| 摘要 |
PROBLEM TO BE SOLVED: To enable highly accurate measurement without inducing large increase in a device cost nor requiring a surplus work of an inspector even when a capacity such as a Y capacitor and the like affecting measurement is unknown.SOLUTION: A reference resistor Rref having a resistance value known is connected to power source lines 111, 112 and the like to implement a test mode. In the test mode, on the basis of the resistance value of the reference resistor Rref, an appropriate calculating formula or an appropriate capacity parameter is automatically grasped by a microcomputer 11. In consideration to a capacity, the appropriate calculating formula automatically selected from a plurality of calculating formulas or the appropriate capacity parameter is used to reduce a calculation error of a ground resistance value. A conversion map equivalent to the calculating formula is used. On the basis of the calculation error of the ground resistance value, an electrostatic capacity is calculated by a back calculation of the calculating formula. |
