AlNiCo magnets are known for their excellent temperature stability, high residual induction, and long service life. Whether you are manufacturing motors, sensors, or measuring instruments, understanding their magnetic performance is key.
When it comes to testing AlNiCo magnets, two common tools are:
- Gaussmeter (Tesla meter) – Measures surface magnetic field strength.
- Demagnetization curve (B-H curve) testing – Measures the complete magnetic property data of a material.
While both methods are useful, they serve different purposes.
1. What a Gaussmeter Does
A Gaussmeter measures surface flux density at a specific point, usually in units of Gauss (G) or Tesla (T). It is quick and easy to use, making it ideal for:
- Incoming quality checks – Ensuring magnets are magnetized correctly.
- Field service – Checking whether a magnet has weakened over time.
- Sorting – Separating stronger and weaker magnets in production.
Limitations for AlNiCo:
- Not a full picture – A single surface field reading doesn’t tell you coercivity, remanence, or the full energy product.
- Shape and size effect – Irregular shapes cause uneven fields, leading to variation in readings.
- Measurement direction – AlNiCo’s anisotropy means the reading changes if the probe is not aligned with the magnetization axis.
2. What a Demagnetization Curve Does
A demagnetization curve (B-H curve) test applies a controlled reverse magnetic field to the magnet and measures how it loses and regains magnetization.
It provides full magnetic characteristics, such as:
- Br (remanence) – Magnet’s residual flux after full magnetization.
- Hc (coercivity) – Resistance to demagnetization.
- (BH)max – Maximum energy product.
- Full hysteresis loop – Showing magnetization, demagnetization, and re-magnetization behavior.
Advantages for AlNiCo:
- Complete data – Useful for research, design, and quality control.
- Independent of magnet shape – Unlike a Gaussmeter, it’s not affected by surface geometry as much.
- Identifying material grade – The curve can confirm if a magnet meets the specification of AlNiCo 5, AlNiCo 8, etc.
3. Which Should You Use?
- For quick checks or field measurements: Use a Gaussmeter.
- For full performance evaluation, grade verification, or R&D: Use a demagnetization curve test.
Conclusion
Gaussmeters are fast and convenient, but their readings can be influenced by shape, alignment, and surface effects — especially with anisotropic materials like AlNiCo. A demagnetization curve test, while slower and requiring specialized equipment, provides a complete and reliable assessment of the magnet’s properties, making it essential for critical design work or quality control.
In short:
- Gaussmeter = Quick surface strength check.
- Demagnetization curve = Complete magnetic profile.
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