Siemens Aktiengesellschaft

Gabriel M Daalmans

Roland Finkler

Klaus Weinzierl

Klaus Ludwig

Franz Bauer

Hans-Peter Lohmann

Erich Becker

Viktor Wesselak

Martin Steck

Ludwig B&auml;r

Ruediger Doell

An apparatus for detection of the gradient of a magnetic field includes at least four antenna elements () composed of a ferromagnetic material, which are arranged in pairs, and a bridge circuit having at least four resistance elements (), which are associated with the antenna elements () or antenna element pairs. Each antenna element pair has at least one associated resistance element () whose resistance value is dependent on the field strength and on the direction of the magnetic field, and which resistance element () is arranged in a field area () which extends between the two antenna elements () of the antenna element pair. The invention also relates to a method for production of an apparatus which is intended for detection of the gradient of a magnetic field.

Apparatus for detection of the gradient of a magnetic field, and a method for production of the apparatus

Disclosed is a device for detecting defects which are deep in electrically conductive materials in a non-destructive manner, comprising an excitation device provided with induction coils which are used to produce low frequency eddy currents in the material, and a receiving device for the magnetic field of the eddy currents, the magnetic field being modified by the defects, and the receiving device comprising a gradiometer magnetic field sensors with an integrated bridge circuit.

Device for detecting defects in electrically conductive materials in a nondestructive manner

In a motion detector according to the Ferraris principle, an excitation element applies an inhomogeneous time-dependent alternating magnetic field to an induction element. A motion of the induction element induces in the induction element an eddy current with a temporal characteristic that depends both on the velocity and the acceleration. A sensor element measures the temporal characteristic of the eddy current and supplies the temporal characteristic to a signal processing circuit which determines at least one useful signal that is proportional to the velocity and acceleration, respectively.

Motion detector according to the Ferraris principle

In order to compensate for a drop in sensitivity at high rotational speeds, an acceleration sensor having an inductive measuring head (T) which cooperates with a moving Ferraris disk (F) essentially over a main magnetic field and which supplies an acceleration-dependent variable (Vdet; V&#x3b1;) is expanded by an additional DC magnetic field excitation circuit (, I, R) with a means for driving the latter with the effect that the additional DC magnetic field acts in a compensating fashion on an eddy-current DC field, starting from a relatively high rotational speed (&#x3c9;) of the Ferraris disk (F). This can be performed by amplifying the main magnetic field or by reducing the eddy-current DC field. A control signal (V&#x3c9;), dependent on rotational speed, which both can be generated outside the sensor via a characteristic curve, and can be derived in the form of a control loop from the sensor signal (V&#x3b1;), serves as a drive.

Circuit arrangement for evaluating an acceleration sensor using the Ferraris principle

A device for measuring a motion of a moving electrically conducting body is disclosed. A magnetic field generated by, for example, electromagnets or permanent magnets, penetrates at least a partial area of the moving body. Two or more measuring devices are arranged outside the magnetic field to measure a measurement magnetic field that is induced by electrical currents in the moving body. The measuring devices are arranged essentially symmetrically with respect to the magnetic field generating means or the moving body. The measurement magnetic field represents at least one motion variable of the moving body. The measuring device is thereby no longer subjected to the temperature-dependent variations of the exciting field.

Device for measuring the motion of a conducting body through magnetic induction

A method and measuring device for the in situ detection of the &ggr;-&agr; phase transformation of strip steel. The detection takes place on the basis of the eddy currents of the nonmagnetic phase, which are caused from the workpiece when an electromagnetic excitation field is applied, and on the basis of response fields which are generated by the magnetic phase which may be present. At least one electromagnetic excitation field which acts on the workpiece is generated by means of at least one excitation coil, and a response field which results from the application of the excitation field is measured by means of at least one detector measurement coil. The resulting measurement signal, which is dependent on the distance between the measuring device and the workpiece, is used to detect the degree of transformation.

Method and device for the in situ detection of the degree of conversion of a non-magnetic phase in a ferromagnetic phase of a metallic work piece

A motion parameter of an at least partially conducting moving body is measured with a measuring device having at least one coil with a coil axis tangential to the motion direction of the moving body. A primary magnetic field induces electrical currents in the moving body that generate a motion-dependent measuring magnetic field which is measured by the measuring device. The tangential coil(s) has/have a greater distance from the moving body than the primary magnets.

Device for eddy current measurement of a motion of a conducting body in a magnetic field

A scanning head for eddy-current testing includes a probe coil configuration disposed on a film on a film base. The film base is matched to a shape of an object to be tested. This allows quick, low-interference eddy-current testing. A method for producing a scanning head for an eddy-current test and an eddy-current test method are also provided.

Scanning head for eddy-current testing, method for processing a scanning head for an eddy-current test method

The SQUID magnetometer for a device for the single-channel or multi-channel measurement of very weak magnetic fields caused by at least one field source to be detected contains at least two super-conducting gradiometer loops which, with two Josephson tunnel elements form a d-c SQUID. This magnetometer should have high sensitivity with good interference suppression. At least one detection loop and at least one compensation loop are located as the gradiometer loops as well as the Josephson tunnel elements together with superconducting connecting conductors between these parts one behind the other on a three-dimensional surface of a carrier and the mutual distance between the detection loop and the compensation loop is chosen sufficiently large that the magnetic flux, also picked up by the compensation loop of the field source to be detected, amounts to at most 20% of the magnetic flux picked up by the detection loop.

SQUID-magnetometer for measuring weak magnetic fields with gradiometer

A SQUID magnetometer is disclosed which can be fabricated by thin-film technology and used for apparatus for measuring weak magnetic fields. It contains a d-c SQUID with a SQUID loop surrounding the effective area of a coupling hole as well as a superconducting flux transformer with a gradiometer coil and a coupling coil surrounding the coupling hole thereby to achieve an effective inductive coupling of a measuring signal into the SQUID. To this end, the invention provides a separate superconducting surface (3a) with the coupling hole (4), to which the coupling coil (8) and or the SQUID loop (12) is/are assigned. The coupling coil (8) surrounds the SQUID loop (12) while maintaining a sufficient distance (e) for d-c decoupling.

Thin film SQUID magnetometer for a device for measuring weak magnetic

For manufacturing a gradiometer having a three-dimensional structure for a device for measuring magnetic fields with field intensities down to below 10.sup.-10 T, the superconducting gradiometer coils are arranged on a support body and are coupled by means of superconducting connecting lines and a coupling coil to a superconducting quantum interference element (SQUID) which is located on a substrate body of its own. These gradiometers should be capable of being linked to the respectively assigned SQUID in a simple manner. For this purpose, the gradiometer coils and at least the associated connecting lines are applied onto a common three-dimensional support body in at least one coating operation which is either preceded by a lithographic process for the fixation of the position of the corresponding conductor runs, or is followed by an etching process.

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Erlangen, Germany

Gabriel M Daalmans