We measured our lab's Magnetic Pulser MP7 test unit at both settings. Here is what a full report shows beyond one peak Gauss figure.

A PEMF mat and a grounding mat can look nearly identical in photos. One is built around coils that make a changing magnetic field, and that field is what a lab can measure.

A few readings above the center show how quickly a field fades with height. A real five-height test shows what they leave out: how far the field spreads sideways, and whether it spreads evenly.

Whoever draws a PEMF mat's field map decides how to fill the space between scan lines and where the color scale tops out. Here's how each choice changes the same data.

Buyer guides now say a sealed mat can't be checked. It can: the field sits in the air above the pad. See every test point and its Gauss value, at the height a body actually lies.

The FEI is proposing to cut the permitted PEMF field at its events from 1,000 Gauss to 100, and to require battery power. A battery limits the current a device draws continuously rather than the energy it stores between pulses, so it does not set the peak field.

Some PEMF companies leave the peak Gauss value off the product page because one value on its own misleads. The reasoning is sound, but a blank spec sheet leaves a buyer with nothing to compare. Here are four values to publish beside a peak.

PEMF spec sheets have started publishing a slew rate, usually in tesla per second. Here are the four facts that have to sit beside it before you can compare two devices.

One line of readings can't tell you if a PEMF accessory is stronger on one side. Here's how we scan four lines out from the center, and the five values that scan produces.

New in the 3D viewer: slice the measured field open with a movable cross-section, scrub the pulse to any moment, and set a full-scale person on the mat to see depth and coverage.