GJB 937A-2021

Method for measuring magnetic permeability of weakly magnetic materials (English Version)

Standard No.

GJB 937A-2021

Language

Chinese, Available in English version

Release Date

2021

Published By

Military Standard of the People's Republic of China-General Armament Department

Latest

GJB 937A-2021

Introduction

Analysis of Standard Technology Evolution

GJB 937A-2021 replaces the 1990 version of the standard. The main technical upgrades include:

Technical Dimensions	GJB 937-1990	GJB 937A-2021
Measurement Method	Compensated Air Flux Impact Method	Solenoid Method/Magnetic Moment Method/VSM Method/Magnetic Balance Method
Measurement Range	1.003-2.0	Extended to 1.001-5.0
Appendix content	None	3 new appendices (including self-demagnetization correction)

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Comparison of core measurement methods

1. Solenoid method (preferred method)

Technical parameters:

• Measurement range: 1.003-2.0
• Magnetic field strength: 5-100kA/m
• Aspect ratio requirement: ≥10:1
• Uncertainty: ≤0.5%

Test device must meet the following requirements:

1. Solenoid aspect ratio ≥10:1
2. Detection coil winding error ≤ 0.2%
3. Flux integrator accuracy ≥ 0.5%

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2. Vibrating Sample Magnetometer Method (VSM)

Parameters	Requirements
Sample size	Diameter/thickness ratio ≥ 5
Magnetic field intensity	±400kA/m
Data acquisition	≥20 sets of forward and reverse data

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Implementation suggestions

Laboratory Configuration Plan

1. Basic Configuration:Solenoid Method Apparatus (Aspect Ratio 15:1) + Flux Integrator (Class 0.2)
2. Extended Configuration:Add VSM System (Sensitivity 10^-6Am²)
3. Calibration Requirements:Coil Constant Calibration Must Be Traceable to the National Magnetic Field Intensity Standard

Key Points for Self-Demagnetization Correction

When the aspect ratio of the specimen is <10:1, correction must be made according to Appendix C:

Correction Formula: ΔJ = (N_fA_w/A_s)J

Where N_f is the flux demagnetization factor (see IEC 60404-15)

GJB 937A-2021 history

• 2021 GJB 937A-2021 Method for measuring magnetic permeability of weakly magnetic materials
• 1990 GJB 937-1990 Method for measuring magnetic permeability of weakly magnetic materials