An Adjustable Extremely Low Frequency Electromagnetic Field Generator

Purpose: The risk effect of long-term occupational exposure to extremely low- frequency electromagnetic fields (ELF-EMFs) has been studied extensively. However, due to several experimental issues such as exposure measurement error and the lack of standard ELF-EMFs exposing devices, the obtained results are controversial. The inconsistent reported results preclude clear conclusions on the evidence of an association between EMF exposure and the disorders reported. To assist with resolving these issues, a digital–low cost ELF-EMFs generator to produce EMFs with desired magnitude and frequency is proposed. Methods: A sinusoidal waveform with adjustable amplitude and frequency controlled by a microprocessor is generated and then is applied to a coil with a U-shape core. To increase the accuracy of the instrument, three coils with 250 turns; 500 turns; and 1200 turns were designed and used in the instrument. The amplitude and frequency of the voltage delivered to each of these coil are controlled by turning off and on TRIAC transistors controlled by a microprocessor–based system. Results: The designed instrument provided EMF with magnitude of 0.55 mTesla to 1.56 mTesla with error rate < 5.9% and frequency of 10 Hz to 50 Hz with error rate <1%. The provided EMF was sufficiently homogeneous over a given volume and was stable over time.