M. Hiles, Canada
We had a problem with a controller that was locking up and nobody could figure out why. We checked the installation, parameters, everything. I was at my peak of frustration, staring at my Fluke 89 multimeter, thinking what could it be? Then, I saw my seldom-used function; Hertz (frequency). I checked and sure enough it (Hz) was all over the place. As it turned out, a motor frequency drive was causing interference on the power supply. Some days you just have to step back, think outside the norm and have the right meter!