Kipp & Zonen LAS User manual

Instruction Manual
Large Aperture Scintillometer
LAS

1
IMPORTANT USER INFORMATION
Reading this entire manual is essential for full
understanding of the proper use and safe operation of this product
Should you have any comments on this manual we will be pleased to receive them at:
Kipp & Zonen B.V.
Delftechpark 36
2628 XH Delft Holland
P.O. Box 507 2600 AM Delft Holland
Phone [phone]
Fax [phone]
Email [email protected]
Web www.kippzonen.com
Kipp & Zonen reserves the right to make changes to the specifications without prior notice.
WARRANTY AND LIABILITY
Kipp & Zonen guarantees that the product delivered has been thoroughly tested to ensure that it
meets its published specifications. The warranty included in the conditions of delivery is valid only if
the product has been installed and used according to the instructions supplied by Kipp & Zonen.
Kipp & Zonen shall in no event be liable for incidental or consequential damages, including without
limitation, lost profits, loss of income, loss of business opportunities, loss of use and other related
exposures, however caused, arising from the faulty and incorrect use of the product. User made
modifications can affect the validity of the CE declaration.
COPYRIGHT© 2006 KIPP & ZONEN
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or
transmitted in any form or by any means, without permission in written form from the company.
Manual version: 0706

2
Throughout the manual symbols are used to indicate to the user important information. The meaning
of these symbols is as follows:
The exclamation mark within an equilateral triangle is intended to alert the user to the
presence of important operating, maintenance and safety information

3
TABLE OF CONTENTS
IMPORTANT USER INFORMATION.......................................................................................1
WARRANTY AND LIABILITY .............................................................................................................. 1
COPYRIGHT© 2006 KIPP & ZONEN.................................................................................................. 1
TABLE OF CONTENTS...........................................................................................................3
LIST OF SYMBOLS.................................................................................................................5
SYMBOLS............................................................................................................................................ 5
ABBREVIATIONS ................................................................................................................................ 6
1. GENERAL INFORMATION .................................................................................................7
1.1 INTRODUCTION TO LAS-BET AND LAS-RET SYSTEMS .......................................................... 7
1.2 MANUAL ...................................................................................................................................... 10
2. TECHNICAL DATA............................................................................................................11
2.1 LAS / XLAS .................................................................................................................................. 11
2.2 WEATHER STATION AND SENSORS....................................................................................... 11
2.3 RF TELEMETRY LINK................................................................................................................. 12
3. INSTALLATION AND SET-UP ..........................................................................................13
3.1 DELIVERY ................................................................................................................................... 13
3.2 STEP BY STEP INSTALLATION PROCEDURE ........................................................................ 15
3.2.1 Site selection ......................................................................................................................... 15
3.2.2 Installing LAS / XLAS ............................................................................................................ 16
3.2.3 Power supply LAS / XLAS..................................................................................................... 16
3.2.4 Installing weather station....................................................................................................... 18
3.2.4.1 Site selection .................................................................................................................. 18
3.2.4.2 Installation of mast and mounting of sensors ................................................................. 19
3.2.4.3 Mounting enclosure, solar panel and connecting wires ................................................. 24
4. SOFTWARE.......................................................................................................................29
4.1 COMBILOG SUPPORT SOFTWARE.......................................................................................... 29
4.1.1 Setting communication parameters....................................................................................... 29
4.1.2 Original COMBILOG module settings and programs............................................................ 31
4.2 PCI-SWAP-BOX SOFTWARE..................................................................................................... 33
4.3 PCMCIA FLASH MEMORY CARD SOFTWARE (CardWare) .................................................... 34
4.3.1 Installing CardWare software ................................................................................................ 34
4.3.2 Reading PCMCIA Flash Memory Cards ............................................................................... 34
4.4 EVATION DATA PROCESSING SOFTWARE............................................................................ 35
4.4.1 Installing EVATION ............................................................................................................... 35
4.4.2 Installing Modified Algorithms ............................................................................................... 36
4.4.3 Getting started....................................................................................................................... 37
5. OPERATION ......................................................................................................................39
5.1 REAL-TIME MONITORING OF MEASUREMENTS.................................................................... 39
5.1.1 Via COMBILOG support software ......................................................................................... 39
5.1.2 Via display of COMBILOG .................................................................................................... 41
5.2 CALIBRATION COEFFICIENTS ................................................................................................. 41
5.3 DATA FILES ................................................................................................................................ 42
6. MAINTENANCE.................................................................................................................43
7. TROUBLE SHOOTING......................................................................................................45

