-The functional characteristic of LISN circuit, which is used for measurements of conductive noise in mains power line, is basically related to frequency characteristics of passive elements like inductors used in the circuit as well as the frequency response of inductors is highly related to the resins used in the varnishing process. The significant problem in determination of an inductor's frequency characteristic is the intrinsic resistance, inductance and parasitic capacitance. In this triplet, the parasitic capacitance is the major limiting factor of inductor's frequency range. This capacitance depends on inductor design parameters and materials filling the spaces of coil like resin and its coherency after curing process. In this paper, two similar inductors were designed and built. The first inductor was not varnished while the second one was varnished with VPI technology. VPI, or Vacuum, Pressure, Impregnation technology is one of the most reliable methods performing good insulating conditions for electrical circuits and windings based on resins. The measured results show that implying varnishing technology does not significantly affect the frequency response. However, due to mechanical solidity aspects and improved environmental protection, it is better to varnish the inductors.
A scanning force microscope combining commercial AFM probes, printed circuit boards, and electrostatic actuation and detection is proposed and demonstrated. The electrostatic actuator is formed by the AFM probe and a fixed trace on a PCB. It is driven by a biased harmonic voltage with a frequency close to the probe’s resonant frequency. The separation distance between the probe tip and the specimen surface is managed to perform tapping mode scanning. A lock-in amplifier measures the second harmonic of the actuator current as the sense signal in an open-loop scheme. Preliminary results produced by the current’s magnitude and phase resemble the specimen’s topography.
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