A laser piston position sensor for determining the position of a piston within an accumulator, the laser piston position sensor configured to attach to an end of the accumulator, and the accumulator having an aperture in the end thereof exposing the piston within the accumulator to the laser piston position sensor. The laser piston position sensor including a sensor housing enclosing a cavity containing a low pressure gas, and defining an opening from the cavity toward the accumulator, a laser sensor positioned within the cavity for emitting a laser toward the piston of the accumulator via the opening in the sensor housing and the aperture in the accumulator, and a transparent lens positioned between the laser sensor and the accumulator to allow passage of the laser from the laser sensor to the piston, and to separate gases in the accumulator from gases in the cavity of the sensor housing.