| 摘要 |
The magnetic-field test set contains a magnetic-field sensor having four sensor elements which are connected as a Wheatstone bridge, are supplied from a DC source (7) and have a layer of magnetoresistant material through which the DC current flows on current tracks which are aligned at right angles to one another on in each case two series-connected sensor elements and are aligned parallel to one another on sensor elements which are diagonally opposite one another. In this case, the sensor elements (1-4) have magnetic preferred directions, which point in the same direction (5). In order that the magnetic-field test set supplies error-free magnetic-field measurements, that is to say which are independent of manufacturing tolerances and temperature drift of the sensor elements, a magnetising coil (9) is arranged in the vicinity of the sensor elements (1-4), which magnetising coil (9) is supplied from a current-pulse generator (10) with short, alternately positive and negative current pulses which produce a magnetic alternating field in the magnetising coil (9), which magnetic alternating field reverses the magnetisation of the magnetoresistive material in synchronism with the current pulses, as a result of which an AC voltage is produced on the null branch of the sensor bridge, the amplitude of which AC voltage corresponds to the intensity of the magnetic field which is to be measured and can be measured by means of an evaluation circuit (8) which is connected there. <IMAGE>
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