Hey Everyone,
The goal for my project is to reliability test some electrical components with a bias of 5V, until their resistance drops to 1 MOhm. At first the components will essentially be open, and over the course of a few days the resistance will drop to ~1MOhm. I will shut-off the voltage to each part once the resistance reaches 1Mohm. The goal is to measure and record the resistance, ideally from at least 10 Mohm down to 1Mohm.
My plan was to use the 5V pin and setup a voltage divider circuit using a 500K resistor as the known. However, I get reading of 0V across the part (I assume there is no current to charge the capacitor to measure voltage).
Are there any (hopefully simple) ways that would allow me to measure this high resistance? Any help would be greatly appreciated!
Thanks,
Dan
Hi,
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Thanks.. Tom.. 
Thank you for the welcome Tom.
I have attached an image of the circuit. It's pretty simple, and would work fine if the resistances were lower.
Dan
Hi,
OPs image.
If you connect A0 to 5V what reading do your get from your code?
The problem you have is with the overall impedance of the divider.
1.5MOhms means you have a current of 5/1500000= 3.3uA.
As well as the impedance of the analog input to consider this will influence your readings
Do you have a DMM?
Make a potential divider of two 1M resistors in series across the 5V supply.
Then measure the voltage at the mid-point.
You would think it should be 2.5V, but due to the DMM having resistance as well you will find the voltage will measure lower than 2.5V.
Google arduino measuring high resistance
Tom...
