Hi Kelvin,
!) In response to your questions, the equations descibd in the TMP006 and TMP007 for calibration are designed to account for an imperfect world. Heat sources other than IR energy from the object will cause offsets and non-linearities in teh response. These background sources can be from other objects in the scene if the object does not completely fill the field of view, from air convection or from thermal conductance of nearby components. So yes, in general So is teh clope and should need only one point but in practice is almost never sufficient.
2) yes, plotting this shuld yield a straght line vs object temperature at a constant die temperature.If the die temperature is chanigng then there may be an offset because it will change the thermal radiation exchange with the background.
So if the line does not go through (0,0) that is OK, it just means that the object is not the only source of thermal energy. However, the should be a straight line,
If you send an email to wmetz@ti.com I will send some sample data.
Regards,
Werner