Poly-phase electric energy meter
View Patent ↗A poly-phase electric energy meter comprises a front-end that converts analog current input signals and analog voltage input signals to digital current and voltage samples and a micro-controller for computing power consumed. The front end includes first and second input channels. Each input channel has a multiplexer, an analog-digital converter, a de-multiplexer and a set of data registers. The first input channel receives current input and the second input channel receives voltage inputs. A multiplexer control causes the first and second channels to sequentially sample the current and voltage for one phase at a time and store digital data in corresponding data registers. The micro-controller computes energy consumed from the simultaneous current and voltage samples.
1. An electric energy meter for poly-phase electricity comprising:
a front-end circuit including
a first input channel having
a first multiplexer having a plurality of inputs, each input connected to a current transformer of a corresponding one of the phases of the poly-phase electricity, an output and a selection input, said first multiplexer selectively connecting one input to said output dependent upon said selection input,
a first analog-digital converter having an input connected to said output of said first multiplexer and an output, said first analog-digital converter generating a digital output corresponding to an analog signal at said input,
a first de-multiplexer having an input connected to said output of said first analog-to-digital converter, a plurality of outputs and a selection input, said first de-multiplexer connecting said input to one of said outputs dependent upon said selection input, and
a plurality of first data registers, each data register connected to a corresponding output of said first de-multiplexer for storing said corresponding de-multiplexer output;
a second input channel having
a second multiplexer having a plurality of inputs, each input connected to a voltage divider of a corresponding one of the phases of the poly-phase electricity, an output and a selection input, said second multiplexer selectively connecting one input to said output dependent upon said selection input,
a second analog-digital converter having an input connected to said output of said second multiplexer and an output, said second analog-digital converter generating a digital output corresponding to an analog signal at said input,
a second de-multiplexer having an input connected to said output of said second analog-to-digital converter, a plurality of outputs and a selection input, said second de-multiplexer connecting said input to one of said outputs dependent upon said selection input, and
a plurality of second data registers, each data register connected to a corresponding output of said second de-multiplexer for storing said corresponding de-multiplexer output;
a multiplexer control connected to said selection inputs of said first and second multiplexers and said first and second de-multiplexers, said multiplexer control supplying said selection inputs of said first and second multiplexers to synchronously select signals corresponding to the same phase of the poly-phase electricity, and said multiplexer control supplying said selection inputs of said first and second de-multiplexers to sequentially store digital samples corresponding to each phase of the poly-phase electricity in corresponding data registers; and
a micro-controller operable to access data in said first and second data registers and computer electric power consumed.
2. The electric energy meter according to claim 1 , wherein:
said second multiplexer further includes at least one additional input for an analog auxiliary input signal;
said second de-multiplexer further includes at least one additional output for said auxiliary input signal;
said second data registers further include at an additional data register connected to each additional output of said second de-multiplexer; and
said multiplexer control further supplying selection inputs to said second multiplexer and said second de-multiplexer to sample each analog auxiliary input signal and store a corresponding digital auxiliary input signal in a corresponding second data register.
3. The electric energy meter according to claim 1 , wherein:
said first multiplexer further includes at least one additional input for an analog auxiliary input signal;
said first de-multiplexer further includes at least one additional output for said auxiliary input signal;
said first data registers further include at an additional data register connected to each additional output of said first de-multiplexer; and
said multiplexer control further supplying selection inputs to said first multiplexer and said first de-multiplexer to sample each analog auxiliary input signal and store a corresponding digital auxiliary input signal in a corresponding first data register.
4. The electric energy meter according to claim 1 , wherein:
said micro-controller computes computer electric power consumed by
recalling digital current data from one of said first data registers,
recalling digital voltage data from one of said second data registers corresponding to the same phase of the poly-phase electricity as said recalled digital current data,
multiplying said recalled digital current data and said recalled digital voltage data thereby producing a power product, and
accumulating said power products over time.