SMUT - Sistema de baixo custo para aquisição de temperatura e umidade relativa do ar para manejo de irrigação

Abstract

The air temperature (T) and relative humidity (UR) play a fundamental role in agricultural management, being used, for example, in the reference evapotranspiration estimative. Their values are usually obtained in meteorological stations, which costs vary from US$ 1,000.00 to US$ 10,000.00. This price makes them of hard access to most users. Thus, the objective of this work was to develop a data acquisition and storage system of T and UR (SMUT) for low cost agricultural purposes (estimated at US$ 70.00). The System was built using a DHT22 sensor (AM2302) installed in a shelter, a real-time clock (RTC), and a SD card recorder coupled to an Arduino board. Readings were taken every ten minutes and, at each hour, averages of T and UR were calculated. For comparison the system was installed near two automatic meteorological stations in Goiânia-GO (Weather station / UFG) and data were collected from October to December 2016. To compare the data, relative error (EPE), square root of average square error (RMSE), average absolute error (EMA), Pearson’s simple correlation coefficient (r), and Willmott’s concordance index (d) were calculated. The results showed that there is a strong and positive correlation between the SMUT data and the other stations (r > 0.87), with a relative error around 6% and a high degree of accuracy (d>0,99). Therefore, it is recommended the use of SMUT for agricultural monitoring of T and UR, in the range of 17 to 35oC and 32 to 100%, respectively.