THM1176/TFM1186 Use
r’s Manual
v 2.0 r 1.0
– 02/20
Copyright © 2020 Metrolab Technology SA
www.metrolab.com
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REFERENCE
7-
THM1176-MF/HF/HFC Sensor Details
This chapter is adapted from an article by Philip Keller of Metrolab in the
June/July 2008 issue of Magnetics Business & Technology
http://www.MagneticsMagazine.com
To measure the total field, we need three orthogonally
oriented Hall sensors. Typically, three individual sensors
are glued into a cube, roughly five to ten millimeters on a
side. But now there is another way: a single IC containing
one conventional planar Hall element and two sets of
“vertical” Hall elements.
The vertical elements can be thought of as plates of N-type silicon inserted
vertically into a P-type substrate. If a current is injected into the center terminal
and extracted from the two end terminals, the
currents in the two halves of the plate flow in
opposite directions, resulting in a Hall voltage on
the remaining terminals.
A team at the EPFL in Switzerland, led by Dr.
Popovic, applied this technique to design a 3-axis sensor on an IC, called the
MAG3D. The array of Hall elements measures 150 x 150 x 10 µm
3
– a million-fold
reduction in active volume compared to a conventional approach! This allows
precise position determination as well as consistent measurements of all three
components even in highly inhomogeneous fields.
But MAG3D contains much more than the Hall elements. To build a Hall
magnetometer, we need to supply a current and measure a voltage. By increasing
the current and/or amplifying the voltage, one can increase the sensitivity. All this