Calibration of commercial power density meters at RF and microwave frequencies

A calibration of 73 different probes from three different manufacturers has been carried out at 27 and 2450 MHz, respectively. The power density levels used were in the range 10-100 W/m². The investigation was carried out at the Swedish National Primary Calibration Center, whose standards are traceable to the National Bureau of Standards, USA. The total uncertainty in the measurements is estimated to be ±0.7 dB for both 27 and 2450 MHz. Of the total number of instruments tested in this study, 5% did not work at all, although their owners thought they did. The results point to the necessity of a regular and relatively frequent calibration of the instruments to be used for monitoring of potentially hazardous electromagnetic fields.