A. Ratio Calibration of Inductive Voltage Divider
The type of inductive voltage divider used in double voltage method is FG-B1 type and compose with ten equal division windings by dual-core and self-coupling structure. Its maximum output voltage is 1 kV and the no-load accuracy of the voltage ratio is better than 1×10-6. Because of that the accuracy of FG-B1 is defined in situation of no-load. So its voltage ratio must be calibration when it takes the load that is especially 10 nF capacitor. When the fifth ratio end and tenth ratio end of the inductive voltage divider all take the 10 nF capacitor load, use the relative calibrating method [5] can measure the ratio error of the fifth end and tenth end. The result is shown in Table 1.