Abstract: Systems, devices, and methods for monitoring the health of a mechanical system that includes a rotating shaft as disclosed can measure various parameters of the rotating shaft to assess health and performance of the mechanical system. A measuring device can rotate with the rotating shaft and can allow for strain to be measured in tension, which can provide for accurate rotating shaft parameter measurements with low cost and simple installation. The measuring device can include a connector that can couple to the rotating shaft, a bridge that can couple to the connector, and a strain-measuring sensor associated with the bridge such that the strain sensor can measure deformation of a portion of the bridge that can deform with rotation of the rotating shaft. The measuring device can be designed to amplify the strain experienced by the rotating shaft which can reduce noise in the strain measurement.