I work in a factory where an instrument's bus contact we have has two connectors, one for 24VDC (used to power the instrument), and the other is for 110VAC (used for a bulb). Now, for some reason, the two connectors got melted and 110VAC got mixed with 24VDC. Our 24VDC is ungrounded, but for some reason when we measured the Common of the power supply it was reading 24VDC. Fortunately, when the cable that is carrying the digital signal from the instrument was touched (by mistake) by one of my colleagues, he received a slight shock, which I think was the 24VDC. But when measured by a multimeter, it reads 110VAC. Now, I'm confused, what happens exactly when we mix an ungrounded DC supply with an AC supply?