Abstract: A three-phase toroidal current transducer comprises a cuboid detector body (12), having three cylindrical passages (14) each for receiving a single-phase cable of a three-phase load (not shown). Each of the three passages (14) has an embedded toroidal winding (not shown) which is used to detect a current in the load cable (also not shown). Signals representing the current in each of the three individual load cables are sent to a meter (not shown), which may be located remotely. The signals are transmitted along a multi-core signal cable (16), which has a standard connector (18) for a plug-in connection to the meter. One of the wires in the multi-core signal cable (16) is connected to a component in the transducer (10) that identifies the rating of the transducer, so that the meter can determine this automatically when the signal cable is plugged in.

Abstract: In a voltage measurement apparatus high—i.e. un-attenuated—voltages are connected to an attenuator 12, which then feeds attenuated voltage waveforms to a microprocessor-based analogue-digital converter/voltage measurement circuit 14. A representative digital voltage signal 16 and a synchronising signal 18 are then sent across an optical isolation barrier 20, and are then output to metering circuits 22. The metering circuits 22 receive analogue current inputs 24 which are sampled in synchronism with the digital voltage signals for an accurate measurement of power. Safe outputs 26 are provided which are isolated from any dangerous voltage.

Abstract: A modular metering unit, shown generally at 10, comprises a master module 12, slave modules 14a to 14f, and a communications module 16. Together the modules 12, 14 and 16 make up a modular metering unit for metering electricity from plural Loads (not shown) such as, in the case of a large food retail premises, chill or freeze display cabinets. Each of the slave modules includes electricity meters for measuring electricity supplied to a load. The loads may be located remotely from the metering unit and each one has a current detector that feeds a low-voltage signal back to the meter via a cable (not shown). The slave modules are connected to one another and to the master module by an internal bus through which data and power are carried between the modules.