Design And Development Of Minitype Automatic Weighing Lysimeter

Using domestic strained integrated resistor as weighing sensor, AT89C52 single chip as control unit, combined with arithmetical magnification, analogtodigital conversion (A/D), real time clock, liquid crystal display (LCD), and series communication interface, a minitype automatic weighing lysimeter is developed. That made measurement of evapotranspiration become conveniently and effectively in studying on water use of crops. The developed apparatus can automatically measure evapotranspiration at setting up interval and memory the data through a 32 KiloByte Data Storage Memory. Measured data can be transmitted to personal computer by RS232 series communication interface. Apparatus will be trigged at measurement time by a real time chip set in it. And users can see measurement parameters, measuring date and time etc through LCD of apparatus.Testing and application of developed apparatus in laboratory time after time, We found that its stability, reproducibility and precision meet practical application completely. Its maximum absolute error is about ?3g and maximum relative error is only about 0.4%. Evapotranspiration of tomato Measured by our apparatus in Laboratory during a consecutive period presents very well its change in reality. For its minitype, the apparatus can specially used for comparison test in potted crop breeding or experiment of watersaving culture in laboratory.Element selecting, electric circuit design of hardware, software development of the apparatus, method of data processing and measures of anti interference are introduced respectively in the paper. Source of apparatus's errors and improve method are also analyzed and discussed. In the end of the paper, the speculation of the further improvement and perfectness of the apparatus are put forward.