Resistance Temperature Detector (RTD) is highly predictable if compared to the surrounding temperature, it give us accurate and consistent temperature measurement. We used some temperature sensitive materials in building the resistance temperature detector like platinum, nickel and copper. It give us high stability and reliability. In RTD by knowing the resistance measurement of pure electric wire we can measure the temperature. It has good linear characteristics along temperature ranges. Thermocouples consist of two wire legs and this two wire legs are made of different metals. The two wire legs are connected together at one end to create a junction, from this junction we can measure the temperature. It creates a voltage when there is a change in the temperature. We use thermocouple in industrial, scientific and OEM applications. The temperature range of thermocouples is from -200 to 1750 °C. The accuracy of thermocouples is from 0.5 to 5 °C.