[Jon Stratis]

You could place a limit switch such that it triggers when fully extended. Alternatively, you could get a cylinder with the magnetic option and utilize a magnetic reed switch on the cylinder itself to read the position when either extended or retracted. Basically, the reed switch straps to the side of the cylinder beer the top or bottom, and when a magnet inside the cylinder reaches it, it closes a contact that can be sensed through a digital input just like a limit switch.