The unit consists of a tunnel equipped with an axial fan at one of its ends. A battery of electric resistors installed after the fan will heat the air flow entering the drying chamber. The chamber with transparent inlet door contains a set of trays suspended on the pan of a balance mounted above the dryer. This dryer has been designed to study the commonest industrial drying method of solids consisting in blowing a flow of hot air onto some trays where wet material is arranged. The total capacity of these trays is of approximately 3.5 kg of solid. Varying the air speed by an inverter and the power of resistors by a thyristor will enable to vary the temperature of inlet air. The heating elements are completely protected from overheating by a safety switch and they can be switched on only if the fan is turning. Moreover a minimum speed for the fan has been preset. A digital anemometer will measure the air flow rate. Temperature and relative humidity are measured before and after the drying chamber thanks to two transmitters of temperature/humidity.