Study on Primary Standard Calibration Type-N Thermistor Mount at 1 0 MHz

To accurately measure the power meter output voltage when calibrating the effective efficiency of a Type-N thermistor mount using the NIM primary standard at 10 MHz, we propose connecting the voltmeter at the isolated end of the power meter. The NIM-IV power meter is used to connect a thermistor mount for DC substitution, with the substitution power calculated by measuring the power meter output voltage using a voltmeter connected to the voltage terminal of the power meter. For calibration at 10 MHz, due to leakage, the thermopile output behaves differently when the power meter output voltage is measured using 34420A and 34401A, respectively, resulting in different calculated effective efficiencies. We propose connecting a voltmeter at the isolated end of the power meter to measure the power meter output voltage without affecting the measurement results, greatly ensuring the accuracy of the primary standard calibration at 10 MHz.