Weather Monitoring 25


Acoustical precipitation sensors “hear” the precipitation impact, like a person under an umbrella hears whether it is raining heavily or slightly. However, with regard to snow or similar smooth precipitations this system shows its weakness.


Almost new on the market are precipitation sensors based on radar technique, but like the optical systems these devices are better suited to measure intensity of precipitation than for quantity of precipitation.


LAMBRECHT offers a range of proven tipping bucket rain sensors, which are necessary for the precipitation survey in a precipitation network (in accordance with the Joss-Tognini principle). The operation mode of these resembles the other tipping buckets on the market, but a special optimised design distinguishes the LAMBRECHT tipping buckets. The low- priced but professional precipitation sensor of LAMBRECHT is model 15189. The compact and robust design characterises this sensor and is available with or without heating device. Model 15188, apart from the optimised heating, offers options with analogue output and integrated linearisation. Especially for high mountain applications the company offers model 1518H3 with three independently regulated heating circuits whereby this device is perfectly dedicated to measure also water volume of hail and snow.


The Data logger Data logger TROPOS100


The core of a precipitation station is the data logger TROPOS-100 which records, linearises and stores the precipitation quantities on an ex- changeable memory card. For the linearisation the data logger detects the precipitation intensities over a fixed period of time and amends the precipitation quantities depending on the actual intensity. The storage of the data can be carried out in permanent or event-driven manner. At the event-driven storage the logger just memorises the days with rainfall. That way, the storage volume will be minimised and data graves


filled with zeros can be avoided. Depending on the configuration the data will be called-up and collected by the control centre. There, as described below, a corresponding alarm will be generated (alarm- function-1). Alternatively the data logger actively contacts the alarm centre, after exceeding the adjusted threshold (alarm-function-2). Certainly the data can be read on site from the memory card.


The Alarm centre


All data from the rain gauge network are to be collected at the central office of the disaster management authority. The alarm control centre of the introduced example consists of a PC including evaluation software and up to 4 modems (+1 modem for direct access to the stations only).


The communication with the alarm control centre can be carried out via GSM modem for example. GSM modems represent the most cost- effective communication alternative and are absolutely sufficient as the data volume is very small.


The Software METEOWARE RAIN


The precipitation software METEOWARE RAIN allows the operation of a meteorological network up to 255 precipitation stations. The software permits a graphical and a tabular evaluation of the collected precipitations and offers the possibility to export the data to other software applications. By means of the METEOWARE RAIN, the meteorological network can be monitored from afar. For the alerting at certain precipitation incidences, the software disposes of two construction stages. Generally an alarm will be generated, when a certain precipitation quantity is trespassed within a certain period of time. An corresponding message can be generated at the beginning and at the end of a precipitation event.


Alarm function 1


In the basic construction stage, the alarm control centre calls the chosen precipitation stations and asks for the data which have been recorded on the data logger (TROPOS-100) since the last recall. In case any of the recalled data exceeds the threshold values adjusted in the METEOWARE RAIN, a visual and acoustical warning will be emitted.


Alarm function 2


In the second construction stage, a data- receive service as a windows system service is running on the PC in the alarm centre, which is in receiving mode. In this case, the threshold values have been deposed directly on the data logger, which always “calls” the PC via a free telephone line if the adjusted threshold values are exceeded. Depending on the configuration, the precipitation station transfers the alarm message respectively the stored data. The alarm message can be released visually and acoustically on the PC. In both cases, the software can administrate up to 4 modems and the control centre receives the data respectively the alarm messages via these modems.


Conclusion


Due to the global climate change it becomes more and more important to be well prepared against possible inundations. The most reliable flood warning system with the best price- performance ratio can be designed by the high quality LAMBRECHT tipping bucket rain gauges together with data logger and individual modem for data transfer. This common and well- proven system requires just a little maintenance and works most reliably. In consequence, the LAMBRECHT tipping buckets are the most recommendable precipitation sensors.


Alarm function 2


Alarm function 1


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New Ultrasonic Weatherstation? Provides Advanced Weather Monitoring For Any Application


Airmar Technology (USA) has introduced the new LB150 Ultrasonic WeatherStation. This advanced electronic device is capable of accurately measuring and recording a wide range of important meteorological factors without a single moving part.


The LB150 can be applied to any industrial application needing real-time, site-specific, weather information. Applications include wind farming, chemical processing plants, weather vehicles, and agriculture. The compact and rugged LB150 accurately measures and calculates apparent wind speed and direction, barometric pressure, air temperature, relative humidity, heat index, dew point, and wind chill temperature. With its standard internal compass and built-in GPS, Airmar’s Ultrasonic WeatherStation can even provide highly accurate true wind speed/direction computations when used in a moving vehicle.


Since Airmar’s LB150 has no moving parts, it provides superior accuracy and longevity in the field. The LB150’s wind readings are not affected by common problems like bearing wear, dirt, or birds, which can all result in failure or data inaccuracy for mechanical wind and weather measuring devices.


Airmar’s WeatherCaster PC software provides a range of weather data display screens and background options for simple operation and customisation by the user. The standard RS422 data


interface gives customers the flexibility of designing application-specific software, or the optional Airmar USB converter plugs directly to your PC.


Reader Reply Card no 65 Reader Reply Card no 66 May/June 2010 IET


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