Noninvasive measurement of current in the human body for electromagnetic dosimetry

Minimally perturbing, resistive, nonferrous probes were developed for noninvasively measuring hazardous currents induced in the human body by electromagnetic fields at 1 to 200 MHz. Each probe has a resistive toroidal coil that is placed around the leg or other body member. An electrostatic shield is required to limit capacitive coupling. A new shielded test fixture provides TEM fields for calibration with a VSWR less than 1.1 from 1 to 200 MHz. A man-sized phantom was exposed to the near-field of a vertical monopole antenna at 29.9 MHz, and the value of the current measured in the leg with our probe is in reasonable agreement with measured heating. Analyses and experiments show that commercial ferrous current probes modify the circuit in which they are used, changing the current being measured. Less change is caused by our nonferrous current probes.