The review of techniques used for measurements of permittivity and permeability of materials for quasi-static electromagnetic field.
Measuring magnetic fields of equipment under test at low frequencies which is received by loop antennas using an EMI receiver with small bandwidths takes much time and can even reach a week for a standard measurement. This waste in time could be avoided by applying time domain measurements. Commercial time-domain EMI (TDEMI) measurement equipment are sampling at the intermediate frequency, and are still relatively expensive. Base-band sampling using low-cost digitizers, or an oscilloscope, is proposed in this paper. The measured data is converted to the typical results in frequency domain via fast Fourier transform, while the necessary large dynamic range is achieved via oversampling. This methodology decreases the cost of the test equipment, but most of all reduces the measurement time drastically compared to the classical frequency domain measurement approach. The setup is described. Measurements with a conventional receiver parallel to the digitizer using a signal generator powering a radiating loop have been performed. Also measurements on an actual interfering source with pulsed magnetic fields are performed. It is shown that the measurement results are the same, while the measurement time has been reduced drastically.
In modern buildings virtually all electric loads are non-linear. Neither the applicable standards for supply of electrical energy nor those for consumption of electrical energy take into account the replacement of linear loads by non-linear loads. Low power equipment is exempted in standards assuming that all other (linear) loads dominate the power quality. In modern buildings there is a huge number of non-linear loads in lighting, monitor, computer and small power supplies and only a very limited number (or no) conventional linear loads. This is causing unacceptable interference with costly consequences. This paper analyzes current standards and the (exemptions for) harmonic current consumption of modern devices. The increase in harmonic distortion in a new building due to a multitude of non-linear equipment is shown. This forced the owner of the building to make costly changes in the power supply network.
When testing large stationary equipment for EMC compliance, on-site testing is often the only option. In case of a fixed mains connection, use of an artificial mains network is problematic. Within In the framework of an European Research project on EMI testing of large installations, research has been performed on the performance of new and existing alternative methods. While researching existing solutions, several devices were found that served to monitor events on live mains connections. A lot of research is going on in the 2 to 150 kHz band as proper civil emission standards are lacking here and manufacturers apparently -deliberately-select the switching frequency of their power converters in this range in addition, most modern power input circuits are diode bridges followed by electrolytic capacitors, creating mains frequency synchronous interference. One of these methods involves using a high-pass filtered adapter using a commercially available common-mode coil as transformer to measure mains carried noise safely.
Conducted spurious phenomena cause interference in the power supply network of complex installations. The time dependent behaviour of these phenomena calls for dedicated measurement techniques in time domain. Quantities to measure are defined for DM as well as CM. Various measurement sensors are designed, implemented, characterised and tested. Frequency domain measurement equipment is not suitable for these time variant disturbances. Signal processing on the time domain data provides the necessary characteristics of the system. The proposed measurement methods provide a basis for the analysis of conducted behaviour of equipment as well as fixed installations.
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