Sensor placement for contact sensor?

I bought the following sensor.

The instructions say that I should put the main sensor on the frame (statoonary), and the magnet on the window (the moving part). Problem is, my window and frame size calls for it to be the other way around.

So my burning question is, is there a reason they specifically state that this way is “HIGHLY RECOMMENDED”? Does it not work as well the other way around?

It will work just as well either way. They are just telling you to put the non-breakable part (the magnet), on the movable object (the window) so you don’t have to worry about the sensor getting knocked off and breaking.

With these reed sensors, the smaller piece is literally just a magnet in a pretty plastic case. Then the other part Has a tiny metal sliver inside like a needle which is called “the reed,” and when the two pieces get close enough together, the magnet pulls the reed into contact Position inside the sensor and then the information gets transmitted to the hub.

So as long as they’re in the same relative positions to each other, it will always work. It’s just that the piece with the sensor is much more fragile, so they usually tell you to put it at the stationary position.


Agreed… I actually always put them the other way around; because there’s much more room on my doors (for the big electronic part) than the frame (where any magnet can be used).


Some sensors actually call for the installation to be the other way round. The ST one for instance has 3-way axis and vibration so its much more useful to have the sensor on the moving part and the magnet on the frame. No harm either way though.


thanks all.