I am trying to measure the temperature from four MCP9700AE temperature sensors (http://www.digikey.ca/product-detail/en/microchip-technology/MCP9700A-E-TO/MCP9700A-E-TO-ND/1212508) using an ATMega 2560 microcontroller. However I get different temperature readings depending on which 5V input on the board and which ground on the board I use. I measured the potential difference between the 5V inputs and grounds using a multi-meter and they are all the same. So I don't understand why the temperatures are different. Anyone have any ideas?
By the way I tested this using two different AT Mega 2560s and the results were the same.
So I hooked up a 10 DOF sensor that has a temperature sensor as well to the ATMega. (https://www.adafruit.com/product/1604)
This chip requires an SDA and SCL connection. Now all the temperature sensors give 21 C temperature reading. Not sure what this modification does as I didn't change anything for the MCP9700A.