Read 5V PIN

Projects Programming
1

Hi,

I'm usin LM35 to get the temp with this code:

int value = analogRead(sensorPin);
float millivolts = (value / 1023.0) * 5000;
tempActual = millivolts / 10;

When I take the value in 5V with an external tester, it show 4,98-4,95, so I think I need to check the value of the 5V PIN before read the sensorPin for calculate the real temp.

Can I use this circuit to read the actual value in 5v PIN?

Thanks

2

Most (all?) Arduino ADCs have a reference voltage so the power supply voltage is not very critical.

3

I tihnk I need to know the value of 5V PIN to use it in:
float millivolts = (value / 1023.0) * 5000;
Because if the real value in 5V is 4,97 I have to use:
float millivolts = (value / 1023.0) * 4970;

It's ok?

Thanks