In order to exploit the full potential of our lysimeters for comprehensive and precise data acquisition, we have also developed the requisite measurement and control technology. The foundation for the water balance analysis is provided by weighing the lysimeter. This is done using the precision weighing system from UGT with weighing monitor. Even the smallest water increases such as dew or frost on vegetation can be recorded using this system. The quantity of the water flowing off on the lysimeter bottom, and the quantity of the water samples obtained using the suction cups is determined using the tipping counters attuned to the throughput to be expected. Water samples can be taken from any depth in a time- and tensioncontrolled manner using our suction probe systems. UGT has a broad repertoire of high performance sensory technology comprehensively presented in the chapters “Tensiometers”, “Soil moisture meters” and “Temperature sensors” of this catalogue for the measurement of soil moisture, soil moisture tension and temperature at any depth. The UGT data logger (see chapter “Data acquisition and power supply” are designed such that this high bandwidth of sensors can be simply connected and managed even in large unit numbers. Furthermore, after cutting the soil monolith, the objective of natural conditions which are as undisturbed as possible is met. The peripheral conditions of the monoliths cut from the soil must be controlled in accordance with the surroundings or alternatively with the aspired to scenarios. This will usually relate to the temperature and the tension on the bottom side of the lysimeter primarily so that the surface is subjected to the same climatic conditions as the surrounding area. One exception here is the control in accordance with selective scenarios for example in drought stress tests, or comparative measurements. UGT offers a heat exchanger for the temperature control on the lysimeter bottom which transfers the temperature of the surrounding soil directly to the lysimeter bottom. Since this heat exchanger must run on a permanent basis a connection to the local electricity network should be possible. With a heating or cooling system the temperature can be controlled also independently of the surrounding soil temperature such as for climate experiments. The soil moisture tension of the surrounding soil is recorded with tensiometers and then transferred to the lower edge of the soil monolith by means of a pump system via ceramic cups. Here, too, the possibility exists to conduct the control process in accordance with the scenario irrespective of the ambient conditions. PE-HD lysimeter stations can also stand in ground water due to the fact that they are water tight. For this special case the surrounding water level can be transferred directly into the lysimeter vessel via a pressure compensation system with filter. If the ground water in a lysimeter distant from the ground water is to be simulated, this can also be artificially dammed – on request also in accordance with the values of the distant ground water level which can be transferred to the control unit in the lysimeter via a radio modem. We also offer special solutions for the control of the water input on the top edge.
Lysimeters are weighed at UGT with three precision weighing cells of the accuracy class C3 / C6 and the digital weighing monitor UGT WM 100 with a large graphics- capable LCD display. The stainless steel structure made of tubular steel on B15 concrete base provide a safe base for the weighing technology. This so-called load triangle guarantees a stable and exact installation of the weighing cells as the foundation for a precise measurement. The weighing cells are installed with the assistance of shock mounts which are torque and shear-force free. The use of shock mounts facilitates mechanical flexibility of the force input into the scales. Tensions between the weighing cells through temperature fluctuations, flection and vibrations which would lead to considerable measurement errors are therefore prevented. In addition to the centralized data acquisition the new weighing monitor facilitates direct communication with the connected lysimeter. The uncontrolled water input as a result of rain can be prevented by a mobile roof which automatically moves over the lysimeters when it rains. Since the roof only covers the lysimeters when it rains, the influence of the roofing on the vegetation is very low. Rain systems can be installed for selective fully automatic watering. In the special case of a sloped lysimeter, it is also possible to record the surface run off. This is captured in a collar, recorded in a tipping counter and filled into collecting flasks as required for later investigation or as an adequate sample. In the lysimeter mode, measurement curves from earlier measurement periods can be graphically displayed in addition to settings and measurement interval changes. Irregularities can therefore be recognised directly during inspections of the lysimeter.