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LM35DZ negative temperature

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medo73

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I tried to connect Vout with pull-down resistor on ADC of Pic16f877 and
two diodes serial 1n4148 on GND pin to make offset.
I tried to measure temperature for about -5°C and the result are always +2 to +3
what can i do to measure the correct temperature?
the equation is the next:
Temperature = (AD_value - 195) / 2.031
 

leemarrow

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Hi,
you need to add a resistor as indicate in datasheet.
For calculation the zero degree is equal 1,2 Volts if you add 2 diodes
So, 1,3 volts are 1 degree and 1,1 volts are -1 degree
regards
 

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