Linear alternating current interface for electronic meters
US5696441A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 13, 1994 |
| Grant date | Dec 9, 1997 |
| Priority date | — |
| Expiry date | May 13, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R15/18
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An interface circuit (10) for use with electronic metering equipment (E) to provide a linear output response to an AC or analog input. An air core transformer (12) has a first coil or winding (12a) connected to a load (L). An AC current I.sub.LOAD is produced by the load and is coupled to a secondary coil or winding (12b) of the transformer. The transformer has an air core rather than a ferromagnetic core so to have no saturable core. Because no load is drawn by transformer coil, the voltage across a terminal of the coil equals the EMF induced in the coil. The EMF, in turn, equals the mutual inductance of the coils multiplied by the rate of change of magnetic flux linkages over time. The output from the transformer is applied as an input to an operational-amplifier (16) which has a high input impedance. Further, the amplifier is a low drift amplifier which performs a linear amplification of the input signal provided thereto. In certain embodiments, a pair of similar amplifiers are used and the secondary winding of the transformer is a tapped winding so to accommodate both a low range and a separate high range of inputs. The output from the operational amplifier is supplied to an an…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.