A positive displacement article sorter and method of monitoring a positive displacement article sorter, wherein the article sorter includes a frame, an endless web traveling in a longitudinal direction about the frame and an electric motor driving the endless web. The endless web is defined by a pair of continuous chains and a plurality of cross members connected at opposite ends with the chain. The positive displacement sorter includes a plurality of pusher shoes, each laterally traveling along at least one of the cross members. A sensing assembly is provided that has first and second portions. The first portion of said sensing assembly is positioned at the web. The second portion of said sensing assembly is positioned at a stationary location. The first portion of said sensing assembly is sensed with the second portion of the sensing assembly as the first portion of said sensing assembly travels about the frame. A parameter of the web is determined from an output of the sensing assembly.