B8.1 - Accurate Measurement Setup for Strongly Inhomogeneous Magnetic Fields

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
B8 - Magnetic Sensors
H. Husstedt, M. Kaltenbacher - Alps-Adriatic University, Klagenfurt (Austria), U. Ausserlechner - Infineon Technologies Austria AG, Villach (Austria)
343 - 348


The testing of magnetic sensors for automotive applications includes not only electrical but also magnetic tests. For each sensor, dedicated test equipment generates magnetic reference fields which vary from homogeneous, to differential and rotating fields. Some of these fields are strongly inhomogeneous with a gradient up to 1%/10μm. For the analysis of these test equipments, the spatial dependency of the reference fields has to be measured around the position where the sample is placed during the test.
State of the art systems, that can measure the spatial dependency of magnetic fields, mount a magnetic sensor in a coordinate measuring machine (CMM) which consists of several moving axis. In the measurement system, a magnetic sensor is positioned at several points where the magnetic field is measured. Such a scan provides roughly the field vector w.r.t. the geometry of the field source. However, if the fields are strongly inhomogeneous, small assembly tolerances of the magnetic sensor and the field source lead to crucial measurement errors.
Our approach is a measurement system that consists of a CMM with magnetic sensors and an optical sensor for geometrical measurements. First, the optical sensor measures the geometry of the field source so that its exact position and alignment in the setup is known. Now, the magnetic sensor can scan the magnetic field at points relative to the field source. Finally, the measured field vectors can be transformed to the reference frame of the field source so that assembly tolerances have no influence any more. Nevertheless, the magnetic field can only be measured w.r.t. the coordinate system of the field source, if the alignment and position of the magnetic sensor is exactly known. Therefore, a calibration of these parameters is necessary.
To conclude, our approach allows to measure magnetic fields w.r.t. the geometry of the field source with a spatial accuracy of 10μm and an alignment of the magnetic sensor better than 0.1°. Thus, strongly inhomogeneous magnetic fields, such as reference fields testing magnetic sensors, can be measured accurately.