To protect an analog signal we replaced plain ribbon cable with shielded ribbon cable. The shielding we connected to earth ground on ONE end. Now the humidity reading is erratic. Switching back to plain unshielded ribbon and the problem goes away. This defies all the rules in my book - What could I be overlooking?
The aim was to reduce the chance of getting zapped by "tribo-electrics" inside this dry box with fans and sundry metal mesh trays. Which are grounded to earth ground, more or less, through steel pins resting on aluminum rails... I did not want lightning to strike signal ground, nor any wire in that harness. My fear of these discharges may be overblown but I'm chasing gremlins & have no clue what to measure where! This is my introduction to ground loops then. Although I have difficulty seeing a "loop" in this scenario. To thicken the plot, how about connecting shield to ANALOG ground? I'd hate to have the ADC zapped!
Thank you for your insights.
Earth ground? Try connecting the shield to the circuit ground (common) at one end. Then try the other end.
Good luck.
John
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