Electronic volt-square-hour metering method and apparatus

An electronic meter for measuring volts-square-hours in an electrical system comprising:

• means for generating first and second analog signals, said signals being proportional to a voltage in said system, and said first analog signal being 180.degree. out-of-phase with respect to said second analog signal,
• means for generating a relatively high frequency triangular signal,
• a comparator, said triangular signal being coupled to one input of said comparator,
• switching means for selectively coupling one of said first and second analog signals to the other input of said comparator, the output of said comparator being a pulse width modulated signal having a pulse width proportional to the amplitude of the analog signal coupled to one input of said comparator,
• means for multiplying said pulse width modulated output signal of said comparator with a signal proportional to said voltage in said electrical system, the output of said multiplier having an amplitude proportional to the electrical voltage in said system and having a pulse width proportional to the amplitude of said electrical voltage in said electrical system, and
• an integrator, said integrator being connected to the output of said multiplier, the output of said integrator being proportional to volts-square-hours.

An electronic meter for measuring volts-square-hours in an electrical system comprising:

• means for generating first and second analog signals, said signals being proportional to a voltage in said system, and said first analog signal being 180.degree. out-of-phase with respect to said second analog signal,
• means for generating a relatively high frequency triangular signal,
• a comparator, said triangular signal being coupled to one input of said comparator,
• switching means for selectively coupling one of said first and second analog signals to the other input of said comparator, the output of said comparator being a pulse width modulated signal having a pulse width proportional to the amplitude of the analog signal coupled to one input of said comparator,
• means for multiplying said pulse width modulated output signal of said comparator with a signal proportional to said voltage in said electrical system, the output of said multiplier having an amplitude proportional to the electrical voltage in said system and having a pulse width proportional to the amplitude of said electrical voltage in said electrical system, and
• an integrator, said integrator being connected to the output of said multiplier, the output of said integrator being proportional to volts-square-hours,
• a pulse generating circuit, the input of said converter being connected to said integrator to thereby convert the output of said integrator to a pulse train having each pulse proportional to volts-square-hours, wherein said switching means for selectively connecting said first or second analog signals to said comparator is driven by the output of said pulse generating circuit to thereby invert the analog signal coupled to said comparator every nth time a pulse is generated by said pulse generating circuit, said phase inversion causing said integrator to integrate in the opposite direction each time said nth pulse is generated to thereby correct offset integration errors in said meter.