Surface field estimate
Estimate the theoretical pole-centre field of a disc, cylinder or block using dimensions, remanence and distance.
Diagram is not to scale. The point lies on the centre axis, not at a scanned edge.
— mT
For parameter comparison and initial selection; not a scan peak, pull force or guaranteed finished-part value.
How to approximate a measurement
Contact between the probe casing and magnet does not mean zero sensing distance. Use the active sensor offset and confirm position, temperature and magnetization.
When is a separate assessment needed?
This uniform-magnetization model covers a single ideal solid magnet. Rings, custom shapes, multipoles, assemblies or nearby steel need application-specific assessment. For bonded magnets, use actual remanence rather than sintered presets.
Model, assumptions & references
Uses analytical centre-axis fields for cylinders and rectangular prisms in free space with uniform magnetization. Recoil permeability differing from 1 and magnetization changes due to self-demagnetization are neglected. Reference remanence is for room temperature; no temperature correction is applied. Coatings, chamfers and measurement offsets are not separately modelled. Dimension bounds of 0.001–10000 mm are tool limits, not supply specifications.
Cylinder: B = Br/2 × [(z+h)/√(R²+(z+h)²) − z/√(R²+z²)]
Block: B = Br/π × [atan2(ab, z√(z²+a²+b²)) − atan2(ab, (z+h)√((z+h)²+a²+b²))]
R is radius; a and b are half the pole-face dimensions; h is magnetization thickness; z is distance from the pole face. 1 T = 10000 G = 1000 mT. Display precision is not measurement accuracy.
Model references: Surface fields and geometry · Probes and measurements · Typical remanence data