Velux: rain sensor

[Warichet]

Hi,

I've a couple of Velux rainsors, recup from a Velux Integra
Ref: WCM 531
Typ: 869008-01

The device has 3 wires (black,violet,grey), probably a +, - and an output (most probably not a dry contact)

I wonder if someone already managed to put such a sensor on KNX ?
if not, a schematic would already help a lot (not found on the net)

Thanks