Browse Prior Art Database

Gradiometer Hall Probe

IP.com Disclosure Number: IPCOM000112287D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Chi, CC: AUTHOR [+2]

Abstract

Hall probes are common magnetic field sensors. They are easy to use and inexpensive in comparison to other sensors such as flux gate and SQUID magnetometer. However, for measuring weak fields generated by a nearby source in the presence of a large uniform background, it is often necessary to use a gradiometer instead of a magnetometer to achieve sufficient signal to noise ratio. Up to now, there have been many designs of SQUID gradiometers but, no Hall gradiometers. With this invention the utility of the Hall probe will be greatly enhanced. Since Hall gradiometers can operate in higher ambient magnetic fields and at higher ambient temperatures than SQUID gradiometers, new applications are possible.

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Gradiometer Hall Probe

      Hall probes are common magnetic field sensors.  They are easy
to use and inexpensive in comparison to other sensors such as flux
gate and SQUID magnetometer.  However, for measuring weak fields
generated by a nearby source in the presence of a large uniform
background, it is often necessary to use a gradiometer instead of a
magnetometer to achieve sufficient signal to noise ratio.  Up to now,
there have been many designs of SQUID gradiometers but, no Hall
gradiometers.  With this invention the utility of the Hall probe will
be greatly enhanced.  Since Hall gradiometers can operate in higher
ambient magnetic fields and at higher ambient temperatures than SQUID
gradiometers, new applications are possible.  These applications
include:  measurement of biological magnetic sources or responses
such as the human heart and the arteries for diagnostic purposes,
examination of defects in IC packaging parts, circuits and wirings,
and detection of buried magnetic objects.

      Disclosed is a new scheme to measure magnetic field gradient
using Hall effect, shown in Fig. 1.  The sensor is a closed loop
(Hall loop) made of materials with large Hall coefficient such as
InSb, GaAs, Si, or Ge.  An ac circulation current is induced through
an externally generated ac magnetic flux in the loop.  The voltage
difference between the two voltage leads (A and B), which are placed
on the opposite ends of the loop in the desired direction, is
proportional to the field...