An apparatus includes a scanning head configured to move one or more sensors back and forth across a surface of a moving web of material. The apparatus also includes a vibration dampening device configured to reduce vibrations of the one or more sensors when the scanning head moves the one or more sensors back and forth across the surface of the web. The vibration dampening device includes at least one mass and one or more springs configured to create oscillatory movement of the at least one mass. The at least one mass and the one or more springs can be located within a housing that rides on a rail back and forth to move the scanning head across the surface of the web. The at least one mass and the one or more springs can also be located on a web deflector connected to the scanning head.