maximum centigrade value
You've to fit the input signal to the ADC converter dynamic, in other word, your PIC ADC can give 10 bit word from a signal between 0 and 5V then at first you need to fit the analog signal with the input range of the used ADC.
If you like to measure a temperature value between 2 °C to 150 °C look at the LM35 specification, if you're using the first schematic (Figure 1 into the datasheet) you have 10 mV every °C then 2 °C -> 20mV, for 150 °C you should be able to read 1.5 V.
Now you've a problem, for a 10 bit DAC you've a minimum of 5/1024=4.88 mV then you should be able to read 20 mV and correct understand it, but the maximum value of your interval is only 1.5 V, less than the maximum allowable of 5V then your reading will be compress because 20 mV is approx equal to a digital value 4 and 1.5 V is equal to 307.2 a total range of about 303 digital value regard a total available of 1024. You need to fit the analog signal to the 0 - 5 V range, or better from 0.5 to 4 V, to do this use operational amplifier and then make the needed calculation into the microcontroller.
As other way you can use inexpensive digital termometer LM70 with SPI interface, precision is 0.25 °C for a temperature range between -55 to +150 °C, with this device no need to use ADC or other amplifier, simply read the digital value and make your scaling calculation inside the microcontroller.
**broken link removed**
**broken link removed**
Hope it help
Bye
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