Desenvolvimento de um dispositivo eletr?nico para calibra??o de sensores de umidade do solo

摘要

Several types of transducers have been tested to measure soil moisture content for irrigation purpose. Their use aims at optimizing water consumption and net profit from irrigation. A research was conducted at the Agricultural Engineering Department at the University Federal of Ceará and aimed at building a device to calibrate soil moisture sensors, in addition to find its major properties, such as accuracy, maximum and minimum loads. The device is composed of a 3-meter high iron tower, a scale, load cell and a data acquisition system. In one the arms of the scale a horizontal soil column was mounted and adapted to receive soil moisture sensors. In the other arm a load cell was installed in order to measure the change in water content of the soil. A electronic circuit was constructed to allow for the interfacing of the load cell with a data acquisition system. The response of the scale in volts to a load (in grams) shows to be linear between 1 kg and 50 kg, with a correlation coefficient of 0.99995 and slope of 0.09198 mV g-1. The combination to the data acquisition system used resulted in a sensitivity of 12.28 mL of water per count, and minimum and maximum loads of 1 kg and 50 kg, respectively.