Temperature sensor on 32U4

The ATMEL docs indicate that the ATMega32U4 contains a temperature sensor. Is the sensor intended to measure the operating temp of the chip itself, or is it more useful in measuring the ambient temp surrounding the chip ? The sensor is talked about briefly in section 26.4.

The docs say

During the production, a calibration is done at two temperatures (+25°C and +85°C, with a tolerance of +/-10°C(1)). At each temperature, the temperature sensor value Ti is measured and stored in EEPROM memory(2)


Be aware that if EESAVE fuse is left unprogrammed, any chip erase operation will clear the temperature sensor calibration values contained in EEPROM memory.

That does not really tell me where they are in the EEPROM, nor if they would have been erased by the time I receive a board containing a 32U4.

Trying to decide how useful the sensor might be, or not.

Replying to myself. I found a post on arduino.cc that clearly states that this is the chip temp, and not the ambient temp.

All temperature sensors measure their own temperature. A problem can arise when a temperature sensor uses electrical power, which heats it.