Usage monitoring apparatus

An apparatus is disclosed for monitoring usage of multiple electrical devices. The apparatus comprises multiple non-invasive current sensors for sensing current in respective conductors associated with the electrical devices. Such conductors may for example be the electrical power supply leads to the devices. The apparatus further includes multiple analogue to digital conversion functions for digitizing the output from the respective current sensors. A microprocessor is arranged to receive the digitized current sensor and is programmed to create usage data relating to the respective electrical devices. Such usage data may include cumulative elapsed running time. The microprocessor has an associated memory in which the usage data is stored in association with corresponding data identifying the electrical devices. The system further includes an interface through which the usage and identifier data are extractable, to provide usage information for the respective electrical devices. The apparatus may be divided into two separate sub-systems connected through a bus and it is particularly preferred that a sub-system incorporating the current sensors is mounted to, or otherwise associated with, a power distribution unit.