This invention provides a linear actuator with a cylinder defining a cylinder axis. A piston is movable within the cylinder along the cylinder axis, and a piston rod extends axially from the piston for connection to a mechanism whereby in use, movement of the piston actuates the mechanism. A rotary output mechanism includes a rotary output element extending generally transversely from the cylinder and supported for rotation about an output axis generally normal to the cylinder axis. The rotary output mechanism is responsive to movement of the piston, and the rotary output element is adapted for operative engagement with an instrument mounted to the cylinder such that axial movement of the piston effects a corresponding rotational displacement of the rotary output element, whereby in use the instrument provides an output signal indicative of the position of the piston within the cylinder.