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APPENDIX 1 – TESTING RF TELEMETRY LINK ................................................................46
APPENDIX 2 – DIP SWITCH SETTINGS RF MODEM .........................................................49
APPENDIX 3 – MOUNTING ANTENNAS .............................................................................51
APPENDIX 4 – SERIAL PORT CONNECTIONS ..................................................................53
APPENDIX 5 – INSTALLATION FORM ................................................................................55
APPENDIX 6 – INSPECTION PROCEDURE ........................................................................59
APPENDIX 7 – SETTING DATE / TIME COMBILOG ...........................................................65
APPENDIX 8 – FORMAT PCMCIA FLASH MEMORY CARDS ...........................................69
APPENDIX 9 – CONNECTION PLAN LAS-BET & LAS-RET ..............................................70

5
LIST OF SYMBOLS
SYMBOLS
Cn
2structure parameter of the refractive index of air [m-2/3] (
() 12
22
10 − =CN
U
n
C)
CT
2structure parameter of temperature [K2m-2/3]
CQ
2structure parameter of humidity [kg2m-6 m-2/3]
dzero-displacement height [m]
Daperture diameter of receiver and transmitter unit [m]
fTuniversal stability function [-]
ggravitational acceleration [∼9.81 m s-2]
Gssoil heat flux [W m-2]
G1, HFP1soil heat flux plate 1 [W m-2]
G2, HFP2soil heat flux plate 2 [W m-2]
Hsensible heat flux [W m-2]
Lpath length [m]
Lvlatent heat of vaporization [~2.45 ×106J kg-1 @ 20 oC]
LvElatent heat flux (or evaporation ET) [W m-2] [mm day-1]
(conversion [W m-2] ↔[mm day-1]: 1 W m-2 = Lv/86400 ≅0.0353 mm day-1)
LMO Obukhov length [m]
Pot potentiometer path length setting at Path length knob [-]
Pair pressure [Pa]
Press air pressure [hPa]
(conversion [Pa] ↔[hPa]: 1 hPa = 100 Pa = 1 mbar)
PUCN2 scaled Cn
2[m-2/3] (Cn 2= PUCN2⋅10-15)
Qabsolute humidity [kg m-3]
Q* net radiation [W m-2]
Rdspecific gas constant for dry air [∼287 J K-1 kg-1]
RH relative humidity [%]
Rnnet radiation [W m-2]
Rvspecific gas constant for water vapour [∼461.5 J K-1 kg-1]
Tabsolute air temperature [K]
T+ air temperature upper level [oC]
T- air temperature lower level [oC][
(conversion K [Kelvin] ↔oC [Celsius]: ×oC = ×+ 273.15 K)
T*temperature scale [K]
uwind speed [m s-1]
u*friction velocity [m s-1]
UCN2 log Cn
2signal [V] (
(
) 12
22
10 − =CN
U
n
C) [-5 V to 0 V]
UDEMOD demodulated signal [V] (UDEMOD = I) [-1 V to 0 V]
WD wind direction [o]
zLAS (effective) height LAS or XLAS [m]
z0aerodynamic roughness length [m]
zuheight wind speed measurements [m]

6
β Bowen ratio [-] ( β = H/LvE)
λwavelength of EM radiation (880 nm) [m]
ρ density of air [kg m-3] [∼1.2 kg m-3 (at sea level (1013 hPa)!)]
2
σ variance
2
ln I
σ of natural logarithm of intensity fluctuations ( ln(I) ) [-]
22
IUDEMOD
σσ =of UDEMOD or intensity I[V2]
2
2CN
U
σ of UCN2 [V2]
ABBREVIATIONS
BET Basic Evapo-Transpiration system
(X)LAS (eXtra) Large Aperture Scintillometer
MOST Monin-Obukhov Similarity Theory
A relationship describing the vertical behavior of non-dimensionalized mean
flow and turbulence properties within the Surface Layer as a function of the
Monin–Obukhov key parameters.
PBL Planetary Boundary Layer
The PBL is the lowest region of the troposphere, which is directly affected by
heating and cooling of the earth surface. In general the depth of the PBL
varies between 100m to 2000m. The depth of the PBL increases during the
day, when the surface is heated by the sun and decreases during the night
due to radiative cooling.
RET Radio Evapo-Transpiration system
RS Roughness Sublayer
Lowest part of the SL, where the flow is influenced by individual roughness
elements. Consequently, the SL can be divided into the Constant Flux Layer
and the Roughness Sublayer. The height of the Roughness Sublayer strongly
depends on the height (size and form) of the roughness elements, but also on
the distribution. Usually, over tall vegetation 3 times the obstacle height is
taken as the height of the Roughness Sublayer.
SL Surface Layer
In general in the lowest 10% of the PBL the surface fluxes are constant with
height, this part of the PBL is also known as the Constant Flux Layer or
Surface Layer (SL). Therefore fluxes measured in the SL can be considered
as being representative fluxes for the heat and mass exchange processes
between the atmosphere and the surface. In general the SL varies between
20m to 100m and like the PBL increases during the day and decreases again
during the night.

