Patent ID: 6922643

Claim:
A monitoring apparatus which performs a measurement of a leakage current or a resistance of a target measurement circuit and which performs arithmetic processing on the basis of said measurement, comprising: an input unit configured to receive an output of a current transformer from which said measurement of said leakage current is taken; an A/D converter unit operable to convert an output of said input unit to produce a digital value; a memory unit which stores said digital value; an arithmetic processing unit operable to calculate said leakage current, the arithmetic processing unit configured to receive a leakage current signal and a voltage signal from said target measurement circuit and further configured to sample one cycle of a waveform of said leakage current signal and of said voltage signal and to compute a resistance component current by dividing the average of an integrated value of instantaneous values of said voltage signal and instantaneous values of said leakage current signal by the square root of the average of instantaneous values of said voltage signal; an output unit which supplies an arithmetic result of said arithmetic processing unit; a terminal table configured to connect a current signal line and a voltage signal line extending from a current transformer; a setting unit which sets a current transforming ratio of said current transformer and selects a plurality of inputs, and switches a display type; and a display unit which displays set values of said setting unit and said arithmetic processing result of said arithmetic processing unit, wherein said monitoring apparatus has one side of about 200 mm and another side of about 150 to 200 mm in appearance.