Patent ID: 7525317
Filing Date: 2009-04-28
Classification: G01R

Abstract:
1. A ground resistance monitoring device for measuring ground resistances of a plurality of test ground points, comprising: a display and operation unit having at least a display and a keypad as a man-machine interface of said ground resistance monitoring device; a processing unit having two-way connection to the other units for exchanging data therebetween; a testing and power supply unit connected to a neutral lead, a power lead, and a ground lead of an AC mains for regulating and rectifying said AC power, and providing said regulated and rectified power to the other units of said ground resistance monitoring device, said testing and power supply unit capable of determining a grounding condition and obtaining a ground resistance of said ground lead of said AC mains, said testing and power supply unit providing an appropriate voltage source for measuring ground resistances of said test ground points; a measurement unit having a plurality of monitoring ports, each said monitoring port connected to a said test ground point through a conductive wires; wherein, under a monitoring mode of said ground resistance monitoring device, said processing unit periodically selects a said monitoring port and forms an electrical path from said voltage source, through said monitoring port, a said conductive wire connected to said monitoring port, a said test ground point connected to said conductive wire, to said ground lead of said AC mains via earth for obtaining a measurement result of a ground resistance of said test ground point, and said processing unit compares said measurement result to a safety range of said monitoring port and issues an alarm when said measurement result exceeds said safety range; and a second ground port, wherein, under a calibration mode of said ground resistance monitoring device, said processing unit selects a said monitoring port and forms an electrical path from said voltage source, through said monitoring port, a said conductive wire connected to said monitoring port, a said test ground point connected to said conductive wire, to said second ground port via a second conductive wire substantially identical to said conductive wire for obtaining a wire resistance of said conductive wire by dividing a second measurement result of said test ground point by two.