7
1. GENERAL INFORMATION
1.1 INTRODUCTION TO LAS-BET AND LAS-RET SYSTEMS
The LAS-BET and LAS-RET (ET stands for evapotranspiration) systems are scintillometer based
surface flux monitoring systems, specially intended for earth energy balance and water management
studies. Evapo-transpiration is an important term of the surface energy budget
sv GELHQ ++=
*[W m-2], (1)
where Q*(or Rn) is the available energy known as the net radiation, Hthe sensible heat flux, LvEthe
latent heat flux and Gsthe soil heat flux. In some cases extra storage and/or advective terms can be
added to the surface energy balance. The evapo-transpiration (ET), which stands for the evaporation
(E) from bare soil and the transpiration (T) by vegetation, is linked to the latent heat flux (LvE) as
follows
v
v
L
EL
ET =, (2)
where Lvis the latent heat of vaporisation (the energy required to evaporate 1 kg of water, Lv∼2.45 ×
106J kg-1). This means that ET can be expressed as an energy flux (LvEin [W m-2], mostly used in
used in meteorology) or as a mass flux (ET in [mm day-1], mostly used in hydrology). Approximately 1
W m-2 is equal to 0.0353 mm day-1. The latent heat flux or ET is an important term of the soil water
balance
outputinput −=∆S, (3)
where ∆Sis the change of storage of water in the soil, which is the result of the amount of input into
the soil (e.g. due to rainfall or irrigation) minus the amount of loss of water (e.g. due to
evapotranspiration, surface-runoff or drainage).
The LAS-BET and LAS-RET have been developed to provide area-representative surface fluxes of
sensible heat (H) and latent heat (LvE). Most unique feature of the both systems is the line of sight
path-integrating capabilities of the (eXtra) Large Aperture Scintillometer (LAS / XLAS). This allows the
user to measure area-averaged surface fluxes of sensible heat at scales of 0.2 to 8 km, over both
homogenous and moderate heterogeneous areas. So far most traditional measurement techniques
(e.g. Eddy-Covariance method, Flux-Profile method, Bowen-ratio method and Lysimeters) are actually
point (in-situ) measurements and therefore less representative for large (natural and therefore
heterogeneous) areas.
Basically, the LAS-BET and LAS-RET system consist of two parts, namely a scintillometer (LAS or a
XLAS) and a weather station (developed by Theodor Friedrichs & Co). The structure parameter (Cn
2)
measured by the LAS / XLAS and additional meteorological data (air temperature at 2 levels, wind
speed and air pressure) collected by the weather station are used to determine the surface flux of
sensible heat H. By adding a net radiometer and soil heat flux sensors, the latent heat flux can be
derived, via
sv GHQEL −−= *, (4)

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i.e. LvEis the residual term of the energy balance. Both the LAS-BET and the LAS-RET system
provide LvEaccording to the latter step.
Although the LAS-BET and LAS-RET provide the same output (Hand LvE) 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)
UCn2
and Udemod
RF Modem 2
RF Modem 1
UCn2 and Udemod
Wireless RF
communication
LAS-system
Meteorological tower and sensors:
Computer with PCMCIA card reader and EVATION
software
Datalogger (Slave)
Field station
UCn2 ,Udem od and meteorol. data
(2 Mb Flash card or RS-232)
Net radiation
Soil heat flux
Tem perature / 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 (UCn2 and Udemod) 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.

