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Institut Dr. Friedrich Forster

Friedrich M Forster

A method and apparatus for electro-magnetically testing surface regions of elongated test objects for irregularities, such as flaws, and which is particularly suitable for testing test objects with non-circular or elliptical cross sections. Testing is performed by at least one coil, particularly an eddy current coil, through which a test object passes. The test coil has a coil plane passage of predetermined cross-section, and a modification of the passage cross-section of the test coil can be obtained by tilting the test coil. The test coil can optionally be rotated about an axis defined by the travel direction of the test object, and may also be moved in directions perpendicular to the travel direction. A disclosed apparatus for performing the method has several tiltable and rotatable and/or slidable test coils which are successfully arranged in the travel direction in the form of a coil group.

Method and apparatus for electro-magnetically testing elongated objects

A test head through which passes a test object has at least one test probe guided in a circular orbital path around the test object. The shape of the circular orbital path of the probe, when considered in the travel direction of the object, diverges in a predetermined manner from a circular shape. A rotor guides the probe on a circular path, and the rotational axis of the rotor can be tilted with respect to the travel direction of the test object. The rotor is driven by a driving unit positioned laterally to the travel direction on a base plate by a belt drive which runs in a transmission element carrying the test head and linking it with a drive unit.

Method and apparatus for testing elongated objects having a non-circular

A magnetic field differential probe has field sensors located at spaced intervals along a tensilely stressed diamagnetic wire free of mechanical support between the sensors.

Means for achieving parallelism of the magnetic axes of a differential

The elongated core of a magnetic field probe is constructed of a heat-resistant diamagnetic body with lengthwise openings into which are received closely fitting wires of a magnetizable material. The wires are secured to the body by a heat-resistant cement. An excitation winding wound onto the core extends substantially beyond the core wire ends and a receiver winding is slidably received on the core.

Harmonic magnetic field probe with novel core construction

Compensating magnets are located on the article being tested which are adjustable to provide a range of magnetic moments. In a first version, each compensating magnet consists of an annular permanent magnet received on a rod-like element positioned on the surface of the article, which magnet is adjustable with respect to the article surface. In a second version, the magnet is located at a fixed spacing with respect to the article surface and a shunt is adjustable to vary the compensating field.

Method and apparatus for compensation of interference magnetic fields

The force which is to act upon the tooth depends only on the field strength of an applied magnetic field, upon the length and number of the electrical conductors through which the magnetic field passes and upon the current flowing through the conductors. The rigid medium can alter its position relative to the examination head without current added to the area of constant field intensity altering the force. In this manner, it is also possible to achieve good examination results even without complicated, troublesome and expensive creation of a fixed point by means of a mouth insert. The head of the test subject is held still by means of a head or chin support. The transducer head can be alternatively retained in a support or even by hand. With the aid of an electronic function generator, any desired time function for the force acting on the tooth, regardless of whether a sinusoidal, rectangular, stepped or sawtooth increase in force is desired is produced.

Method and apparatus for examining human periodontal tissues

The magnetic gradient detector has two magnetic field sensors with their magnetic axes arranged parallel to an imaginary line. The sensor electrical outputs are connected with one another such that an electrical signal is created corresponding to the gradient of the magnetic fields present at the respective locations of the sensors. Each sensor has its core suspended on a wire under tension which maintains the parallelism constant. The wires are adjustable to establish initial parallelism or correct for subsequent misalignment that may occur.

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Reutlingen, Germany

Friedrich M Forster