The Non-Contact Temperature Measuring Instrument is based on the principle that each body above absolute zero temperature emits energy as electromagnetic radiation. The intensity of these radiations is proportional to the temperature of the body. There are three types of IR transmitters and the selection of the particular type depends on the application. The "wideband thermometers" (total radiation) are used for low temperature application. The "narrowband thermometers" (monochromatic) are used for high temperature measurement and/or measurement on special materials. The "ratio thermometers" are used whenever the target is partially visible or for the objects with very low emissivity or when there is smoke, dust, steam which obscures the vision pathway. Apart from the selection of the type of thermometer the emissivity is one of the important factor that plays the role in IR temperature measurement. The IR energy emitted by a surface differs according to the composition and physical conditions. The parameter used to characterize object surface is called emissivity. The one more very important factor which decides the selection of the model is on the basis that whether the measurement has to be done continuously (process) or for the temporarily (portable). In short the selection of IR temperature transmitter is very complex process and needs the complete study of the application.