Closes near, opens far

Two distances, not one

Close the switch and the blades are touching, with a much smaller gap for the field to cross than when they were apart. It takes less field to hold them together than to pull them together. So the switch closes at one field and lets go at a lower one.

Start far away and slide the magnet in: the switch closes where the field reaches the pull-in. Now slide it back out slowly. It stays closed past that point, through the orange zone, and lets go only where the field has fallen far enough. Move back in from there and it stays open until the pull-in again. Inside the orange zone, the reading depends on which way the magnet came.

What the sheet promises

RMCIP's sheet for the MKA-14103 gives the release as a ratio: the switch lets go once the field has fallen to between 0.35 and 0.9 of what closed it. It does not say where in that range one switch falls, so plan for the widest gap. If a magnet's field falls as the cube of the distance, as a small magnet's roughly does away from its face, 0.35 of the field is 1.42 times as far: the switch can stay closed until the magnet is some 40 % farther away than where it closed.

The figure's millimetres belong to a model magnet that closes the switch at 15 mm. The ratio does not: it holds whatever the magnet.

Why this helps

The gap is called hysteresis, and it is the reason a slowly drifting magnet gives one clean change instead of flickering. Without it, a magnet sitting exactly at the threshold would close and open on every tremor. With it, the magnet has to move back a real distance before the switch changes its mind.

The cost is that "closed" does not mean "the magnet is as close as when it closed". For a door, set the magnet close enough that the door's normal shut position is well inside the closing distance, and a small opening takes it well past the letting-go distance.