One of the typical sensors used in aircraft to monitor a wide range of temperatures is Resistance Temperature Detector (RTD). But because it will compromise the precision of the temperature data, self-heating error has grown to be a significant issue for all temperature sensors, including RTD. Increased excitation current is the main reason self-heating issue occurs. In order to reduce the self-heating inaccuracy in RTD, this paper's goal is to examine the excitation current range. To replicate the excitation current that was injected into the Pt 100 RTD (Platinum RTD Standard IEC 751 Class B) and does affect the self-heating error, an experimental technique and comparison with theory were employed in this work. The average excitation current ranges from the experiment, which was carried out at temperatures between -200 °C and 850 °C, is 0.7992 mA to 5.4066 mA, and the self-heating error is between 0.0370 °C and 2.3665 °C. Additionally, 1.85 mA offers as the optimal excitation current at all temperatures.