Master metering module with voltage selector

A voltage monitor means of the kind which provides an indication output signal which is related to the potential difference between a first line voltage and either a second line voltage or neutral when present, comprising:

• indicating means having an input terminal and an output for providing said indication;
• terminal means for receiving said first line voltage, said second line voltage and said neutral when present;
• microprocessor controlled switch means having an output terminal and first and second switch means input terminals, said first switch means input terminal being connected to said second line voltage at said terminal means and said second switch means input terminal being connected to said neutral when present at said terminal means, said microprocessor controlled switch means also having a control terminal which is utilized to connect said first and said second switch means input terminal to said output terminal of said switch means;
• differential means having an output terminal which is connected to said input terminal of said indicating means and having a pair of input terminals for being interconnected at one of said pair of input terminals to said first line voltage at said terminal means and for being interconnected at said other of said pair of input terminals to said output terminal of said microprocessor controlled switch means;
• and
• first programmable means for being actuated to indicate if a neutral is present;
• second programmable means for being actuated to indicate if line-to-line voltage is desired;
• microprocessor means connected to said control terminal of said switch means, said first programmable means and said second programmable means for being conditioned to provide a control signal to said microprocessor controlled switch means for interconnecting said first switch means input terminal to said output terminal thereof when said first programmable means indicates a neutral is not present or when said first programmable means indicates a neutral is present and said second programmable means indicates line-to-line voltage is desired or for interconnecting said second switch means input terminal to said output terminal when said first programmable means indicates a neutral is present and said second programmable means indicates line-to-line voltage is not desired, so that the output terminal of said differential means provides a signal to said indicating means so that said indicating means provides said indication which indication is related to the difference between said first line voltage and said second line voltage or the difference between said first line voltage and neutral when present depending upon the condition of said microprocessor means.