Overview
The LAS MkII Large Aperture Scintillometer provides continuous measurements over path lengths from 100 m up to 4.5 km. It is the only scintillometer currently available with a built-in display and control-pad. It has internal digital processing to make calculations in-situ and to store data and results. Measurements are on a comparable scale to the pixel size of satellite instruments, making LAS MkII ideal for ground-truthing applications.
The LAS MkII Evapo-Transpiration (ET) System delivers surface heat fluxes and evapo- transpiration data from a complete, easy to use, package that is individually configured to suit the specific customer requirements.
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Detailed Description
The LAS MkII optically measures intensity fluctuations (known as scintillations) using a transmitter and receiver horizontally separated by several kilometers. The scintillations seen by the instrument can be expressed as the structure parameter of the refractive index of air. The light source of the LAS MkII transmitter operates at a near-infrared wavelength of 880 nm. At this wavelength the observed scintillations are primarily caused by turbulent temperature fluctuations. Therefore the measurements obtained with the LAS MkII can be related the sensible heat flux. Compared to traditional point measurements the LAS MkII operates at spatial scales comparable to the grid box size of numerical models and pixels of satellite images used in meteorology, hydrology and water-management studies. The LAS MkII has important applications in energy balance and also water balance studies, because the surface flux of sensible heat is linked to evaporation.
Specifications
- Path length:
- 100m to 1.0 km (10cm Aperture)
- 250 m to 4.5 km (15 cm Aperture)
- Wavelength: 850 nm
- Scintillation bandwidth: 10-17 to 10-11
- Carrier frequency: 7 kHz (50% duty cycle)
Features
- Interface options: Digital RS 232/422, Analog output 0 to 2.4V
Time synchronization: via supplied GPS antenna
External sensor connection: GPS + optional sensor kit: wind speed, temperature, and pressure
Software included: Evation® (instrument control and data analysis) - Instrument control and data display: Built-in display and key-pad or remote via digital interface
- Heating system:
- Programmable lens heater (receiver)
- Self-regulating lens heater (transmitter)
- Data processing:
- Internal processing of Cn², sensible heat flux and other parameters
- Built-in data logger
Operating requirements
- Power requirements: 12 VDC / 6 W (heater off) / 54 W (maximum when heater on)
- Operating temperature: -20 to +50 °C
- Humidity range: 0 to 100% non-condensing
- Environmental protection: IP65
- Weight per transmitter/receiver: 8.5 kg
Related Documents
Downloads
Evation V2R5 Software v.V2R5 (290 Mb) 06-01-2016
The EVATION® software suite is included as standard to view real-time data numerically and graphically and provides advanced data post-processing.
Logging the Serial Output of the LAS MkII Scintillometer on a CR3000 (11 KB) 06-01-2016
This CRBasic program is meant for logging the analogue output of the LAS MkII scintillometer, in this case with a CR3000 Campbell Scientific logger.
See appendix H of the LAS MkII Scintillometer manual v1511 for additional information on logging the analog output with an external logger.
Logging the Serial Output of the LAS MkII Scintillometer on a CR6 (11 KB) 06-01-2016
This CRBasic program is meant for logging the serial output of the LAS MkII scintillometer, for use on the Campbell Scientific CR6 logger. (Note: Using the serial output of the LAS MkII is more accurate than the analogue output, gives more information, and you do not need to calibrate the input of the logger.)
It should be able to be used on other loggers, but the logger must have a RS-232 input available, and the serial commands may need to be configured to the correct channel. The program includes commands to read analogue channels for sensors from an ET system/meteorological mast, but these would need to be customised depending on which sensors are connected and what type.
The program assumes the LAS MkII is set up to send a status=2 message every second, so the send interval on the back of the LAS MkII (configuration) should be set to 1 second. Also the serial output from the LAS Digital port, should be connected to C1 and C2 of the CR6 datalogger.
See appendix G of the LAS MkII Scintillometer manual v1511 for additional information on logging the serial output with an external logger.