9
This station comprises sensors, a mast with cross arms and cable guys, a data logger and a power
supply (battery and solar panel). In this way the user is able to place the meteorological station up to
5km away from the LAS / XLAS receiver, preferably near the centre of the path of the LAS / XLAS or
at another representative spot. The RF telemetry link operates at 2.4 GHz, which is license free
globally1. Extra advantage: all data including the signals of the LAS / XLAS are stored centrally at the
meteorological tower on a 2Mb PCMCIA flash card.
The data processing of the LAS-BET and LAS-RET systems is done by a software program, called
EVATION (stands for evapotranspiration). This user-friendly program, developed by Kipp & Zonen,
processes the data to (daily) fluxes of sensible and latent heat. In Figure 1 an overview is shown of the
LAS-RET system. Figure 2 shows the LAS-BET system (without the RF telemetry link).
LAS-Transmitter LAS-Receiver
Datalogger (Master)
UCn2 and Udemod
LAS-system
Meteorological sensors:
Computer with PCMCIA card reader and EVATION
software
Net radiation
Soil heat flux
Tem perature / humidity
Wind speed / direction
UCn2 ,Udemod and meteorol. data
(2 Mb Flash card or RS-232)
Figure 2: Schematic overview of the LAS-BET system. This system consists of a LAS / XLAS
scintillometer and a number of meteorological sensors. All sensors (including the LAS) are measured by
1 COMBILOG data logger. The 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.
1Optional license free bands are: 915 MHz (US & Canada) and 922 MHz (Australia & Israel)

10
Some LAS-BET and LAS-RET features are:
•Area-representative fluxes of sensible heat and (actual) evaporation (scale 0.2 km to 8 km 2)
•RF telemetry link between LAS / XLAS receiver and weather station3. Advantages of the RF
link: the site selection of the weather station with respect to the LAS / XLAS is more flexible;
ALL data is centrally stored at one location (PCMCIA flash fard).
•(Optional) Switching power supplies with universal AC input and backup batteries provide
continuous operation in areas that have occasional net power drops.
•Solar battery powered weather station for flexible site selection2.
•Easy downloading of data using 2 Mb PCMCIA flash cards.
Some features of EVATION:
•Runs on Windows 98/NT/2000/ME/XP platforms
•User-friendly but offers also special tools for experts
•Handles multiple LAS-BET and/or LAS-RET set-ups
•Uses research-grade processing algorithms
•Handles multiple processing algorithms4
•Built-in effective LAS / XLAS height calculator
•Data and flux averaging to daily means (e.g. ET in [mm day-1])
•Configurable output allows analysis of wide range of meteorological quantities (i.e. turbulent
surface fluxes, atmospheric stability, structure parameters)
•Automatic organizing of data files
1.2 MANUAL
This instruction manual is intended for customers who have purchased the LAS-BET or LAS-RET
system. It includes all the main information necessary to properly install and operate the systems.
More detailed information such as the operating specifications of a specific sensor/instrument can be
found in the separate delivered manuals.
2Depending on atmospheric conditions
3Applies to LAS-RET system only
4Depending on LAS-BET / LAS-RET configuration

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2. TECHNICAL DATA
2.1 LAS / XLAS
The operating specifications of the LAS / XLAS can be found in the LAS instruction manual.
2.2 WEATHER STATION AND SENSORS
Table 1: Operating specifications of sensors. For detailed information see manuals of supplied sensors.
Note that the LAS-BET and LAS-RET system are not supplied with a relative humidity sensor. Instead a
default value is used of 50%.
COMBILOG 1020 Data logger
Operating temperature -30 oC to +60 oC
Voltage and power Nominal 12 VDC (~ 40 mA)
Analogue inputs 8 (16-bit)
Digital I/O 6
Interfaces RS-232/RS-485
Data storage - 256 kb internal RAM
- PCMCIA Flash Memory Card (2Mb)
Temperature sensor
Range -40
oC to +60 oC
Output PT100 (4-wire)
Calibration Sensors are individually calibrated between
-20oC to 50oC with an accuracy of 0.01oC @ 0oC
Wind speed sensor
Operating temperature -25 oC to +80 oC
Range 0 – 60 m s-1
Voltage and power sensor
Voltage and power heater
Nominal 12 VDC (~2 mA)
Nominal 12 VDC (max 7 Watt)
Output Digital: 0 – 600 Hz (corresp.; 0 – 60 m s-1)
Wind direction sensor
Operating temperature -25 oC to +80 oC
Range 0 – 360o
Voltage and power sensor
Voltage and power heater
Nominal 12 VDC (~2 mA)
Nominal 12 VDC (max 7 Watt)
Output 8-bit Gray Code
Air pressure sensor
Operating temperature -25 oC to +70 oC
Range 600 – 1050 hPa
Voltage and power Nominal 12 VDC (~10 mA)
Output 0.3 – 4.9 VDC
Net radiation sensor (Kipp &
Zonen NR-Lite)
Operating temperature -30 oC to +70 oC
Range ±2500 W m-2
Output ±25 mV
Soil heat flux sensor
Operating temperature -30 oC to +70 oC
Range ±2000 W m-2
Output ±20 mV
Kipp & Zonen reserves the right to make changes to the specifications without prior notice.

