Patent ID: 9671467
Date: 2017-06-06
CPC Classifications: G01R,G05B,G05F

Claim:
1. An electric power meter capable of monitoring a contact status of a latch relay, the electric power meter comprising: a latch relay having a pair of primary coils and a secondary contact, the secondary contact operable to a closed position where an electric power from an electric power source is supplied to an electric load, or an open position where power supply from the power source to the load side is interrupted, the primary coils configured to provide a magnetic force to open or close the secondary contact; and a meter controller connected to the latch relay, configured to compare an input voltage of the primary coils of the latch relay with an output voltage of the secondary contact of the latch relay, configured to determine that the latch relay is in a closed position when the input voltage of the primary coils is substantially equal to the output voltage of the secondary contact with a predetermined allowable error range, and configured to determine that the latch relay is in an open position when the output voltage of the secondary contact has not been input, even if the input voltage of the primary coils has been input.