Coaxial microcalorimeter - National standard for microwave power up to 18 GHz at NPLI

National Physical Laboratory India (NPLI) is the premier research and development centre and the National Metrology Institute (NMI), which provides apex level calibration services to the country. The coaxial microcalorimeter is used for assigning the effective efficiency of the reference standard coaxial thermistor mount in the frequency range 10 MHz-18 GHz. Measurement technique for calibrating microwave power reference standard has been presented. The calibration results and the various factors influencing the results have been explained. All the measurements are performed using a fully automated data acquisition system, which has been developed indigenously in the laboratory. The uncertainty components in assigning the effective efficiency. using calorimeter system have been discussed. The calibration uncertainty; which is a function of frequency ranges from 0.2 per cent at 10 MHz to 0.7 per cent at 18 GH