Kipp & Zonen LAS, Instruction Manual

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8
i.e. L
v
E is the residual term of the energy balance. Both the LAS-BET and the LAS-RET system
provide L
v
E according to the latter step.
Although the
LAS-BET and LAS-RET provide the same output ( H and L
v
E ) they differ in complexity
and flexibility. The LAS-BET comprises a LAS (or a XLAS ), a number of meteorological sensors
(tower and arms are optional), a data logger and a software package. The data logger collects the
output from all sensors including the
LAS / XLAS . Signal cables limit the distance between the data
logger and the sensors meaning that the LAS / XLAS receiver and the sensors must be roughly
located at the same site as the data logger.
LAS-Transmitter LAS-Receiver
Datalogger (Master)
U
Cn2
and U
demod
RF Modem 2
RF Modem 1
U
Cn2
and U
demod
Wireless RF
communication
LAS-system
Meteorological tower and sensors:
Computer with PCMCIA card reader and EVATION
software
Datalogger (Slave)
Field station
U
Cn2
,U
demod
and meteorol. data
(2 Mb Flash card or RS-232)
Net radiation
Soil heat flux
Temperature / humidity
Wind speed / direction
RS-485
RS-485
Wireless RF
communication
Figure 1: Schematic overview of the LAS-RET system. This system consists of a LAS / XLAS
scintillometer, which is measured by a COMBILOG data logger (
SLAVE ). Using two RF radio modems the
data from the LAS (U
Cn2
and U
demod
) is transmitted to the central COMBILOG data logger ( MASTER )
located at the weather station. Here all measured data is stored on a 2 Mb flash card. Once the data of the
Flash card has been stored on a computer the EVATION software processes the data to fluxes of sensible
heat and evaporation. The weather station comprises a 4 m tower and a number of sensors.
In order to improve the flexibility of installation, especially the site selection of the
LAS / XLAS and the
meteorological tower, the LAS-RET system is equipped with a 2.4 GHz RF link. The RF link transmits
the signal output from the LAS / XLAS receiver to the main data logger of the meteorological station.