This research aims at the development of a methodology for experimentally characterizing a PTC polymeric resettable thermistor LP60-110, used as an overcurrent and over temperature protection device. Uncertainty of measurement of the parameters, such as temperature, voltage, current and ohmic resistance is also determined. The PTC (Positive Temperature Coefficient) polymeric resettable thermistor started to be used in the 90`s, as a very important protection device because of its special characteristics. It can be used as an over current and over temperature protection device in electronic circuits, for engine start-up and as a temperature compensation device. An electric circuit was built to measure the thermistor characteristics, consisting of an stable voltage source and a variable resistance in series with the thermistor, which was place in a dry oven. A K type thermocouple was attached to it, so that its temperature could be measured and controlled. A chronometer and two multimeters were used as measuring instruments. By gradually decreasing the circulating current through the circuit, the Joule effect could be neglected, and the thermistor resitance was made only a function of ambient temperature, which is easier to measured. The acquired data were used to build several characteristics curves, which were analyzed and compared to the available ones from the manufacturers. Due to the fact that there are not many available information about the sensor in the market, the main contribution of this work is the development of a systematic procedure to obtain the thermistor performance data, so that the manufacturer data can be verified, together with its uncertainty, providing at the same time information not presently available in the market for system designers.