An Adjustable Extremely Low Frequency Electromagnetic Field Generator

The risk effect of long-term occupational exposure to extremely low-frequencyelectromagnetic fields (ELF-EMFs) has been studied extensively. However,due to several experimental issues such as exposure measurement error and thelack of standard ELF-EMFs exposing devices, the obtained results are controversial.The inconsistent reported results preclude clear conclusions on the evidenceof an association between EMF exposure and the disorders reported. To assist withresolving these issues, a digital–low cost ELF-EMFs generator to produce EMFswith desired magnitude and frequency is proposed. A sinusoidal waveform with adjustable amplitude and frequency controlledby a microprocessor is generated and then is applied to a coil with a U-shapecore. To increase the accuracy of the instrument, three coils with 250 turns; 500turns; and 1200 turns were designed and used in the instrument. The amplitude andfrequency of the voltage delivered to each of these coil are controlled by turningoff and on TRIAC transistors controlled by a microprocessor–based system. The designed instrument provided EMF with magnitude of 0.55 mTeslato 1.56 mTesla with error rate < 5.9% and frequency of 10 Hz to 50 Hz with errorrate <1%. The provided EMF was sufficiently homogeneous over a given volumeand was stable over time. The quantitative and qualitative experimental results showed that the designedinstrument is reliable and accurate to be used in research laboratories for furtherinvestigation of the health effect of long-term occupational exposure to ELF-EMFs.