This is a design circuit for temperature to digital converter circuit that is based control by LM35 IC. This LM35 is precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in ° Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±1⁄4°C at room temperature and ±3⁄4°C over a full −55 to +150°C temperature range. This is the figure of the circuit schematic;
How this circuit can work? This circuit is supply the power using 5VDC that produce by power supply. And then the voltages enter the circuit as analog signal. This signal is enter to the LM35 to detected and calculate by the sensor. The output signal from LM35 send to the ADC converter to processing the digital signal. Before the digital signal is send to the controller by pin 8, there are voltage for reference that given to the amplifier. This reference is using as compare when calculating in microcontroller or microprocessor.