12
The LAS-BET and LAS-RET systems are not supplied with a relative humidity sensor. Instead a
default value is used (50%). Note that the uncertainties in RH have little effect on the sensible heat
flux and the evapotranspiration.
2.3 RF TELEMETRY LINK
Table 2: Operating specifications RF telemetry and antenna.
RF Modem 2.4 GHz (X24-019PKI-R)
Manufacturer MaxStream
(www.maxstream.net)
Operating
temperature
-40 oC to +85 oC
Frequency 2.4000-2.4835 GHz
(World wide license free)
Spread spectrum
type
Frequency hopping, Wide band
FM modulator
Interface RS-232/RS-485/RS-422
Voltage Nominal 12 VDC
Power ~200 mA (mode dependant)
Serial data
throughout
19.2 kbps
RF baud rate 20 kbps
Transmit power
output
50 mW (17 dBm)
Receiver sensitivity -102 dBm
Antenna
Operating
temperature
-45 oC to +70 oC
Frequency 2.4000 – 2.4835 GHz
Type Vagi (directional)
Gain 16 dBi
Impedance 50 Ohm
Range ∼5 km
Kipp & Zonen reserves the right to make changes to the specifications without prior notice.

13
3. INSTALLATION AND SET-UP
3.1 DELIVERY
In general the delivery of the LAS-BET and LAS-RET includes the following items5:
Scintillometer part:
LAS-BET LAS-RET
BET = Basic Evapo-Transpiration system
Flux station for measuring fluxes at field scale
LAS or XLAS scintillometer
•Telescopes
•2×5 m cable
•2×sun / weather cover
Optional:
•2×Power Box for transmitter and
receiver, includes:
oAC/DC converter
oNET AC and power/signal
cables
•2×Switching Power Box for LAS
transmitter and receiver, includes:
oAC/DC converter with dual
output
oNET AC and power/signal
cables
oBattery (~85 Ah)
•Tripods
RET = Radio Evapo-Transpiration System
Flux station for measuring fluxes at kilometre scale
LAS or XLAS scintillometer:
•Telescopes
•2×5 m cable
•2×sun / weather cover
•Stainless steel housing (protection class
IP65) containing:
oCOMBILOG data logger
oOvervoltage protection
o2.4 GHz RF modem, directional
antenna, mounting kit and cable
(~5 m)
Optional:
•2×Power Box for transmitter and
receiver, includes:
oAC/DC converter
oNET AC and power/signal
cables
•2×Switching Power Box for LAS
transmitter and receiver, includes:
oAC/DC converter with dual
output
oNET AC and power/signal
cables
oBattery (~85 Ah)
•Tripods
Kipp & Zonen reserves the right to make changes to the specifications without prior notice.
5Depending on LAS-BET / LAS-RET configuration

