Abstract: Apparatus for detecting and/or controlling tension of a moving web, for example, a filamentary tow, in a preselected zone of a longitudinal path traversed by the moving web. A sensing roller is journally supported by roller support structure, the latter having an opposing pair of deflection arms each of which is defined by edges which diverge from one another between inner supported and outer unsupported ends of the arms so that a region of reduced width (as measured in the general longitudinal direction of the web) is provided near each inner supported end. A reaction force which is indicative of the web's tension will thus be exerted against the sensing roller and transferred to the roller support structure so as to responsively cause the deflection arms to be resiliently flexed in the general direction of the reaction force.