Well, you'll have to open the circuit. 'Tailcap' current is easy to measure since it doesn't require disassembly. Otherwise you'll have to pop a wire between the driver and LED to measure it.
Well, you'll have to open the circuit. 'Tailcap' current is easy to measure since it doesn't require disassembly. Otherwise you'll have to pop a wire between the driver and LED to measure it.
Measuring at the tailcap may give different current than is flowing through the LED - for example a 2-cell lamp with white LED will have a boost converter to generate enough voltage for the LED Vf, the boost in voltage comes at the cost of higher battery current.