I built a lovely little EMF detector using this as a starting point:
http://blog.makezine.com/archive/2009/05/making-the-arduino-emf-detector.html
The probe is connected to A5 with the resistor connected to ground on the Analog pin side of my protoshield. I've now connected a potentiometer (which will eventually control some things but does nothing for now) to A1 with its ground pin connected to the same ground rail as the A5 probe. If I connect the pot to the board but pretend it doesn't exist in my sketch, the EMF probe on A5 returns its appropriate readings:
Probe: 147
Probe: 293
Probe: 585
Probe: 293
Probe: 74
However, if I make variables for the pot:
int potPin = 1;
int potVal = 0;
and then take a reading:
potVal = analogRead(potPin);
As I turn up the pot, the probe quickly maxes out:
Pot: 0 Probe: 147
Pot: 24 Probe: 439
Pot: 52 Probe: 1023
Pot: 76 Probe: 1023
Pot: 100 Probe: 1023
and stays at maximum until I turn the pot back down to almost zero. There's obviously some sort of interference between the two. I think it's a software problem because the interference only appears when the Arduino (Uno SMD) begins to read the pot, but I'm at a loss about what to do or where to look. Any guidance anyone here can offer is immensely appreciated.