Spinner Magnetometer

Overview: The JR‑6A is a state‑of‑the‑art spinner magnetometer for measuring remanent magnetization in geological and archaeological research. Its combination of automation, sensitivity, and robustness makes it one of the premier instruments in rock magnetism laboratories worldwide. It is the automated version (“A” stands for automatic manipulator) of the JR‑6, capable of rotating and orienting samples automatically for full vector measurements. 

The instrument can measure discrete samples but has the benefit of measuring just the remanent magnetization and not the induced magnetization as the SRM potentially does. 

Working Principle: The rock specimen (cylinder or cube) is rotated at a constant speed inside Helmholtz coils. The induced AC voltage corresponds to the magnitude and direction of the specimen's remanent magnetization. A microprocessor-based system controls rotation, digital filtering, and data transfer to a computer.

Key specifications

• Sensitivity (high speed): ~2 × 10⁻⁶ A/m
• Measuring range: Up to 12,500 A/m
• Rotation speeds: High: 87.7 rps, Low: 16.7 rps
• Specimen size (cylinder): Ø 25.4 mm × 22 mm
• Specimen size (cube): 20 × 20 × 20 mm
• Power supply: 100–240 V, 50/60 Hz

Applications

- Palaeomagnetism: studying ancient geomagnetic fields in rocks.

- Archaeomagnetism: dating archaeological materials via remanent magnetization.

- Rock magnetism and mineralogy: determining magnetic properties and mineral content.