Abstract: An arrangement for measuring an internal clock within an electricity meter includes an optical communication circuit within the meter, an optical detector external to the meter, and a frequency counter. The optical communication circuit within the electricity meter is operably coupled to receive a pulse output of the meter's internal clock, and is further configured to generate a corresponding optical pulse representative of the pulse output. The optical detector is configured to detect the pulse output via an optical port of the electricity meter. The frequency counter is operably coupled to receive from the optical detector a signal that is representative of the detected pulse output.