Hidden Response Accuracy in the ATmega328P

atmega-lm35

Hidden Response Accuracy in the ATmega328P

Some people may have known already about the temperature sensor built into the ATMEGA8, 168, 328 series microcontrollers, but the most serious enthusiast would write off the 1°C resolution as just a coarse sensor of no practical use.   I would have to say I was part of that group, until I compared the response between the two sensors.

The TI LM35DZ is a simple temperature sensor that has an accuracy of +/-0.5°C at 25°C and with 0.08°C of self heating, this should be sufficient to demonstrate the rough nature of the ATMEGA328′s internal temperature when compared to dedicated external sensor.  The TO-92′s have the best Thermal Reponses on the datasheets and are the cheapest.   Connection is straight-forward, +5VDC, Vout and Gnd with Vout to the ATMEGA328′s PC0 (Arduino pin A0).

For the ATMEGA328 internal sensor, adjustment of the voltage offset can be used to calibrate to another sensor.


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