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Specifying Scan Conditions for Hysteresis Tests

IP.com Disclosure Number: IPCOM000035053D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 39K

Publishing Venue

IBM

Related People

Bird, CL: AUTHOR [+2]

Abstract

Whenever measurements are to be made of the response of a material to a progressively applied force, there may be regions which are of greater interest than others. This calls for a flexible approach to measurement. This article discusses an approach to defining measurement conditions which divides the measurement into a sequence of segments. Each segment defines the region of interest and specifies the conditions for the measuring instrument necessary to reflect the degree of interest. The generation of hysteresis curves offers a typical example: the response depends on the existing state of the material, but the means of attaining that state may be of minimal interest.

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Specifying Scan Conditions for Hysteresis Tests

Whenever measurements are to be made of the response of a material to a progressively applied force, there may be regions which are of greater interest than others. This calls for a flexible approach to measurement. This article discusses an approach to defining measurement conditions which divides the measurement into a sequence of segments. Each segment defines the region of interest and specifies the conditions for the measuring instrument necessary to reflect the degree of interest. The generation of hysteresis curves offers a typical example: the response depends on the existing state of the material, but the means of attaining that state may be of minimal interest. Hysteresis curves may be obtained, for example, with: (a) the strain response of an elastic solid under applied mechanical stress [1], or (b) the magnetization response of a ferromagnetic solid in an applied magnetic field [2]. The latter case will be used to illustrate the segment concept, having been implemented for a Vibrating Sample Magnetometer (VSM) [3], operating under the control of an IBM PC-XT Personal Computer. Because of the hysteretic nature of ferromagnets, the values depend on the sample history. Conventionally, to overcome this, a reproducible hysteresis loop (Fig. 1) is measured between large positive and negative fields.

These hysteresis conditions would typically be specified in terms of the maximum field, which is likely to be fixed as the same in + and - senses, and some determinant(s) of the scan rate. The latter would apply throughout the scan. As a result, points are collected at equal intervals and in the same manner for the entire scan. This rate is a compromise between measurement time, sensitivity and accuracy. Following the segment approach, each test segment defines a unidirectional component of the overall scan and specifies the conditions to be applied for that one component. A sequence of segments forms the full scan definition, with individual segments differing from each other to whatever extent is required by the user.

In Fig. 2, the scan producing a typical hysteresis loop is notionally split into three sections, each of which can be defined as a single segment. Si indicates the start of segment i and Di its destination. While the order of the segments is fixed, the conditions applied may be varied considerably from one to the next.

The following information is required to describe a single segment:
1. Destination Field...