Polyphase electric energy meter

Abstract

A polyphase electric energy meter comprises a microcontroller with a front end that converts analog current input signals and analog voltage input signals to digital current and voltage samples for processing by the microcontroller. The front end includes separate input channels, each for one of the current input signals with a sigma-delta modulator followed by a decimation filter. The front end further includes a common input channel for all voltage input signals with a multiplexer, an analog-to-digital converter and a de-multiplexer. The separate input channels and the common input channel provide the digital current and voltage samples for processing by the microcontroller.

1 - 6 . (canceled) 
   
   
       7 . A polyphase analog front end comprising:
 a plurality of programmable gain amplifiers (PGA), wherein each PGA is adapted to receive a current signal;   a multiplexer that is adapted to receive a plurality of voltage signals;   a plurality of sigma-delta modulators, wherein each sigma-delta modulator is coupled to at least one of the PGAs;   an analog-to-digital converter (ADC) that is coupled to the multiplexer; and   a synchronizer that is coupled to each of the sigma-delta modulators and to the ADC.   
   
   
       8 . The polyphase analog front end of  claim 7 , wherein the polyphase analog front end further comprises a decimation filter that is coupled to each sigma-delta modulator. 
   
   
       9 . The polyphase analog front end of  claim 7 , wherein the polyphase analog front end further comprises a demultiplexer that is coupled to the ADC. 
   
   
       10 . A system comprising:
 a source having a plurality of phases;   a load that is coupled to each phase of the source;   a plurality of current transformers, wherein each transformer is coupled to at least one of the phases;   a plurality of voltage dividers, wherein each voltage divider is coupled to at least one of the phases;   a microcontroller having an analog front end, wherein the analog front end includes:
 a plurality of programmable gain amplifiers (PGA), wherein each PGA is coupled to at least one of the transformers; 
 a multiplexer that is coupled to each of the voltage dividers; 
 a plurality of sigma-delta modulators, wherein each sigma-delta modulator is coupled to at least one of the PGAs; 
 an analog-to-digital converter (ADC) that is coupled to the multiplexer; and 
 a synchronizer that is coupled to each of the sigma-delta modulators and to the ADC. 
   
   
   
       11 . The system of  claim 10 , wherein the system further comprises a decimation filter that is coupled to each sigma-delta modulator. 
   
   
       12 . The system of  claim 10 , wherein the system further comprises a demultiplexer that is coupled to the ADC.