As the measure error of the whole measure system is only come from the bridge and the inductive voltage divider. The voltage ratio error is always better than 1×10-6, the measurement error of the bridge will cumulative increase when uses multiplicative way to calculate the voltage coefficient value. And the process of linear fit is exist error too. So can consider error of whole system is mainly about the accuracy of the bridge when ignore the error of linear fit. From Fig.5 and Fig.4 can get the voltage coefficient value of 30V are respectively 4.46×10-6 and 3.91×10-6. So, the error of whole system is 5×10-7.