Abstract: A matching amplifier for an induction probe which detects low-frequency alternating magnetic fields of floating bodies propagating in water. The matching amplifier has an isolating amplifier and a frequency response-determining network, with the network being provided with a frequency pass region having a band-pass characteristic and an integrating response in the band pass for the purpose of canceling the decorrelation of the measuring values emitted by the induction probe, with the integrating response being matched to compensate for the decorrelation of the measuring signal of the induction probe generated by the differentiating effect of the induction probe.

Abstract: A probe for the detection of alternating magnetic fields has a highly permeable probe core (10) and a measuring winding (11) surrounding the probe core, with the measuring winding being put together of several coils (111, 112, 113) which are connected in series. In order to produce a probe which is suitable for the detection of extremely low-frequency alternating magnetic fields from a minimum distance commonly required for the detection of floating bodies that emit such alternating fields, the probe core (10) is put together from flat strips (16) of amorphous or microcrystalline magnetizable material with insulating strips (17) disposed in-between. The coils of the measuring winding (11) are configured as self-supporting coils, preferably as self-bonding wire coils, and surround the probe core (10) with almost no clearance.

Abstract: An apparatus for measuring the winding temperature of electric machines uses an a.c. reference voltage source generating an a.c. reference voltage with a predetermined, non-line frequency, preferably below 10 Hz., a current detector detecting the current generated from the a.c. reference voltage and/or the a.c. reference voltage directly, and a measuring and evaluating device measuring the current to determine the winding temperature. The a.c. reference voltage is added geometrically to the line voltage and generates a current proportional to the winding conductance which is temperature dependent.

Abstract: An arrangement for measuring the slip of electric induction motors determines the relative measure of the difference between rotary field speed and rotor speed of induction motors by utilizing the nonlinearity effects of the magnetization characteristics of ferromagnetic materials. Slip-proportional current and/or voltage signals are detected at the terminals of the induction motor. By suitable processing of these slip-proportional signals, such as frequency conversion and filtering, a frequency-proportional measure of the slip is provided which is then subjectable to measuring or further processing.

Abstract: The invention relates to a configuration for rapid detection of short-circuits and for generating an electrical trigger command with an electronic measuring and processing configuration for current values, which compared in a digital comparison circuit with predetermined limit values transmits the trigger command. The measuring configuration determines the current over time as well as the voltage of the grid and the resulting complex impedances and power. In addition to segmentation, standardization and scaling of the current and voltage values, a cross correlation function as well as the respective product and quotient of the Fourier transforms of the voltage and the current for frequency ranges associated with each other are determined, so that a respective power and impedance spectrum are obtained for evaluating the state of the installation.