14
Weather station and/or sensors4
LAS-BET LAS-RET
BET = Basic Evapo-Transpiration system
Flux station for measuring fluxes at field scale
Meteorological sensors:
•Temperature sensor*(upper level)
•Temperature sensor*(lower level)
•Wind speed sensor
•Net radiation sensor (NR-Lite)
•Soil heat flux plates (2×)
•Stainless steel housing (Protection class
IP65) containing:
oCOMBILOG data logger (plus 2
Mb PCMCIA Flash memory
cards)
oOvervoltage protection
oBarotransmitter
Optional:
•Aluminium mast (4 m) with cable guys,
grounding and sensor arms (similar to
LAS-RET)
RET = Radio Evapo-Transpiration System
Flux station for measuring fluxes at kilometre
scale
Meteorological station:
•Aluminium mast (4 m, with steel guys,
base plate and earth pins)
•Lightning rod and grounding rod
•U-shaped cross arm for:
oWind direction sensor
oWind speed sensor
•Two-sided cross arm (upper level) for:
oTemperature sensor*
oNet radiation sensor
•One-sided cross arm (lower level) for:
oTemperature sensor*
•Soil heat flux plates (2×)
•Stainless steel housing (protection
class IP65) containing:
oCOMBILOG data logger (plus
2 Mb PCMCIA Flash memory
cards)
oOvervoltage protection
oBarotranmsmitter
oSolar controller
oBattery (~12V/85Ah)
oSolar panel (~100 Watt)
o2.4 GHz RF modem,
directional antenna, mounting
kit and cable (~5 m)
*The air temperature sensors are individually calibrated (between –20oC to +50oC) and have an accuracy of 0.01oC @ 0oC in
order to determine the stability of the atmosphere.
Kipp & Zonen reserves the right to make changes to the specifications without prior notice.
Additional components
•Data logger support software (supplied on 1 CD)
•PCMCIA flash card reader (built-in version, installation software/drivers, supplied on 2
CD’s)
•Radio modem software xstreamCTU (plus additional parts: ½-wave dipole antenna, loopback
adapter, null modem adapter (male-to-male), male & female RS-485/422 adapter, AC power
adapter, 9 volt battery adapter)
•EVATION software (supplied on 1 CD)
•Additional algorithms for EVATION6
•Instruction manuals of supplied sensors and components
•1 CD containing original COMBILOG programs with calibration coefficients, pdf file of
LAS-system manual, xstreamCTU software)
6Depending on LAS-BET / LAS-RET configuration

15
3.2 STEP BY STEP INSTALLATION PROCEDURE
3.2.1 Site selection
For the installation of the LAS-system it is important that the following aspects are taken into account
in order to have a reliable operational system:
The scintillometer (see also LAS instruction manual):
•Orientation optical path: 1) it is advised to install the scintillometer such that the
orientation of the path is north-south to prevent direct sunlight into the
transmitter/receiver unit; 2) Install the LAS in a way that the path is (near) horizontal
along the surface and that it is measuring within the constant flux layer and within the
saturation free region; 3) The optical path must be free from obstacles, such as trees or
high buildings.
•Minimum height: depending on the surface conditions and the planned path length. First, the
effective height of the scintillometer should be high enough to avoid saturation of the signal.
For example high buildings, robust towers or surface topography can be used to mount the
scintillometer (see e.g. Figure 3). Second, for reliable flux derivations the LAS / XLAS must
measure within the so-called Constant Flux Layer of the Surface Layer (above the Roughness
Sublayer), where MOST is applicable. For further instructions the reader is referred to section
3.3 of the LAS instruction manual!
•Availability of net AC power (in case no solar-battery power is used).
The weather station:
•A spot that is representative for the area of interest, away from forest edges or other rough
surface elements.
•A spot, which is preferably near the centre of the path of the scintillometer (as the LAS / XLAS
is most sensitive in the centre of its path).
•Availability of net AC power (in case no solar-battery power is used).
•In case a RF telemetry link is used (based on RF modems and antennas) the installation
requirements of RF communication devices must be considered also. For detailed information
the reader is referred to APPENDIX 3 – MOUNTING ANTENNAS.
The site selection of the LAS /XLAS and weather station involves an iterative procedure:
1. Select a proper site for the LAS / XLAS (Transmitter and Receiver), such that the
observations of the instrument are representative for the area of interest, thereby taking into
account the installation requirements of the LAS / XLAS.
2. Select a representative site for the weather station, also taking into account the installation
requirements of the station (see above and section 3.2.4.1 Site selection).
3. Check the RF telemetry link (see APPENDIX 1 – TESTING RF TELEMETRY LINK)
a. Communication established →continue with step 4
b. Communication fails →go back to step 1 and/or 2
c. If one uses no RF telemetry link →skip step 3 and continue with step 4
4. Check scintillometer path for saturation and MOST applicability (see section 3.3 of LAS
instruction manual)
a. No saturation and in compliance with MOST →continue with step 4
b. Saturation is highly possible →go back to step 1
5. Install the weather station and the LAS / XLAS (and RF telemetry link)
→go to next paragraph for further instructions

