In a zigzag running warning system for automotive vehicles which detects and gives a warning of zigzag running of a vehicle, a terrestrial magnetism sensor generates an electric signal having an amplitude varying in dependence on the direction of travel of the vehicle with respect to the direction of the terrestrial magnetism. An electronic unit in the system discriminates that vehicle is running in a zigzag direction when the amplitude of the electric signals changes in excess of a predetermined value at a period which is less than a predetermined time, and informs the driver of the zigzag running by a speaker, lamp or the like.

The present invention relates to an autonomous device which is intended to be carried by a tire and wheel assembly in order to detect revolutions of said assembly, comprising at least one sensor which produces signals and an interpreter device which is connected to the sensor in order to interpret the signals produced by the sensor. The sensor is a passive sensor, the produced signals of which are proportional to the temporal variations of a magnetic flux though this sensor, and is intended to be integral in rotation with the tire such that the revolutions of said assembly correspond to the revolutions of said sensor. The invention likewise relates to an assembly provided with an autonomous device which permits detection of revolutions of the assembly, and a method for detecting revolutions of the assembly.

A vehicle tachometer kit including a pick up coil that is adapted to be mounted on the outside of the vehicle's alternator to sense its rotating field without any disassembly. An induced signal in the coil from alternator field leakage provides the normal input to a user calibrated r.p.m. display driving circuit in the tachometer that can be calibrated for different alternators and drive pulley ratios without another tachometer by selectively applying a simulated input reference signal to the display driving circuit and adjusting the r.p.m. display until a scheduled ratio is achieved between the displayed r.p.m. and the reference signal.

A flow metering device includes a very sensitive sensor and detection unit for accurately measuring the flow of fluids such as water through a meter housing. At least two excitation windings are wound around a toroidal core of magnetic material having a non-linear characteristic. The excitation windings are connected in series to an AC source in such a way that the magnetic effects of the windings are additive. A pair of pickup windings are also wound around the core but in series-opposition fashion. The output of the pickup windings is fed to a detector unit including a negative feedback amplifier, rectifier diodes and a summing network. The apparatus is so sensitive that it can accurately detect the movement of an internal magnetic rotor through the rotor housing while rejecting other sources of possible interference.

A method of determining the angular position, rotational speed, and/or acceleration of a rotatable member, including: providing on the rotatable member an annular magnetic source generating tangential, radial, and axial magnetic flux field components; detecting, with a directional magnetometer having a toroidal core and two secondary output windings thereon, at a location radially spaced from the magnetic source, in proximity to the magnetic source, the amplitude(s) and/or change of amplitude(s) of one or more of the magnetic flux field components, and providing outputs indicative thereof; modifying the outputs, to equalize measured peak amplitudes of the magnetic flux field components and/or to compensate for environmental distortion thereof, by one or more methods selected from the group consisting of: (1) orienting the toroidal core such that the toroidal core lies in a plane at an angle between the plane of the annular magnetic source and a plane perpendicular to the plane of the annular magnetic source, (2) providing the secondary output windings with unequal numbers of turns, and (3) attentuating one of the outputs; and determining from the outputs the angular position, rotational speed, and/or acceleration of the rotatable member.