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17 July 2006

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Windmill Aids Climate Change Research

Atmospheric carbon dioxide concentration and temperature are increasing. Periods of low water availability are expected to increase in Mediterranean and other ecosystems. Researchers in Spain at the Institute for Natural Resources and Agricultural Biology of Salamnca (CSIC) and the University of Navarre, have simulated predicted increases in CO2 and temperature and investigated the effects on crops. To monitor and control environmental conditions they used Windmill software and a Microlink 751 data acquisition unit which they connected to their PC's USB port.

Much of previous research on elevated CO2 has been done in fully-controlled environments using constant temperature and electric lighting. Plant behaviour in the field frequently differs from that in such facilities. The Spanish researchers used temperature gradient tunnels to more realistically simulate aspects of the effects of future enviromental change. Their near-field technique had the added benefit of being enormously cheaper than other similar experiments.

Measuring CO2 Concentration, Temperature, Humidity and PAR

Compact Microlink 751 USB measurement unit

The temperature gradient tunnels contained measuring and control equipment. Carbon dioxide concentration, for example, was continuously monitored by an infrared gas analyser. Ventilated temperature and humidity sensors and air probes connected to another infrared gas analyser were placed 60 cm above the plants. Quantum sensors were placed on top and inside each tunnel to record photosynthetically active radiation (PAR). The data was continuously recorded by a computer using the Microlink 751 DAQ unit (pictured right) and the Windmill software.

Automatically Opening and Closing CO2 Cylinders using Windmill Software

As well as the standard Windmill software suite, which includes logging and charting modules, the researchers used the Windmill Test-Seq programming tool. With this they controlled solenoid valves which kept open or closed one of two sets of CO2 cylinders supplying the gas to the elevated CO2 tunnel. When CO2 concentration decreased below a fixed level, signalling that one of the cylinder sets was exhausted, the corresponding valve was closed and that of the other set opened.

Test-Seq was also used to sequentially measure CO2 concentration at several places in the tunnels with the same infrared gas analyser. The programme successively opened for a fixed time interval one of the six solenoid valves sampling the air in the tunnels.

Windmill Test-Seq is easy to use with no prior programming experience needed. It simply interprets a text file of commands that are designed for data acquisition tasks.

Converting Analogue Measurements to Digital Values

The Microlink 751 captured the analogue measurements and converted them to digital values that could be stored by the computer. Each 751 unit can capture data from 16 sensors and probes of various types. It can also switch digital outputs and hence could be used to control the solenoid valves according to the commands sent by the Windmill software.

Further Reading

Aranjuelo, I., Irigoyen, J.J., Perez, P., Martinez-Carrasco, R. and Sanchez-Diaz, M. 2005. The use of temperature gradient tunnels for studying the combined effect of CO2, temperature and water availability in N2 fixing alfalfa plants. Annals of Applied Biology 146: 51-60.

Perez, P., Morcuende, R., Martin del Molino, I. & Martinez-Carrasco, R. (2005) Diurnal changes of Rubisco in response to elevated CO2, temperature and nitrogen in wheat grown under temperature gradient tunnels. Environmental and experimental botany, 53, 13-27.

Microlink 751 Unit

Windmill Software

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