Wiring a alarm sensor in an external garage

[ProjectBobcat]

Not sure if this question is best suited to this room or the electrics one but here goes..

I would like to wire up a extra motion sensor from my house alarm to the garage which is detached (approx 4metres from the house). I have a reel of cable that came with the alarm for the sensors, what is the correct way to run the cable bearing in mind it will be under the ground, can i put it in pvc tubing?

The existing feeds for the sockets/lighting circuits use armoured cables.

Thanks

 

[sparkymarka]

Fine in some 20mm conduit....

 

[ProjectBobcat]

Thanks

 

[EightyTwo]

Or blue water pipe...