I started connecting my PH and EC sensor boards to the Ardunio Mega. I am measuring at the input to this board around 4.5 Volts. The sensors indicate the closer one is to a true 5Volts the more accurate the sensor measurement. Currently my Arduino is powered directly from the USB port which comes from the RPi. I believe this to be a mistake. Instead a separate wiring from the main 12V supply could be connected to the DC barrel jack of the mega.
Is anyone else seeing around 4.5V on their megaboard across the VCC and GND pins at the sensors?