i am building a own circuitboard LM35s and a Voltage devider from 40 to 5V ,10mm below an arduino Uno, and i was wondering where the most EMI (electro magnetic Interference) occur on the Arduino board. so that i can place strategically the Temperature sensors and Voltage devider
I'm not sure, but since nobody else has answered I'll take a guess and say the end with the usb connector. There's a crystal and switching power supply on that end. The safest bet would probably be up in the corner between the ICSP header and pin0.
For general pcb layout, you try to keep the analog circuitry segregated from the
digital cktry, and especially away from the crystal, which will have the highest
frequency noise on the board. If you're laying out your own board, just put the
analog parts in the same general area as the analog header is on the regular UNO
board, and keep all the other stuff on the other side of the cpu chip.