There's no voltage. Maybe your meter could register drop in resistance (from ~∞ to ~0). Think of it as simple push button. Or, to put it differently, you need t

There's no voltage. Maybe your meter could register drop in resistance (from ~∞ to ~0). Think of it as simple push button. Or, to put it differently, you need to supply your own voltage and it will flow for a moment when the camera triggers the flash (closes the circuit), and you can register the spike. Edit: the circuit is insulated from the camera electronics since some flash lights can send 250V or even more trough the PC socket - it acts as the pathway for the charge from capacitors to the bulb (in some, esp. older strobes).