This project follows three previous others, always seeking to improve the prototype. The first project was developed by Jean Philippe Dines Labarrere, finalized in December/2013, who developed a preliminary prototype of a magnetic tachometer for drilling columns, being necessary some simplifications as the use of a Nylon pipe with magnets attached to simulate the drilling column. In a second version of the magnetic tachometer, in the final project of Luis Philipe Batista e Silva, finalized in July/2014, there were changes in the previous prototype, initially replacing the Nylon pipe by a steel tube extracted from an actual drilling column, and then making improvements in the data capture algorithm and processing. The third version was performed by Diogo Spazzafumo Reinoso, where the existing prototype has improved, aiming at approaching the model to reality. Initially, it was replaced the fluxgate magnetometer, used by both previous projects, by a GMR sensor (giant magnetoresistance). Later, a DC motor was coupled to the carbon steel tube, allowing a better speed control. Finally it was integrated in a closed-loop system, allowing the user to set the desired speed in an interface developed in LabView environment, and controlling the motor supply voltage so that it reaches this speed. In the current version improvements were made in the control of DC motor, the form of data acquisition has changed and the power circuit was improved, leading to greater protection for the same and a faster measurement of the rotation speed.