Current measurement transducer with digital output - is suitable for digital wattmeters and uses current feedback comparison technique

摘要

A current transducer produces a digital output which can represent instantaneous current. It is suitable for use in digital wattmeters and other applications. A current feedback and comparison technique is used, to achieve accurate results. A current transformer with three windings (1-3) is used in the basic transducer. The current to be measured is passed through one winding (1) and the flux produced by this in the transformer core (5) is offset by the current in a secondary winding (2). The difference is represent by a voltage in the third winding (3), which is amplified (6) and converted to digital form (7, 8) to provide the required digital output. The same output is fed back through a D-A converter (10) and amplifier to provide the flux offset current. Together with a digital voltage measurement this arrangement may be used in a digital wattmeter.