Abstract: An apparatus and method for detecting defects in moving parts having a central rotating shaft, in particular shaft bearings, with the aid of an acoustic-electric transducer converting the mechanical acoustic vibrations received into electric signals to be processed in a signal processing circuit to signals indicative of the status of the parts, the improvement wherein the acoustic-electric transducer is centrally disposed on one end of the shaft so that it rotates therewith and receives vibrations therefrom, and wherein the acoustic-electric transducer comprises a piezoelectric element, and an amplifier having its control terminal coupled to the pass filter.

Abstract: A device for measuring the effective viscosity of a lubricant in which a motor rotates one element of a bearing with respect to the other, the lubricant being supplied to the bearing. The bearing is part of a sensor that outputs a signal corresponding to the percentage of contact time between the elements of the bearing. A speed regulator for the motor is responsive to the output of the sensor to maintain the speed of relative movement so that no roughness contacts occur in the bearing, at which time the motor speed is a measure of viscosity.

Abstract: A method for detecting faults or defects in moving machine parts wherein mechanical vibrations produced by a fault or defect are converted into an electrical signal from which the condition of the machine part is obtained. For converting the mechanical vibrations into an electrical signal, an acoustic-emission transducer with wide bandwidth is used. A frequency range in the electrical signal is selected where the half wavelength is smaller than the smallest linear dimension of the cross section of the transducer face which is in contact with the machine part.

Abstract: Means for determining the state of lubrication in surfaces lubricated by a lubricant and rolling or sliding with respect to one another, provided with a unit for generating a signal dependent upon the capacitance between the lubricated surfaces, characterized by an operating circuit connected to the unit which, in response to the signal dependent upon the capacitance, emits a second signal which is dependent in accordance with a non-linear, for example, exponential, function upon the capacitance between the lubricated surfaces such as that one and the same relative variation in the thickness of the lubricant between the lubricated surfaces results in a fairly great signal variation in the event of decreasing thickness, the second signal being supplied to an integrator which integrates the second signal over an integration period displaced in time and the output signal of which indicates the state of lubrication.

Abstract: A system for measuring the variation in the capacitance of a bearing installed on a shaft in a housing. It is shown to include an electrically conductive measuring ring interposed between the bearing and the housing, an insulating layer surrounding the measuring ring wherein the insulating layer between the bearing and the measuring ring is considerably thinner than the remaining portion of the insulating layer, and measuring means connected to the measuring ring and the shaft to measure the variations in the capacitance of the bearing. In such a system, capacitance measurements are made without significant interference from the capacitance existing between the housing and the shaft.

Abstract: The invention relates to a device for measuring the variation of a capacitive impedance, the dielectric of which consists of a lubricant, provided with an oscillator that supplies a signal having a predetermined frequency to the capacitive impedance by way of a bias impedance.The device according to the invention is characterized by a current measuring means delivering a signal depending on the current passing through the capacitive impedance to a converter the output of which delivers a direct current voltage signal coinciding with the instantaneous value of the capacitive impedance.

Abstract: A device for measuring the lubrication of surfaces which roll or slide relative to one another and are lubricated by a lubricant. The device includes an oscillator generating an AC voltage signal whereby the capacitance between the lubricated surface is measured by first grounding the capacitance and then connecting it by way of a condenser to the output of an oscillator. This output is connected further to a first input of a modulating circuit while the voltage occurring across the capacitance is delivered to a second input of the demodulating circuit. The output of the demodulating circuit is connected to a processing unit which derives a signal corresponding to the thickness of the lubricant film as well as the percentage contact time during a certain interval of measurement from the output signal of the demodulating circuit.