Abstract This paper presents the features of a pH measuring probes, the novelty of this probe is the use of an Ion Sensitive Field Effect Transistor (ISFET). This allows the pH measurements in liquids and solids probe, so it is possible to develop devices for the measurement of pH in the soil. The ISFET probe is a recent development, for this reason these manufacturers do not offer the same technical information, it is necessary to perform a characterization process to understand its operation and in order to design the steps necessary signal conditioning. The characteristics of process of the sensor are made by means of measurements of substances in which allow the control of pH and temperature. The procedure results are compared with the system HANNA model HI 991001 that it is laboratory equipment, in the case of ISFET probe use the measurement instrument IQ150. In the measurements shows that the ISFET has the capacity to obtain measurement in less time and stables that measurement instrument HANNA does.