Inside my thesis of master degree, there is the description and calculations of the electronic interface and protection of over and under voltage betwen the Arduino Due and the Operational Amplifier 741. There is too the software of the control action. It can be accessed at www.uff.br/mcct/ select the words ALUNOS (Students) and TURMA 3 (Class 3), then my name José Luiz Guarino. Unfortunately it is written in Portuguese but who knows Spanish can understand it. There is inside, at the begining of the thesis, a short description in English of the entire work. A request of patent of the interface and protection circuit and the register of the software was made at the INPI (Brazilian Institut of Industrial Property).