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. Thermocouples are nonlinear and when use this thermocouple it should be convert to control the temperature and the compensation. The temperature range of thermocouples is from -200 to 1750 °C. The accuracy of thermocouples is from 0.5 to 5 °C.Semiconductor temperature sensor is in the form of integrated circuits. To measure the temperature most of these sensor employs a modified forward diode voltage drop method .We have five types of semiconductor based sensors Voltage Output Temperature Sensors, Current Output Temperature Sensors, Digital Output Temperature Sensors, Resistance Output Silicon Temperature Sensors and Diode Temperature Sensors.