Residual Field Indicator (Gauss Meter) – Full Description

A Residual Field Indicator, also known as a Gauss Meter, is a handheld measuring instrument used to check the amount of residual magnetism (remanence) present on a ferromagnetic component after Magnetic Particle Testing (MPI).

It ensures that the part has been demagnetized properly and meets acceptance standards.

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✔ Purpose

A Residual Field Indicator is used to:

• Measure remaining magnetic field after demagnetization

• Ensure residual field is within acceptable limits (usually < 3 Gauss)

• Identify areas where magnetism may cause:
  ✔ Interference with service performance
  ✔ Problems during welding, assembly, machining
  ✔ Attraction of metal debris in service

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✔ What It Measures

• Magnetic Flux Density in Gauss (G) or Tesla (T)

• Residual magnetism left in the part

• Polarity of magnetic field

• Leakage fields on steel surfaces

A Residual Field Indicator is typically single-axis, meaning it measures field strength in one direction at a time.

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✔ Construction & Components

1. Hall-Effect Probe

   • Sensitive to magnetic field

   • Usually transverse-type for surface measurements

   • Connected by shielded cable

2. Digital Display Unit

   • Provides numeric reading of Gauss/Tesla

   • Includes buttons for zeroing and unit selection

3. Zero Adjustment

   • Removes ambient magnetic influence before measurement

4. Power Source

   • Battery-operated for field use

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✔ Typical Specifications

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✔ How It Is Used in MPI (Step-by-Step)

1. Zero the Meter

   • Hold probe away from any magnetic object

   • Press “ZERO” or adjust manually

2. Place Probe on Component Surface

   • Keep probe flat and stable

   • Avoid vibration and movement

3. Read Gauss Value

   • Positive (+) or Negative (−) indicates polarity

   • Value indicates field strength

4. Compare With Acceptance Criteria

   • Commonly required residual field: < 3 Gauss
     (As per ASME, ASTM E1444, ISO 9934 guidelines)

5. If High Residual Magnetism Is Found

   • Repeat demagnetization

   • Recheck until acceptable

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✔ Applications

• Magnetic Particle Inspection (MPI)

• Demagnetization verification

• Checking magnetic leakage around welds

• Evaluating residual field in bearings, shafts, gears

• Ensuring safe assembly of precision parts

• Determining if magnetic field may cause service problems

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✔ Advantages

• High accuracy

• Portable and easy to use

• Fast response

• Essential for NDT (MPI) quality control

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✔ Limitations

• Affected by probe orientation

• Must be zeroed frequently

• Single-axis only (except advanced models)

• Requires calibration annually

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If you want, I can also provide:

📌 ALT image description of Residual Field Indicator
📌 Difference between Residual Field Indicator & Gauss Meter
📌 Calibration procedure
📌 Demagnetization acceptance criteria table

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