What Is Magnetic Field Mapping?
Magnetic field mapping is the process of measuring magnetic flux density at multiple spatial positions to characterize how it varies along a defined path or across an area.
Unlike single-point Gauss measurements, mapping connects measured values with their corresponding positions and therefore describes the spatial distribution of magnetic flux density.
The measurement points may be acquired sequentially by moving Hall probes relative to permanent magnets or magnetic assemblies, or simultaneously using arrays of Hall sensors.
Linear scans measure how magnetic flux density changes along a defined direction, while circumferential scans around multipole ring magnets and magnetic rotor assemblies can record the distribution over a complete 360º rotation.
The resulting data do not always appear as conventional field maps. Circumferential measurements are commonly displayed as magnetic flux density waveforms, while measurements collected across many positions over an area can be presented as contour plots, color maps, or other two-dimensional distributions. Magnetic field cameras, such as Magcam systems, use dense Hall sensor arrays to acquire magnetic flux density at many positions simultaneously rather than scanning each location individually.
In this sense, magnetic field mapping covers both scanning-based measurements and direct field mapping with sensor arrays. The common purpose is to describe how magnetic flux density varies spatially instead of reducing magnetic performance to a single Gauss or Tesla value.
Why a Single Gauss Value Is Not Enough?
Single-point Gauss measurements are useful when magnetic flux density at a specific location is the main inspection requirement. Surface measurements at a defined position, for example, can provide a convenient reference for comparing magnets of the same geometry, magnetization direction, and measurement setup.
However, magnetic flux density is highly dependent on position. Measurements taken only a few millimeters apart may differ significantly, particularly near magnet edges, pole transitions, and air gaps. A single value therefore describes only the local magnetic flux density at the measurement point rather than the overall magnetic distribution.
This limitation becomes more important for multipole magnets and complex magnetic assemblies. Two components may show similar maximum Gauss values while having different pole distributions, field uniformity, or symmetry across their working regions. Maximum flux density alone cannot reveal where magnetic peaks occur, how rapidly the field changes between positions, or whether the distribution follows the intended design.
Magnetic field mapping addresses this limitation by replacing an isolated measurement with a series of spatially related measurements. The resulting waveform or field map preserves information about how magnetic flux density changes across the measured region, allowing magnetic performance to be evaluated as a distribution rather than as a single value.
From Single-Point Measurements to Magnetic Flux Density Waveforms
When magnetic flux density is measured repeatedly along a defined path, individual Gauss values can be combined into a continuous spatial profile. Each measurement corresponds to a position along the scanning path, so the resulting waveform shows how magnetic flux density changes along that path rather than at only one location.
For linear scans, Hall probes move along a straight path while the measurement distance and probe orientation remain controlled. The result can be expressed as magnetic flux density versus position, allowing variations across magnet surfaces, air gaps, or working regions to be observed directly.
For multipole ring magnets, magnetic rotors, and other rotational magnetic components, circumferential scanning is commonly used. Hall probes remain at a defined radial or axial distance while the magnetic components rotate through 360º. The measured magnetic flux density is then plotted against angular position, producing a periodic waveform that reflects the magnetic pole distribution around the circumference.
These waveforms can already be considered a simple form of magnetic field mapping. Instead of reducing multipole magnetic performance to a maximum Gauss value, they preserve the spatial relationship between successive poles and provide the basis for more detailed waveform analysis.
What Can Be Learned from Magnetic Flux Density Waveforms?
Magnetic flux density waveforms provide more information than peak Gauss values alone. Because each point on the waveform corresponds to a position or angle along the scanning path, the waveform can be used to evaluate the strength, position, width, and consistency of individual magnetic poles.
Peak Values and Pole-to-Pole Consistency
Peak values show the maximum positive or negative magnetic flux density associated with individual poles. Rather than considering only the highest value measured over a complete scan, the peaks can be compared from pole to pole.
Peak deviation indicates how consistently the magnetic poles reach their expected flux density. Differences between successive peaks may result from variations in magnetization, magnetic material, geometry, or assembly conditions.
Pole Angle, Pole Angle Deviation, and Duty Cycle
Pole angle describes the angular width associated with individual magnetic poles, while pole angle deviation shows how consistently these widths are distributed around the circumference. Comparing pole angles helps reveal uneven magnetic pole distribution even when peak values remain similar.
Duty cycle describes the relative angular widths of positive and negative regions within each magnetic cycle. A balanced waveform may approach a 50/50 distribution between opposite polarities, although the exact value depends on how the pole boundaries are defined in the measurement system.
Waveform Area and Magnetic Balance
Waveform area considers the magnetic flux density over an angular or linear interval rather than only its peak value. Poles with similar peak flux densities can still have different waveform areas because of differences in pole width or distribution shape.
Comparing waveform areas between individual poles, or between positive and negative regions, provides another way to evaluate the balance and consistency of the magnetic distribution.
However, waveform area should not automatically be interpreted as magnetic flux. Integrating magnetic flux density with respect to angle or linear position gives an integral of the measured waveform, while magnetic flux requires magnetic flux density to be integrated over a physical area.
From 1D Scans to 2D Magnetic Field Maps
1D scans describe how magnetic flux density varies along selected paths. The paths may be linear or circumferential, with the resulting data expressed against linear position or angular position. These measurements can reveal local peaks, transitions, and variations along the scanned paths, but information outside those paths is not captured.
Two-dimensional magnetic field maps extend this approach by collecting measurements across defined areas rather than along individual paths. These maps can be generated by repeating 1D scans at different positions or by using magnetic field cameras with two-dimensional arrays of Hall sensors.
The measured values can then be displayed as color maps, contour plots, or surface plots, making spatial variations across the mapped areas easier to identify.
Surface plots may appear three-dimensional because magnetic flux density is displayed as height above the measurement plane. However, the underlying measurements can still represent two-dimensional spatial distributions. Similarly, magnetic field cameras capable of measuring multiple field components should not automatically be confused with volumetric 3D mapping, which requires measurements at different positions in all three spatial directions.
The additional spatial information becomes important when magnetic flux density varies in more than one direction. 1D profiles may show that the expected flux density is achieved along selected paths while missing asymmetry, localized weak regions, edge effects, or displacement of magnetic patterns elsewhere. 2D maps preserve this information and can also be used to extract selected 1D profiles for further analysis.
Measurement conditions remain important when comparing field maps. Measurement distance, mapped area, spatial resolution, and the relative positioning between sensors and magnetic components should remain consistent, since changes in measurement geometry can affect the observed magnetic flux density distribution.
From 1D Scans to 2D Magnetic Field Maps
Finite element analysis can predict magnetic flux density distributions before magnets or magnetic assemblies are manufactured. Simulated maps help evaluate expected field patterns, working regions, air-gap effects, and changes caused by geometry or magnetic circuit design.
Measured field maps provide the corresponding distributions from physical components. Comparing measured and simulated results can reveal differences caused by material variation, incomplete or uneven magnetization, assembly tolerances, positioning errors, or deviations in actual air gaps and component geometry.
For meaningful comparison, simulations and measurements should use equivalent reference positions, measurement distances, scanning areas, and magnetic flux density components. Differences in these conditions can produce apparent discrepancies even when the magnetic systems behave as intended.
Used together, FEA simulation and magnetic field mapping provide complementary information: simulations predict how magnetic systems should behave, while measurements show how manufactured components actually perform. This comparison is particularly useful when magnetic performance depends on spatial distribution rather than on individual Gauss values alone.
