I've got a 12V source which I want to measure the voltage (or basically, just to check it's there) so have a voltage divider. Currently, with a 10k and 3k resistor, that brings it down to 2.77V and well within the Analog Input of an Arduino to measure, which is great. With this setup, it pulls ~923uA of current, but with a 10M and 3M resistor I get around ~923nA. Obviously I want to pull as little current as possible, but would the current with the 10M and 3M resistor be too low for the arduino to pick up? I read somewhere someone saying that the max should be 10k and 3k resistors for Arduino to read it reliably, but can't find it anywhere now and it's just sticking in my head.
This is probably a silly question, but I don't have an arduino to test it with right now.