Why Two 'X Gauss' Magnets Can Perform Completely Differently

A Gauss rating on a spec sheet only means something if you know exactly how it was measured - at what distance, at what point on the magnet, and under what conditions. Two separators can both be sold as "4,000 Gauss" and perform completely differently in your process, because that single number can be measured at least three different ways, and only one of them tells you what will actually happen to the material passing through your line.

The Same Number Can Mean Three Different Measurements

Pole-Face Gauss vs. Working-Gap Gauss

Magnetic field strength falls off sharply with distance from the magnet's surface. A reading taken with a Hall probe held directly against the pole face can be several times higher than the field at 10mm, 25mm or 50mm away, which is where your material actually passes on a conveyor, in a chute, or through a pipeline. A separator quoted at "4,000 Gauss" measured at the pole face might deliver a fraction of that at the working gap your process actually uses. If a quote doesn't state the distance the rating was measured at, assume it's the pole face - the biggest, least useful number available.

Peak Gauss vs. Average Gauss Across the Working Area

A magnet's field isn't uniform across its whole face. There's almost always one hotspot! An edge, a corner, a specific point in the geometry, where the field peaks higher than everywhere else. A rating taken at that single peak point describes one square centimeter of the magnet, not the average field your material experiences as it moves across the full width of the pole face. Separation performance depends on the average field across the effective capture area, not the single highest point on the unit.

Fresh-Off-the-Line Gauss vs. Sustained Gauss in Service

Rare-earth (NdFeB) magnets lose field strength as temperature rises - this is reversible up to a point, but the field you measure on a magnet fresh out of the box at room temperature is not necessarily the field it delivers after hours of operation at your process temperature. A rating with no stated test temperature or duration is, by default, the best-case number, measured once, under ideal conditions, and never checked again.

What This Looks Like in Practice

We've tested separators on the market rated at 4,000 Gauss that measured well under 1,500 Gauss once checked at the actual working gap, with a calibrated meter. That's not a rounding error, that's the difference between a unit that reliably captures fine ferrous contamination and one that lets it straight through while the nameplate says otherwise. The buyer never finds out until contamination shows up downstream, in a customer complaint, a failed batch, or damage to equipment further down the line.

Four Questions to Ask Before You Buy Any Magnetic Separator

1. At what distance was this Gauss rating measured?

   Pole-face and working-gap numbers can differ several times over. Ask for the rating at your actual process gap, not the magnet's surface.

2. Is this a peak reading or an average across the pole face?

   A single hotspot reading tells you almost nothing about real-world capture performance.

3. Was it tested fresh, or at operating temperature after time in service?

   Ask what temperature and duration the test was run at — a number with no conditions stated is the best case, not the expected case.

4. Can you show me a calibrated, third-party test certificate?

   A number on a spec sheet is a claim. A certificate from a government-approved third-party lab, with a specific date, instrument and reading, is evidence.

How PML Tests and Rates Every Unit

Every safety and field-strength rating PML publishes is verified on our own in-house testing equipment - including Koerzimat and BH Loop Plotter instruments for precision magnetic measurement - and backed by test certificates issued by government-approved third-party labs, not just an internal spec sheet. That's the difference between a rating and a rating you can check. If you want the full story on how we test and what our verification actually covers, see why PML costs more than the cheapest quote you'll find, and what that premium is actually protecting you from.

Frequently Asked Questions

Not sure whether the separator you're being quoted will actually hit its stated rating in your process? Talk to our engineering team or message us on WhatsApp - we're glad to help you check the numbers, even on a quote from somewhere else.