Kipp&Zonen LAS MkII Scintillometer - Manual (Page 9)

.
Throughout this manual the following symbols are used to indicate to the user important information.
General warning about conditions, other than those caused by high voltage electricity, which may result in physical
injury and/or damage to the equipment or cause the equipment to not operate correctly.
Note Useful information for the user
1.1 Product overview
The LAS MkII Large Aperture Scintillometer is an optical instrument with a 150 mm diameter beam that is designed for measuring
the path-averaged structure parameter of the refractive index of air (C
n
2 ) over horizontal path lengths from 250 m to 4.5 km 1 . When
the supplied 100 mm diameter aperture restrictors are fitted, the path length can be from 100 m to 1 km 1 .
LAS MkII uses a transmitter and receiver horizontally separated by several kilometres to measure intensity fluctuations in the
air known as scintillations. This is the same effect, but of much smaller amplitude, as the ‘shimmering’ of air over very hot or
cold surfaces that causes a mirage.
The scintillations seen by the instrument can be expressed as the structure parameter of the refractive index of air (C
n
2 ). The
light source of the LAS MkII transmitter operates at a near-infrared wavelength of 850 nm. At this wavelength the observed
scintillations are primarily caused by turbulent temperature fluctuations.
Therefore, C
n
2 measurements obtained with the LAS MkII can be combined with temporally and spatially coherent meteorological
observations of air temperature, wind speed and air pressure to derive the free convection sensible heat flux (H
free
). An accessory
meteorological sensor kit is available for this purpose, which connects to the LAS MKII receiver.
The LAS MkII is self-contained. The system can be locally configured at the receiver with a display and menu keys and has
internal digital signal and data processing and data storage. When the data is exported to the included EVATION software
package running on a computer the surface sensible heat flux (H) can be calculated.
Compared to traditional point measurement systems, the LAS MkII operates at spatial scales comparable to the grid box size of
numerical models and the pixel size of satellite images used in meteorology, hydrology and water management studies. The LAS MkII
has important applications in energy balance and water balance studies, because the surface flux of sensible heat is linked to latent
heat flux (L
v
E ) and evapotranspiration (ET). For these measurements a complete LAS MkII ET System is available.
This manual provides information related to the installation, maintenance, calibration, product specifications and applications
of the scintillometer.
If any questions should remain, please contact your local Kipp & Zonen representative or e-mail the Kipp & Zonen customer and
product support department at:
[email protected]
Please go to www.kippzonen.com for information about other Kipp & Zonen products, or to check for any updates to this manual
or software.
1 The maximum usable path length depends upon the atmospheric conditions, the path lengths given are for ‘clear’ conditions (visibility 10-20 km). In general, it is
best to use the scintillometer at full aperture at path lengths down to 250 m, and the aperture restrictors for shorter paths. However, for field-scale measurements
at a range of distances up to 1 km it may be convenient to leave the restrictors fitted.
1. Introduction
9
Instruction Manual - LAS MkII Scintillometer
1.2 Key parts of the LAS MkII Scintillometer
1.2.1 Transmitter and receiver
The drawing shows the key common parts of the LAS MkII transmitter and receiver:
Sun shield fitted to the mounting for the alignment telescope
Tilt (vertical) adjustment screws
Pan (horizontal) adjustment screws
Transmitter window, with heater and Fresnel lens behind
Drying cartridges
Baseplate
1.2.2 Transmitter rear panel
The drawing shows the key parts of the LAS MkII transmitter rear panel:
Power indicator (red)
Transmitter power adjustment knob (remove screw-on cover)
Signal output connector (4-pin)
Power input connector (12 VDC)
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1.2.3 Receiver rear panel
The drawing shows the key parts of the LAS MkII receiver rear panel:
Display
Power and status indicator (green)
Menu navigation keys
Meteorological sensor kit connector (8-pin)
Analogue signal connector (4-pin)
Power input connector (12 VDC)
Digital interface connector (8-pin)