Ways to accurately heat up SMD component(s) on a PCB to a specific temperature?h
The device is pretty accurate as-is, probably more so than your thermocouple meter at low-ish temperatures. I suspect you'll make things worse than they are from the factory with such crude equipment. 

But if you insist, glue a 1K platinum RTD element to the top of the device and put it in a convection oven with simple temperature controller (or, preferably, a proper environmental chamber). 

Use a good ohmmeter to measure the temperature of the device.