An electromagnetic pickup has a coil and a core. A noise shielding cylindrical member of magnetic material is provided around the coil to form an open magnetic circuit between the noise shielding member and the core.

A dual magnetic sensor utilizing a pair of separate coils to generate separate and isolated signals from a single pickup point, each signal having a power output at least equal to that of a conventional single coil sensor, the dual sensor having physical dimensions making it substitutable for a conventional single coil sensor.

A dual speed sensor pickup assembly (140) for sensing the rotational velocity of two independently rotatable, closely axially spaced exciter rotors (116 and 118) is provided. The pickup assembly includes two speed sensor assemblies (136 and 138) each including a pole piece (152,160) having a longitudinal axis (152a,160a) with the longitudinal axes skewed relative to one another but radial relative to the common axes of rotation (24) of the exciter rotors. Each speed sensor includes a permanent magnet (154,162) disposed between an end of the pole piece (152,160) and having a face divided into first and second surfaces (154a,154b and 162a,162b) by a slot (154c,162c) therein. In one embodiment a primary coil (156,164) and a secondary or anti-cross talk coil (158,166) surrounds the pole piece of each sensor (136,138), and each secondary coil is conductively connected to the primary coil of the other sensor. In another embodiment, an electronic circuit (176) is provided for producing anti-cross talk signals which are added to the speed sensor signals.

This invention relates to a magnetic pick-up circuit for use in integrated drive generators of the type employed on board aircraft for power generation. Prior art magnetic pick-up circuits failed to compensate for interference due to operation within an ambient electromagnetic field or failed to preserve the ambient electromagnetic field. The magnetic pick-up circuit includes in combination a first coil responsive to an ambient electromagnetic field and a modulated flux field and a second coil responsive to the ambient electromagnetic field connected to the first coil in opposition to thereby insure that a signal induced by the ambient electromagnetic in the first coil is cancelled by a signal induced by the ambient electromagnetic field in the second coil. Means for providing an output signal representative of modulation of the modulated flux field are coupled to the first coil and the second coil. This output signal is free from distortion due to the ambient electromagnetic field.

A tachometer generator of the inductive pickup variety is disclosed, particularly adapted to be mounted in close proximity with a rotating multipole permanent magnet structure. The coil produces a voltage output proportional to the rate of change and magnitude of the magnetic flux of the rotating magnet. In accordance with this invention, an inductive pickup is disclosed having a core piece which acts as a conduction path for the magnetic field of the rotating magnet and further acts as a means for mounting the inductive pickup within the associated structure. Lead wires are imbedded within the bobbin and form protruding central conductors which act as posts to which each end of the coil wires are electrically and mechanically attached. The lead wires and core piece components are insert molded such that they are loaded into an injection molding die prior to the introduction of plastic material in a molten state which forms the bobbin component. The lead wire is sharply bent within the bobbin to insure firm engagement between the lead wire and bobbin. The tachometer generator according to this invention is simple and inexpensive to manufacture, and provides accurate installed positioning thereby enhancing performance.