Magnetic anomaly detection (MAD) is a passive method used to detect visually obscured ferromagnetic objects by revealing the anomalies in the ambient Earth magnetic field. In this paper, we propose a method for MAD employing the high-order crossing (HOC) approach, which relies on the magnetic background nature. HOC is an alternative method for spectral analysis using zero-crossing count, also enabling signal discrimination. Tests with real-world recorded magnetic signals show high detection probability even for low signal-to-noise ratio. The high detection probability, together with a simple implementation and low power consumption, makes the HOC method attractive for real-time MAD applications such as intruder detection and for research on an earthquake magnetic precursor.

A new method of constructing phase-lock loop systems with wide capture range and fast response is suggested. The suggested systems employ the relatively well-known double-loop configuration. They are unusual in the sense that the two multipliers (phase detectors) are replaced by one divider.

This letter suggests a simple method for regulating the terminal voltages of a laboratory synchronous generator system. The regulation effect is achieved by relatively simple means with no need of building extra networks. The system as a whole should be helpful in experimenting with synchronous generators in relatively small laboratories. The letter includes experimental results and a block diagram of the regulation system.

A major improvement in the sensitivity of an eddy-current sensor is described. This was achieved as a result of internal noise reduction by a supplementary heat treatment of the ferromagnetic core. Its present sensitivity of 0.1 nT and its simple construction make this eddy-current magnetometer a real competitor with other similar devices, e.g., the flux-gate magnetometer.

A new dc and low-frequency magnetic field sensor based on multifield eddy-current effects is described. Like the fluxgate magnetometer, it uses nonlinear ferromagnetic materials but possesses advantages due to the utilization of eddy currents. DC and low-frequency ac fields with intensities of about 1 γ have been measured with a simple experimental arrangement.