Research on the calibration technology of direct current sensor based on the difference measurement principle

Direct current sensor converts the input current into a proportional output current. The ratio error is an essential specification, the error value determination is one of the key links in the rational use of direct current sensor. The specification of commercial instruments employed in the traditional source meter method failes to meet the calibration requirements of high accuracy direct current sensor(maximum permissible error 10^-5 magnitude and above). A principle based on the measurement of secondary side difference current is proposed. According to the characteristics of the calibrated ratio parameters,taking the standard direct current ratio value as the reference,the actual value and error of direct current ratio are obtained by employing self-calibration method,equal-ratio calibration method and stage-connection equal-ratio calibration method. This measurement principle reduces the index limit of instrument and the uncertainty at the same time; satisfies the calibration requirements of direct current ratio instruments.