In the modern world we are surrounded by various electro-magnetic emissions of radio and tv transmitting stations, cellphone towers, home appliances and so on. Measurements of different electronic appliances were made using electro-magnetic meter. Schematic of meter works as follows, electro-magnetic radiation induces voltage in the coil, it gets amplified by op-amp, so we can read it on digital voltage meter. Measurements are in conditional units, used to compare.
TV Dryer machine