User's Guide _______________________________________________________________________
14 ___________________________________________________________________ M210470EN-B
-
Polled mode
:
Transmitter sends a precipitation message whenever requested by
the user.
More information about the precipitation sensor operation modes is
found on page 71.
PTU measurement principle
PTU module contains separate sensors for pressure, temperature, and
humidity measurement.
The measurement principle of the pressure, temperature, and humidity
sensors is based on an advanced RC oscillator and two reference
capacitors against which the capacitance of the sensors is continuously
measured. The microprocessor of the transmitter performs
compensation for the temperature dependency of the pressure and
humidity sensors.
PTU module includes
-
capacitive silicon BAROCAP
®
sensor for pressure measurement
-
capacitive ceramic THERMOCAP
®
sensor for air temperature
measurement and
-
capacitive thin film polymer HUMICAP
®
180 sensor for humidity
measurement.
Heating (Optional)
The heating function keeps the wind and precipitation sensor clean
from snow and ice. The heaters are located below the precipitation
sensor and inside the wind transducers. A temperature sensor
underneath the precipitation sensor monitors the need for heating.
The three fixed temperature limits control the heating power as
follows:
-
temperature (Th) > +3
°
C:
heating is off
-
-2
°
C < temperature (Th) < +3
°
C: 50 % heating power
-
-4
°
C < temperature (Th) < -2
°
C:
100 % heating power
-
temperature (Th) < -4
°
C:
50 % heating power
When the heating function is disabled the heating is off in all
conditions, see the Supervisor message, see page 75 .