course

KNX ADVANCED COURSE

6.2.4 Precipitation sensor

A precipitation sensor - also known as rain sensor - senses the precipitation and transmits
the value to the bus for further processing. This sensor can be used in conjunction with
blind actuators to prevent canvas of sun shading from getting wet and destroyed or even
with an irrigation system to switch it off for saving water.

Figure 61: A common rain sensor

The precipitation detection is usually transmitted using a 1 bit Group Object. Since there is
no standard Datapoint type for rain indication, the 1.005, DPT_Alarm is used.

Figure 62: A typical Group Object in ETS for reading the detection of precipitation

6.2.5 Solar radiation sensor

The solar radiation sensor measures the sun intensity as amount of heat.
The current radiation is measured in watts per square metre and the most common use is
to calculate the energy input to an area, especially for installed solar panels. With this, it is
possible to calculate and use the produced energy during a defined period of time.
There are two different types of solar radiation sensors; the ‘Compact sensor’, which is a
compact device including the sensor in its housing and the ‘Modular Sensor’, which is a
sensor unit, either for DIN rail or wall mounting, with an external probe.

Figure 63: A compact solar radiation sensor and a classical sensor with external probe

Home and Building Management Systems KNX Association
HVAC Control with KNX HVAC_E0813b.doc Page 57/60