Well, here's my problem. I got rid of the 10 k pot just in case it was flaky. I replaced it with two 220 ohm resistors in series across the 5V and ground of the arduino. With the A0 pin not connected to the junction the junction measures close to 2.5 volts as expected. When the A0 lead is connected the voltage across the bottom resistor drops to .4 volts!!!! To say I'm bumbfuzzled about this result would be a mild understatement. Obviously something is going on here that I'm not aware.
Resistance of both resistors measured with Fluke 77 at 221 ohms. Same fluke was used to measure the DC voltage at the junction of the resistors.
This is the simple sketch I'm running on the arduino:
#include <LiquidCrystal.h> // I have a LCD connected to display the result
LiquidCrystal lcd(12, 14, 11, 7, 8, 9, 10);
int sensorPin = A0; // select the input pin for the
int sensorValue = 0; // variable to store the value coming
sensorValue = analogRead(sensorPin);
I must be making some mistake with this sketch. I can't see it. LOL
Moderator edit: [code] [/code]