Different readings on the same magnet should first trigger a review of the measurement: the sensing location, direction and effective distance must be comparable. Two numbers alone do not establish the material grade, magnetization condition or a batch defect. Record the conditions before interpreting the difference.
Separate a center value from an edge or scanning peak
The field changes with location. A center reading, an edge reading and a peak found by scanning should not all be labeled simply “surface field.” Define where the result is taken and whether it is a fixed-point or scanning result.
If one test uses the center and another searches for the maximum, different results need not imply a changed sample. Repeatable positioning matters particularly where the local field varies strongly. A fixture or a clear location photograph helps define the test.
Locate the active sensing element
Probe-body contact does not put the active sensor directly on the pole face. A Hall probe has an offset between its housing or tip and its active region, and a finite sensing area. Use the instrument and probe specifications when defining distance.
Principle illustration only: the indicated distance is between the active sensing point and pole face. It is not the geometry of a particular probe. Confirm orientation, active area and offset from its documentation.
Review direction, range and zero
A single-axis probe senses the corresponding field component; changing its angle can change the reading. Axial and transverse probes use different geometries, and polarity signs depend on orientation and convention. Record the direction and use a fixture where needed.
Check range, units, zeroing and instrument condition according to the manual. Display resolution is not the accuracy of the complete measurement. More displayed digits do not resolve damaged probes, unsuitable ranges or inconsistent positioning.
| Record | What to include |
|---|---|
| Sample | ID, revision, dimensions and pole face |
| Instrument | Probe/meter model, range, units and relevant calibration information |
| Location | Sensing point, orientation and positioning method |
| Distance | Active-element spacing or an agreed repeatable arrangement |
| Environment | Temperature, fixture and nearby steel or magnets |
| Result | Value, polarity sign, repeat observations and anomalies |
Separate assembly effects from model assumptions
Nearby ferromagnetic parts, other magnets and the assembly can alter the field environment. A loose magnet and a magnet in a metal assembly are not automatically the same test condition. Describe the fixture and surrounding structure.
The website estimator returns a value defined by an ideal model. A real probe has finite area and offset. Align geometry, material input, position and spacing before comparing the two; an ideal axial point value is not an arbitrary scanning-peak guarantee.
Repeat the conditions before diagnosing the difference
Check units and location first, then orientation, effective spacing and nearby structures. Discuss material or magnetization factors after these are aligned. One surface reading generally cannot establish a complete material-grade conclusion.
Start with the sensing-position photographs, instrument/probe models, distance definition and both sets of records. Comparable conditions turn a disagreement between numbers into a reproducible question and help define later sample and batch checks.