Contact sensors?

[Paul Gale <groups2@xxxxxxxxxxxxxxxx>]

I have 3 large top opening velux windows in my loft and I ran alarm
cable to the bottom of each. I want to fit a suitable sensor to detect
when the window is open. Trouble is, the way that the window opens for
cleaning (whole window swivels 180deg from the center-ish of the
window) means that there's no clearance for positioning a standard
magnetic contact sensor between frame and window.

What I really need is a contact sensor that can operate around 50-70mm
ish between the magnet and reed switch. I've not seen anything like
this with that kind of operating gap.

Anyone got any ideas or know of suitable sensors ?

I guess there may be other sensor types that may be suitable although
of has to be fairly discreet (some kind of adjustable proximity
sensor). Adjustable operating distance would be really good as that
would allow fine-tuning.

Thanks,

Paul.

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