Atmel ATAVRBFLY 데이터 시트
-22
AVR Butterfly User Guide
4271C–AVR–04/05
Figure 3-12. Temperature Sensor
An NTC (Negative Temperature Coefficient)-thermistor is used to measure the tempera-
ture. An NTC-thermistor is characterised by the fact that when the temperature goes
down the resistance goes up. Using a voltage divider and reading the voltage over the
thermistor through the ADC-channels on the ATmega169, the temperature in can be
calculated. Equation for calculating the temperature in Celsius is shown in Figure 3-13.
ture. An NTC-thermistor is characterised by the fact that when the temperature goes
down the resistance goes up. Using a voltage divider and reading the voltage over the
thermistor through the ADC-channels on the ATmega169, the temperature in can be
calculated. Equation for calculating the temperature in Celsius is shown in Figure 3-13.
Figure 3-13. Temperature Equation
β
= 4250
ADC = Value in the ATmega169 ADC Data Register – ADCL and ADCH
T
zero
= 273
°K
T
amb
=
298
°K (273° + 25°)
The temperature in Fahrenheit can be found from Figure 3-14
Figure 3-14. Fahrenheit VS Celsius
The AVR Butterfly is capable of measuring the temperature from –10ºC/+14ºF to
+60ºC/140ºC with an accuracy of ±1ºC.
+60ºC/140ºC with an accuracy of ±1ºC.
Temperature
β
ADC
1024
ADC
–
(
)
------------------------------------
⎝
⎠
⎛
⎞
β
Tamb
--------------
+
ln
⎝
⎠
⎛
⎞
---------------------------------------------------------------------------
Tzero
–
=
F
32
–
(
)
1.8
---------------------
⎝
⎠
⎛
⎞
C
=