16
Transmitter
Field station
Optical path
RF path
Receiver
H
LvE
Figure 3: Schematic picture of a scintillometer installed over a valley. The weather station is located in the
valley.
3.2.2 Installing LAS / XLAS
For reliable Cn
2and flux (Hand LvE) measurements it is important to meet the installation
requirements of the LAS / XLAS. These are:
oThe LAS/XLAS must be placed on a robust and vibration free contruction.
oAvoid saturation of the signal by installing the LAS / XLAS at a minimum level (depends on
surface conditions and path length).
oBe certain that the LAS / XLAS is measuring in the Constant Flux Layer for reliable flux
derivations of the Cn
2signal using MOST (depends on surface characteristics).
For detailed information the reader is referred to section 3.3.1, 3.3.2 and 3.4 of the LAS instruction
manual.
3.2.3 Power supply LAS / XLAS
Depending on the customer’s request the power supply of the LAS / XLAS can be as follows:
1. (Optional) Power Box (12VDC/3.5A, manufactured by Kipp & Zonen).
2. (Optional) Switching Power Box (12VDC/10.5A & 12VDC/0.5A, with built-in backup battery
(85Ah), manufactured by Kipp & Zonen,).
3. Alternative power supply (AC/DC converter, solar-battery power) with output specifications
that meet the requirements of the LAS / XLAS and additional components.

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LAS - ReceiverLAS - Transmitter
Steel enclosure
UCn2 and
Udemod signals
Signals
12 VDC / ~0.5 A
12 VDC / ~3 A
(+ window heater)
12 VDC / ~0.3 A
12 VDC / ~4 Amax
(+ heaters)
12 VDC / ~0.2 A
12 VDC / ~3 A
(+ window heater)
12 VDC
Figure 4: Required power supplies for LAS-BET system: 1 for the LAS-Transmitter and 1 for the LAS-
Receiver + data logger and sensors.
LAS - Receiver
LAS - Transmitter
Steel enclosure weather station UCn2 and
Udemod signals
Signals
12 VDC
2.4 GHz
RF link
12 VDC / ~0.5 A
12 VDC / ~3 A
(+ window heater)
Solar panel
(~100 W)
12 VDC / ~0.4 A
12 VDC / ~3.2 A
(+ window heater)
12 VDC / ~0.2 A
12 VDC / ~3 A
(+ window heater)
Steel enclosure
Figure 5: Required power supplies for LAS-RET system: 1 for the LAS-Transmitter and 1 for the LAS-
Receiver + data logger and RF modem. The weather station operates on solar-battery power.

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3.2.4 Installing weather station
3.2.4.1 Site selection
Selecting an appropriate site for the weather station is critical in order to obtain accurate data. In
general the site should be representative for the area of interest and away from the influence of
obstructions such as buildings, trees and other objects that might disturb the measurements (e.g.
sprinklers). Use as rule of thumb:
h10distanceminimum =(5)
where his height of the obstacle(s).
Checklist: - Terrain must be free from obstacles that might influence the wind speed,
temperature and radiation measurements.
- Terrain must be flat. As the anchoring of the mast is based on 3 provided earth nails
the soil must be strong enough to keep the loads (also during rainy periods). If
one expects that this is not the case replace the anchoring by a concrete
foundation.
- A clear line-of-sight path between the antenna in the tower and the antenna at the
LAS-receiver site in order to have a reliable RF telecommunication link.
- The site must NOT be located near commercial transmitters as their powerful signal
can overwhelm the RF radio modem leading to communication problems.
It is strongly advised first to check whether the selected site meets all above-mentioned requirements
before installing the weather station.

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3.2.4.2 Installation of mast and mounting of sensors
The mast is pre-assembled, still horizontally on the ground in accordance with dimension sketch
shown in Figure 11. Hereby care has to be taken that the admissible clamping zone is not exceeded
(indicated by an upper and lower mark with red stripes in between for each section). The mast’s
nominal length is gained when clamping the sections at their lower marks. The base plate with its
centre pin is screwed to the lowest section’s bottom.
Figure 6: Clamping zone of mast sections are indicated by red stripes printed on the mast sections.
Sensor arms (a one-sided, a two-sided and an U-cross arm), sensors (temperature, relative humidity,
net radiation, wind speed and wind direction), lightning rod, antenna are equally pre-assembled
according to the individual system configuration (see Table 3 and Figure 7 to Figure 11). Connect the
antenna cable to the antenna and use self-amalgamating tape to prevent water entering the
connector. Use cable ties to fix all sensor cables to the mast/arms and lead them to the lower end of
the mast, where at a later stage the steel enclosure will be mounted.
Figure 7: Mast, sensors, cables and guys are pre-assembled before the mast is erected.