top and bottom half sensor temp
Added by Kyle McKinney over 5 years ago
I have noticed that there is a big temp difference between the top and bottom half of the sensor.
Vptat_Top: 2.12863V : 35.3651C
Vptat_Bot: 2.16838V : 44.065C
I took a look at the sensor with a thermal camera and did not see a difference in temp between the two halves.
I assume the difference is cause artificially by the devices used to measure each half being slightly different?
The difference is seen even right when the camera is turned on after having ample time off for the two halves
RE: top and bottom half sensor temp - Added by Michael Williamson over 5 years ago
This is why we use an external thermistor attached to the sensor for temperature reporting. We have observed quite a bit of variance in the VPTAT voltages from chip to chip wrt temperature.
Each half of the 2521 sensor requires a factory level calibration and lookup that BAE has not provided. We don't have an easy way to measure the voltages from VPTAT and create lookup table based on temperature at factory. The values we are dumping assume a curve that is only an approximation. I would use the thermistor sensor temperature for monitoring sensor temperature, or if you want to develop your own lookups from the measured voltages that would also work.
We did some initial measurements of the halves as well as case, and you are right, there should not be a large difference between the top and bottom halves.
RE: top and bottom half sensor temp - Added by Kyle McKinney over 5 years ago
Ok great thanks! Just wanted to double check.