The technician failed to consider the peak voltage of the AC line!



Challenge question: one thing the technician did right in this circuit was use a transformer as the front-end of his signal conditioning network. Explain why this was a smart idea. In other words, why would it possibly be worse to simply use a resistive voltage divider to do all the attenuation, instead of using a step-down transformer to do part of it and a resistive divider to do the rest?