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Device for Measuring the Homogeneity of Magnetic Dispersions

IP.com Disclosure Number: IPCOM000050711D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

DePalma, V: AUTHOR [+3]

Abstract

A magnetoresistive (MR) device is employed to measure the homogeneity of magnetic dispersions. Previous devices use a magnetic inductive transducer for measurement of homogeneity of magnetic dispersions. Such devices are highly dependent upon the relative velocity of the transducer and the magnetic fluid since signal is proportional to the rate of change of flux with time. As a consequence, such devices have several disadvantages: 1. Low signal amplitude. 2. Inductive devices require high relative velocity between the transducer and the fluid, thus rendering the device (pump, constant pressure device, etc.) more complex than necessary.

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Device for Measuring the Homogeneity of Magnetic Dispersions

A magnetoresistive (MR) device is employed to measure the homogeneity of magnetic dispersions. Previous devices use a magnetic inductive transducer for measurement of homogeneity of magnetic dispersions. Such devices are highly dependent upon the relative velocity of the transducer and the magnetic fluid since signal is proportional to the rate of change of flux with time. As a consequence, such devices have several disadvantages: 1. Low signal amplitude. 2. Inductive devices require high relative velocity between the transducer and the fluid, thus rendering the device (pump, constant pressure device, etc.) more complex than necessary.

Alternatively, a magnetoresistive device used for this application possesses two features offering distinct advantages: 1. Signal is flux sensitive only and therefore velocity independent. 2. A higher signal to noise ratio due primarily to higher amplitude capability for the same sensed magnetic field 4x to

10x greater sensitivity.

Alternate forms of the MR transducer that can be used for this application are: 1. An unbiased shielded stripe. 2. A biased stripe, e.g., a. Shunt bias

b. Anti-ferromagnetic exchange coupled bias

c. Soft film bias

d. Barber-pole bias

e. Two-turn shielded bias with zero external fringe field.

Since magnetic particles are attracted towards sources of magnetic fields, it is important to minimize the external field and gradient at the MR device. St...