My ESD mat grounding method was backwards for months
I was using a daisy chain from the wrist strap to the mat, then to the outlet ground, for like 6 months. A customer in Tulsa brought in a board that kept frying and when I checked with my multimeter, the mat had 12 volts AC on it. Turns out I had the resistors on the wrong side of the chain, the plug was doing nothing. Have any of you caught a bad ground loop that way, or is it just me?