Abstract: In a watt-hour meter for metering electricity consumption of the type including: a disc mounted to a rotation shaft and a register mechanism. The watt-hour meter is further provided with a reading device including a light source creating a light beam; a light detector; a light interrupting device mounted on the shaft of the disc; a pulse meter and a protective cover; wherein the light source and light detector are protected from outside light, which may influence the reading of the pulse meter, by the protective cover. This reading device may be coupled to a data transmission line via a data recorder to allow remote reading of the electricity consumption.