Electronic watthour meter

In an electronic digital electricity meter having at least one line current sensor and at least one phase voltage sensor for providing samples of analog current and voltage signals to current and voltage analog to digital converters, respectively, whereby the analog current and voltage signals are converted to digital current and voltage words, respectively, for transfer to a digital signal processor for processing the current and voltage words and generating output pulses proportional to energy consumption, apparatus for self testing circuits and elements in said electronic digital electricity meter, comprising:

• (a) means for generating a self check enable signal for enabling said electronic digital electricity meter to perform self check operations;
• (b) means, responsive to said self check enable signal, for effecting the generation of a current test fail signal if the current sensor fails to pass an analog current signal;
• (c) means, responsive to said self check enable signal, for providing a voltage test signal of a prescribed level to each of said current and voltage analog to digital converters for conversion thereby to current and voltage words and processing int he digital signal processor to effect the generation of output pulses therefrom;
• (d) means, in communication with the voltage analog to digital converter, for generating a voltage test fail signal if the voltage phase sensor fails to pass a voltage signal of a prescribed magnitude to the voltage analog to digital converter while performing self check operations;
• and
• (e) means, for receiving the output pulses from the digital signal processor and responsive to said self check enable signal, for generating a digital signal processor fail signal if the processor fails to generate a prescribed number of output pulses within a prescribed period f time following the generation of said self check enable signal.

Apparatus, comprising:

• metering means for measuring energy consumed by an end-user and supplied from a power delivery system, said metering means comprising signal processing means, sensor means for sensing signals from a power line forming part of the power delivery system and, analog-to-digital converter means, outputs of said sensor means being coupled to said converter means, and outputs of said converter means being coupled to said signal processing means;
• means for testing operation of said metering means, aid testing means comprising first means for applying a first test signal to said sensor means and second means for applying a second test signal to said converter means so that the second test signal is converted to a digital word, said signal processor means being configured to process the digital word from said converter means to effect the generation of output pulses representative of the second test signal;
• and
• means for indicating a metering means failure, said indicating means comprising means for generating a sensor fail signal if said sensor means fails to generate a first test response signal subsequent to application of the first test signal, and means for generating a signal processor fail signal if said processing means fails to generate a second test response signal subsequent to application of the second test signal to said converter means.