viswapraveen:
Hi,Is it necessary to use the pins 5V or 3.3V or Vin of Arduino Uno in the external circuit in order to read analog voltage output from the external circuit using Arduino Uno ?
Pls advice.
Thanks
No. You only need to connect the UNO's ground to that of the external circuit, and ensure that the input voltage from the external circuit is not higher than the UNO's Vcc, (5V).